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Home My WebLink Aboutagenda.council.worksession.20170321 CITY COUNCIL WORK SESSION March 21, 2017 4:00 PM, City Council Chambers MEETING AGENDA I. Hunter Smuggler Drainage Master Plan II. Upcoming EOTC meeting discussion P1 MEMORANDUM TO: Mayor and City Council FROM : Jack Danneberg, E.I., Civil Engineer THRU: April Long, P.E., Stormwater Manager Trish Aragon, P.E., City Engineer DATE OF MEMO: March 17, 2017 MEETING DATE: March 21, 2017 RE: Smuggler-Hunter Master Plan Adoption BACKGROUND: A drainage master plan is a guidance document for long term planning of stormwater infrastructure. Master planning efforts are meant to identify areas with potential drainage problems and provide possible solutions. By addressing stormwater infrastructure design from a holistic large scale view, master plans maximize efficiency and minimize community impact. Drainage master plans are used by City of Aspen staff and citizens to make educated decisions regarding future development in the study area. During the creation of the City of Aspen Stormwater Program $350,000 was allocated for master planning efforts. To date, these funds have been used for new floodplain maps and an update to the Aspen Mountain Drainage Basin Master Plan (which was completed in 2006, prior to implementation of the stormwater program). In 2012, this funding was tapped to create a master plan for the Smuggler Hunter drainage basin, located on the north side of the Roaring Fork River between the Hunter Creek and Northstar preserve. The exact study area boundary is shown in Attachment A. The Smuggler Hunter drainage basin has very little regional drainage infrastructure but covers a large area with many residential units, and therefore is a prime candidate for installation of a regional storm system to minimize flood hazards. DISCUSSION: The goals of the Smuggler Hunter Master Plan, Attachment D, were to:  Identify potential flooding hazards.  Identify projects that improve public safety.  Identify areas and/or projects to improve stormwater quality.  Prioritize future projects using a cost benefit analysis.  Maximize efficiency through large scale long term planning. The national engineering consulting company URS was hired for the Smuggler Hunter master planning efforts. Using topographic, meteorological, and soils data; survey and site visits; and anecdotal information from staff and the public, URS did a hydrologic and hydraulic analysis of the designated study area. Existing streets, storm sewers, and detention facilities were analyzed for capacity. Rainfall, P2 I. mudflow and snowmelt (see below) were assessed as potential hazards. Design storms were routed through the study area with computer modeling classifying flood direction and depth. Problems identified through modeling and public outreach were used to plan for regional stormwater infrastructure. Rainfall: Apart from the short sections of pipe located in the Gibson Avenue Basin and Neale Avenue and OK Flats Basin, most of the drainage areas evaluated do not have any piped storm systems. Instead, stormwater and snowmelt runoff is conveyed by the streets, road side ditches and natural swales. Of the evaluated storm sewer systems that do exist and were surveyed, most were estimated to be able to convey the 5-year event or less. The City’s typical level of service has been the 10-year event. Therefore, most of the existing system falls short. Mudflow: The current Urban Runoff Management Plan mudflow section shows the upper reaches of the study area to be at risk of mudflow. This existing risk area was determined using a simple analysis based on slope and proximity to steep slope. For this master plan, a more detailed analysis was performed. FLO-2D modeling software was used to determine the level of risk the existing buildings face during a mudflow event. There were only a few isolated areas that were flagged as mudflow hazard zones by this more detailed mudflow analysis. Snowmelt: As most of regional precipitation comes in the form of snow, The City of Aspen saw it necessary to evaluate snowmelt for flooding hazard. Peak flow snowmelt rates were substantially less than rainfall peak flows for each snowmelt extreme temperature return period. By addressing drainage problems identified for rainfall runoff, drainage issues associated with snowmelt runoff should be lessened. Infrastructure: Drainage infrastructure projects were designed to address problems identified by public outreach and computer models. The proposed improvements were divided into 12 projects or individual storm systems serving basically 12 different areas, totaling approximately $3 million in needed infrastructure in 2013 dollars. Several criteria and weighting percentages were selected to prepare the preliminary ranking of the suggested projects. The criteria included reducing flooding hazards to public and private properties, improving public safety on major roadways and intersections, the opportunity to incorporate water quality improvements, and the ability to implement the improvements within the ROW (limited need for easements). The ranking and costs associated with each project are provided in Attachment B. Attachment B also references a basin or project area. Pages 1-4 represent those project areas and show the proposed infrastructure location and size and are included as Attachment C. FINANCIAL IMPLICATIONS: This plan is intended for planning purposes and there are no financial implications or obligations for the City by adopting this as a guidance document. Capital projects are being recommended by this document, but the implementation of these projects will be decided in future discussions. P3 I. The detailed hydrology and hydraulic modeling included in this master plan can be made available to the development community to assist with design of projects in the area, which should decrease the costs associated with preparing those designs. NEXT STEPS: The City of Aspen Engineering staff recommends that the Smuggler-Hunter Master Plan be adopted as an official document. Therefore, staff recommends presenting this document to Council and the public as an agenda item during an April Council Meeting. Once the Master Plan has been adopted by Council, staff will make the necessary updates to the Urban Runoff Management Plan and any other guidance documents affected by this information. In addition to the proposed capital project, the consulting team that completed this master plan recommended that Aspen implement the following:  Several drywells in the drainage area are plugged and in need of maintenance in order to properly function. Implement an inspection and maintenance program to improve the function of existing systems in the area.  Continue implementing water quality treatment as much as practicable throughout Aspen in accordance with the standards in Chapter 8 of the URMP.  Coordinate with Pitkin County and the Smuggler Mine to ensure that Smuggler Mountain Road is maintained with positive drainage to the existing cross culverts.  Many basins in this Master Plan have significant area within Pitkin County’s jurisdiction. Alternatives were proposed for those areas, but were not included in the conceptual design, per Aspen’s direction. Coordinate future improvement projects with Pitkin County to leverage funding and increase functionality by including the upstream areas.  Coordinate with existing and future land owners to align these proposed improvements with future development such as the private property within the Hunter Creek basin where proposed improvements will be tied to the single affected land parcel and will be the obligation of the land owner.  Phase capital infrastructure projects to minimize flood hazards in the study area. CITY MANAGER COMMENTS: Attachment A: Study Area Vicinity Map Attachment B: Proposed Capital Project Rank and Costs Attachment C: Pages 1-4 – Proposed Improvements Attachment D: Smuggler Hunter Master Plan P4 I. Attachment A: Study Area Vicinity Map P5 I. !!!!!! !!! !!!!!!!!! ! !!!!^_^_^_%O%O%O%O%O%ORoaringForkRiverHallam LakeHunterCreekRiversideDitchAstorMocklinSalvationSalvationUTEAVEEMAINSTECOOPERAVEEHOPKINSAVEG IB S O N A VE EDURANTAVEWFRANCISSTSPRUCESTNMILLSTPARKCIRWHALLAMSTN1STSTPA RK AVE DEANSTE L U PI N E D R M T N L A U R E L D R LAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERDSHUNTERSTSWESTENDSTVINESTNEALEAVENSPRINGSTUTEPLS H A D Y L N SMILLSTS1STSTEHYMANAVEEASTWOODDRKINGSTEBLEEKERSTSGALENASTWESTVIEWDRRIOGRANDEPLWATERSAVEDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTSKIMMINGLNSESAMESTARDMOREDREHALLAMSTW L U P I N E D R AJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRRIVERSIDEDRSRIVERSIDEAVEWILLI AMS W AY CRYSTALLAKERDCOTTONWOODLNTFABILOOPMTNLAURELCTMASCOTTELNALICELNSSPRINGSTSSPRINGSTSGALENASTStillwater Bridge BasinEastwood BasinRiverside McSkimming BasinNeale Avenue and OK Flats BasinHunter Creek BasinGibson Avenue Basin"Hunter Creek BasinN. Spring St.Aspen Art Museum ParkSnyderParkHerron ParkGibson Ave.Garrison ParkJohnson ShaftUnknown SourceMollie Gibson Shaft8100 90009 1 0 0 92009 3 0 0 94009 5 0 0 9 6 0 09700 98 00 800010300104007900102001010010000870086001050099008500830084008200880010600890078008 4 0 0 91008 1 0 01030010200 82008 6 0 0 81008900 8300990090008 6 0 0 8 9 0 0 8000103001 0 1 0 0 96008 3 0 0 9700790096008600950010100100008 2 0 09800 800091009 2 0 010000840080008000 8 7 0 0 8 0 0 0 8 50095008 5 0 0 8 8 0 0 01,000FeetoMajor DrainageArea MapSmuggler/Hunter SurfaceDrainage Master Plan2.1T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-01 Major Drainage Basinsr90.mxd Plot Date: 1/9/2015Legend^_Mine Flow Sources%OPotential Water Quality Locations!!Irrigation Ditch, CulvertIrrigation Ditch, OpenTopographic Contour(feet NGVD29)Study Area BoundaryWetland AreasRiparian AreasSurface WaterMajor BasinsEastwood BasinGibson Avenue BasinHunter Creek BasinNeale Avenue and OK Flats BasinRiverside McSkimming BasinStillwater Bridge BasinP6I. Attachment B: Proposed Capital Project Rank and Costs P7 I. Attachment B: Smuggler Hunter Master Plan ‐ Proposed Capital Projects Rank and CostsRank Total(1 to 12) ProjectCost1Gibson Avenue Main Stem, N17 Branch, & G09 BranchCombined Gibson Avenue and Neale Avenue and OK Flats Basins$540,000 Prevents flooding of properties, high possibility to combine with wq improvements2 E. Hopkins Outfall North Branch Riverside McSkimming Basin $187,000 Prevents flooding of properties, possible to combine with wq improvements3 Oklahoma Flats Outfall Neale Avenue Basin $54,000 4 E. Hopkins Outfall South Branch Riverside McSkimming Basin $199,000 5 Williams Woods Proposed System Hunter Creek Basin $186,000 6 Neale Avenue Storm System Neale Avenue Basin $123,000 Completed as part of Neale Ave SW, traffic calming, and ped improvement project. Final cost for sw pipe?7 Eastwood Main System Eastwood Basin $258,000 Prevents flooding of Hwy 82, possible cost-sharing with CDOT and County8E. Cooper Avenue Outfall, Mildland and Cooper Branch, & McSkimming BranchRiverside McSkimming Basin $546,000 $150K in easements. Most important piece is the downstream end which could be done as part of a water quality improvement project at Anderson Park. 9 Lone Pine Rd. Outfall Gibson Avenue Basin $169,000 10 King Street Branch Neale Avenue Basin $43,000 11 River Bluff Townhomes Branch Gibson Avenue Basin $147,000 $112K in easements.12 Brown Ln. Branch and N12 BranchCombined Gibson Avenue and Neale Avenue and OK Flats Basins$533,000 $381K in easements$2,985,000 Ranking considered reduction of flooding to properties (cost of project as relates to value of property protected), improvements to public safety, opportunities to incorporate wq improvements, requirement of an easementBiggest BenefitsTOTALNote: All costs are in 2013 dollars.Proposed Stormwater Projects Basin Notes/Comments P8I. Attachment C: Pages 1‐4 – Proposed Improvements P9 I. !!!!!!!!!!!!!!!!!! !!!! ! !%, %, %O %O HunterCreek RoaringForkRiver People have to sandbag Basement flooding in 2006 storm. Gibson Ave. Aspen Art Museum Park SalvationM o c k l i n M o c k l i n Mocklin M o ck lin Hunter Creek Basin Hunter Creek Basin REDMTNRDSPRUCESTLONEPINERD VINESTGIBSONAVE TEALCTNMILLSTSPRUCECTWILLIAMSWAYRACESTBROWNLNS H A D Y L N PUPPYSMI THSTNSPRI NGSTCOWENHOVENCTWALNUT ST BRENDENCTOFALL-13 OFALL-12 OFALL-11 0 200 Feet o Suggested Plan Hunter Creek Basin 10-Year Conveyance Alternative Page 1 of 4 Smuggler/Hunter Surface Drainage Master Plan T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-02PublicMeeting\HunterAlternativer90.mxdPlotDate:2/25/2015InfoSWMM Elements Outfall Existing Surface Flow Existing Pipe Legend %,Known Deficiencies %O Potential Water Quality Locations Proposed 18" Pipe Easement !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Major Basins Existing 100-yr Floodplain P10I. !!!!!!!!!!!!!!!!!! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! ! ! ! !!!%, %, %, %, %, ^_ ^_ ^_ %O %O %O %O %O SO U TH AVE RoaringForkRiver GIBSONAVE PARKCIREHOPKINSAVE SMUGGLERMTNRDSPRUCESTSILVERLODEDROAKLNLONEPINERD PARKAVENSPRINGSTNEALEAVE VINEST SSPRINGSTEMAINST KINGSTMAPLELNRACEST SORIGINALSTTEALCTAJAXAVEMIDLANDAVENI CHOLASLNQUEEN STWALNUTST COTTONWOODLNRIOGRANDEPL WILLIAMSRANCHDRWILLIAMSWAYMASCOTTE LN BAYST FREESI LVERCTCOWENHOVENCTEFRANCISST EBLEEKERST MATCHLESSDRHAROLDROSSCTREGENTSTBRENDENCTNSPRINGSTPeople have to sandbag Dry well plugged and floods System needed to drain low spot Basement flooding in 2006 storm. Flooding during snowmelt. Speed hump is dam. OFALL-8 OFALL-7 OFALL-6 OFALL-2 OFALL-5 OFALL-4 OFALL-3 OFALL-1 Neale Avenue and OK Flats Basin Gibson Avenue Basin Gibson Ave. Herron Park Garrison Park N. Spring St. Aspen Art Museum Park Johnson Shaft Unknown Source Mollie Gibson ShaftSalvat i onAstorMoc kl i nM o c k l i nMocklinMocklin 0 300 Feet o Suggested Plan Combined Gibson Avenue Basin and Neale Avenue & OK Flats Basin10-Year Conveyance Alternative (With Limited Easements) Page 2 of 4 Smuggler/Hunter Surface Drainage Master Plan T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-02PublicMeeting\GibsonNealAlternativer90.mxdPlotDate:2/25/2015InfoSWMM Elements Outfall Existing Surface Flow Existing Pipe Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Proposed 18" Pipe Proposed 24" Pipe Proposed 36" Pipe Easement !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Major Basins Existing 100-yr Floodplain P11I. !!!!!!! ! ! ! ! ! !!!%, %, %, ^_%O %O %O ECOOPERAVE PARKAVEMCSKI MMI NGRDSWESTENDSTUTEPLMIDLANDAVEEASTWOOD DR KINGST WESTVIEW DR WATERSAVE SKIMMINGLNROARINGFORK DRARDMOREDR WLUPI NEDRNORTHWAYDRRIVERSIDEDRSRIVERSIDEAVEASPEN GROVE RD QUEENST CLEVELANDSTCRYSTAL LAKE RDFREDLNMASCOTTELN DALEAVE ARDMORECTALICELNALPINE CTNRIVERSIDEAVELACETCT EHOPKINSAVE EHYMANAVE System needed in area Dry well plugged and floods Snyder Park Herron Park Garrison Park Unknown Source RoaringForkRiverSal vat i onRiversideDitchAstor Riverside McSkimming Basin OFALL-14 OFALL-10 OFALL-09 OFALL-08 OFALL-07 OFALL-06 OFALL-DW01-R07 0 300 Feet o Suggested Plan Riverside McSkimming Basin 10-Year Conveyance Alternative (With Limited Easements) Page 3 of 4 Smuggler/Hunter Surface Drainage Master Plan T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-02PublicMeeting\RiversideAlternativer90.mxdPlotDate:2/25/2015InfoSWMM Elements Outfall Existing Surface Flow Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Proposed 18" Pipe Proposed 24" Pipe Easement !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Major Basins Existing 100-yr Floodplain P12I. RoaringForkRiver HWY82MTNLAURELDREASTWOODDR WESTVIEW DR ROARING FORK DR NORTHWAYDRSTILLWATERLN STILLWATERDRASPEN GROVE RD FABILOOPMTNLAURELCTMCSKIMMINGRD CRYSTALLAKERDMCSKIMMING RD ALICELNLUPINEDRWLUPINEDRELUPI NEDROFALL-2 OFALL-1 OFALL-01 OFALL-02 Sal vat i onEastwood Basin Stillwater Bridge Basin 0 250 Feet o Suggested Plan Combined Stillwater Bridge Basin and Eastwood Basin 10-Year Conveyance Alternative (Without Easements) Page 4 of 4 Smuggler/Hunter Surface Drainage Master Plan T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-02PublicMeeting\StillwaterEastwoodAlternativer90.mxdPlotDate:2/25/2015InfoSWMM Elements Outfall Existing Pipe Legend Proposed 18" Pipe Proposed 24" Pipe Proposed 30" Pipe Irrigation Ditch, Open Study Area Boundary Major Basins Existing 100-yr Floodplain P13I. Attachment D: Smuggler Hunter Master Plan P14 I. 100% SUBMITTAL DRAFT REPORT SMUGGLER/HUNTER SURFACE DRAINAGE MASTER PLAN PREPARED FOR: DEPARTMENT OF ENGINEERING – STORMWATER PROGRAM 130 SOUTH GALENA STREET ASPEN, COLORADO 81611 APRIL 10, 2015 PREPARED BY: URS Corporation 8181 East Tufts Avenue Denver, Colorado 80237 P15 I. P16 I. TABLE OF CONTENTS April 2015 i | Table of Contents Executive Summary ...................................................................................................................................... i Section 1 Introduction ..................................................................................................................... 1-1 1.1 Authorization ........................................................................................... 1-1 1.2 Purpose & Scope ...................................................................................... 1-1 1.3 Mapping and Surveys .............................................................................. 1-3 1.4 Analysis and Design Criteria ................................................................... 1-3 1.5 Acknowledgments.................................................................................... 1-4 Section 2 Stormwater Runoff and Drainage Facility Capacity Analysis ..................................... 2-1 2.1 Introduction .............................................................................................. 2-1 2.2 Study Area ............................................................................................... 2-1 2.3 Mine Flows and Irrigation ....................................................................... 2-1 2.4 Water Quality Area Assessment .............................................................. 2-5 2.5 Hydrology ................................................................................................ 2-6 2.5.1 CUHP Analysis ............................................................................ 2-7 2.5.2 Hydrograph Routing .................................................................. 2-22 2.6 Hydraulics .............................................................................................. 2-25 2.6.1 Modeling Criteria ....................................................................... 2-25 2.6.2 Open Channels ........................................................................... 2-26 2.6.3 Culverts ...................................................................................... 2-26 2.6.4 Storm Sewers ............................................................................. 2-26 2.6.5 Floodplain Modeling .................................................................. 2-26 2.7 Drainage System Capacity ..................................................................... 2-35 2.7.1 Summary by Basin ..................................................................... 2-35 2.8 Discussion .............................................................................................. 2-52 Section 3 Mudflow Analysis .......................................................................................................... 3-1 3.1 Scope of Work ......................................................................................... 3-1 3.2 Relevant Studies and Material ................................................................. 3-1 3.3 Characteristics of Mudflow and Mud Flood ............................................ 3-2 3.4 Site Investigation and Critical Watershed Identification ......................... 3-4 3.4.1 Hunter Creek Basin ...................................................................... 3-5 3.4.2 Gibson Avenue Basin .................................................................. 3-5 3.4.3 Neale Avenue and OK Flats Basin .............................................. 3-5 3.4.4 Riverside McSkimming Basin ..................................................... 3-6 3.4.5 Eastwood Basin ............................................................................ 3-6 3.4.6 Stillwater Bridge Basin ................................................................ 3-6 3.4.7 Summary ...................................................................................... 3-9 3.5 FLO-2D .................................................................................................... 3-9 3.5.1 Introduction .................................................................................. 3-9 3.5.2 Methodology and Assumptions ................................................. 3-10 3.5.3 Input Data for FLO-2D Models ................................................. 3-10 P17 I. TABLE OF CONTENTS ii | Table of Contents April 2015 3.5.4 Modeling Scenarios ................................................................... 3-13 3.5.5 Mudflow Hydrographs and Initiation Locations........................ 3-13 3.6 FLO-2D Modeling Results .................................................................... 3-15 3.6.1 2-Year Mudflow Event .............................................................. 3-15 3.6.2 10-Year Mudflow Event ............................................................ 3-16 3.6.3 50-Year Mud Flood Event ......................................................... 3-16 3.6.4 100-Year Mud Flood Event ....................................................... 3-16 3.6.5 Yellow Zones ............................................................................. 3-16 3.7 Discussion .............................................................................................. 3-16 Section 4 Snowmelt Analysis ......................................................................................................... 4-1 4.1 Introduction .............................................................................................. 4-1 4.1.1 Theory .......................................................................................... 4-1 4.1.2 Extreme Temperature-Frequency Analysis ................................. 4-1 4.1.3 Snowmelt Coefficient, Ks, and Elevation Lapse .......................... 4-5 4.1.4 Model Inputs ................................................................................ 4-7 4.1.5 Results and Discussion ................................................................ 4-8 Section 5 Alternative Development ................................................................................................ 5-1 5.1 Introduction .............................................................................................. 5-1 5.2 Goals, Criteria, and Constraints ............................................................... 5-1 5.2.1 Flood Impacts ............................................................................... 5-2 5.2.2 Cost Effectiveness ........................................................................ 5-2 5.2.3 Implementation ............................................................................ 5-2 5.3 Conceptual Alternatives ........................................................................... 5-2 5.3.1 Detention ...................................................................................... 5-3 5.3.2 Conveyance .................................................................................. 5-4 5.3.3 Easements .................................................................................... 5-4 5.4 Stormwater Alternatives .......................................................................... 5-4 5.4.1 Hunter Creek Basin ...................................................................... 5-5 5.4.2 Gibson Avenue Basin .................................................................. 5-5 5.4.3 Neale Avenue and OK Flats Basin .............................................. 5-6 5.4.4 Combined Gibson Avenue and Neale Avenue & OK Flats Basins Conveyance Alternatives .................................................. 5-7 5.4.5 Riverside McSkimming Basin ..................................................... 5-8 5.4.6 Combined Eastwood and Stillwater Bridge Basins Conveyance Alternatives ........................................................... 5-10 5.5 Alternative Cost Estimates ..................................................................... 5-28 5.6 Discussion and Recommendations ........................................................ 5-33 Section 6 Conceptual Design ......................................................................................................... 6-1 6.1 Conceptual Design Overview .................................................................. 6-1 6.2 General Recommendations ...................................................................... 6-1 P18 I. TABLE OF CONTENTS April 2015 iii | Table of Contents 6.3 Operations and Maintenance Recommendations ..................................... 6-1 6.4 Prioritizing and Phasing ........................................................................... 6-2 6.5 Final Proposed Costs................................................................................ 6-7 6.6 Selected Projects by Basin ....................................................................... 6-7 6.6.1 Combined Gibson Avenue and Neale Avenue & OK Flats Basins 10-year Conveyance Alternative ...................................... 6-7 6.6.2 Riverside McSkimming Basin 10-year Conveyance with Limited Easements Alternative .................................................... 6-8 6.6.3 Combined Eastwood and Stillwater Bridge Basins 10-year Conveyance with No Easements Alternative ............................... 6-9 Section 7 References ...................................................................................................................... 7-1 List of Tables Table 2.1 Mine Shaft Locations Table 2.2 Irrigation Diversions/Ditches Table 2.3 Model Components Table 2.4 Aspen, Colorado Design Rainfall Depths Table 2.5 Recommended Horton’s Infiltration Rates for Different Soil Groups (UDFCD 2001) Table 2.6 Adopted Land Use Characteristics and Parameter Values (Based on the Guidelines from the URMP and USDCM Volume 1) Table 2.7 CUHP 2005 Results – Sub-basin Peak Outflow Table 2.8 InfoSWMM Model Elements Table 2.9 Manning’s N-Values for Conveyance Elements Table 2.10 Floodplain Assessment by Sub-basin Table 2.11 Rainfall Summary Tables Table 2.12 Determined WQCV Watershed Depth for Percentages of the Total WQCV Table 2.13 WQCV Summary Tables Table 3.1 Mudflow Behavior as a Function of Sediment Concentration Table 3.2 Overland Flow Manning’s Roughness Values1 Table 3.3 Yield Stress and Viscosity as a Function of Sediment Concentration Table 4.1 Monthly Statistics for Temperature and Precipitation in Aspen (Original Table 2.1 in URMP) Table 4.2 Daily Temperature Frequency Analysis for April in Aspen, Colorado Table 4.3 Daily Temperature-Frequency Distributions P19 I. TABLE OF CONTENTS iv | Table of Contents April 2015 Table 4.4 Temperature-Frequency in April for Each Elevation Band within the Study Area in Aspen, Colorado Table 4.5 Snowmelt Coefficient-Frequency in April for Each Elevation Band within the Study Area in Aspen, Colorado Table 4.6 Snowmelt Summary Tables Table 5.1 Basic Flood Control Alternatives Table 5.2 Proposed Detention Pond Effectiveness Table 5.3 Alternatives Summary Tables Table 5.4 Alternative Cost Estimates Table 5.5 Proposed Project Costs by Watershed (2013 Dollars) Table 6.1 Project Ranking Matrix Table 6.2 Stormwater Capital Improvements Phasing 2016-2026 Table 6.3 Final Proposed Project Costs for Aspen by Watershed (2013 Dollars) List of Figures Figure 1.1 Vicinity Map Figure 2.1 Major Drainage Area Map Figure 2.2 CUHP Frequency Storm Rainfall Depth Distribution for Aspen, Colorado Figure 2.3 Drainage Basins & SWMM Routing Elements (Sheets 1-6) Figure 2.4 Hydrologic Soil Groups Figure 2.5 Initial Soil Infiltration Rates Figure 2.6 Existing Land Use Figure 2.7 Problem Areas (Sheets 1-6) Figure 3.1 Mud Slide, May 8, 2008 Figure 3.2 Hyperconcentrated Sediment Flow Classification (after National Research Council 1982) Figure 3.3 Site Investigation and Critical Watersheds Figure 3.4 Map of Potential Geologic Hazards Figure 3.5 Locations of the Inflow Cells in the FLO-2D Models Figure 3.6 Maximum Mudflow Depth 2-year Event Figure 3.7 Maximum Mudflow Depth 10-year Event Figure 3.8 Maximum Mudflow Depth 50-year Event Figure 3.9 Maximum Mudflow Depth 100-year Event Figure 3.10 Mudflow Hazard Yellow Zones P20 I. TABLE OF CONTENTS April 2015 v | Table of Contents Figure 4.1 Average Daily Snow Water Equivalence Depths from Aspen Weather Station 050372 Figure 4.2 Daily Temperature-Frequency Distributions Figure 4.3 Elevation Bands in the Study Area in Aspen, Colorado Figure 5.1 10-year Hunter Creek Basin Conveyance Alternative Figure 5.2 10-year Combined Gibson Avenue Basin and Neale Avenue & OK Flats Basin Conveyance Alternative (with Limited Easements) Figure 5.3 10-year Riverside McSkimming Basin Conveyance Alternative (with Limited Easements) Figure 5.4 10-year Combined Stillwater Bridge Basin and Eastwood Basin Conveyance Alternative (without Easements) List of Appendices (With the exception of Appendix G all appendices are provided on enclosed CD) Appendix A Site Investigation Photographs Appendix B Rainfall-Runoff Analysis Appendix C Mudflow Analysis Appendix D Snowmelt Analysis Appendix E Alternatives Analysis Appendix F Cost Estimates Appendix G Conceptual Plans P21 I. LIST OF ACRONYMS AND ABBREVIATIONS vi | List of Acronyms and Abbreviations April 2015 % percent °F Degrees Fahrenheit ac acre ASE Aspen/Pitkin County Airport Aspen City of Aspen ASTM American Society for Testing and Materials ATI Antecedent Temperature Index CDOT Colorado Department of Transportation CDSS Colorado Decision Support System CMP corrugated metal pipe cfs cubic feet per second CUHP Colorado Urban Hydrograph Procedure FEMA Federal Emergency Management Agency GIS geographical information system gpm gallons per minute HDPE high density polyethylene HEC-RAS Hydrologic Engineering Centers River Analysis System HGL hydraulic grade line ID identification inch/hr inches per hour IND Mining LOWRES Low Density Residential Master Plan Surface Drainage Master Plan MFRES High Density Residential MRES Medium Density Residential NOAA National Oceanic and Atmospheric Administration NRC National Research Council NRCS National Resources Conservation Service OS Open Space PARK Parks & Cemeteries PDF portable document format P22 I. LIST OF ACRONYMS AND ABBREVIATIONS April 2015 vii | List of Acronyms and Abbreviations PVC polyvinyl chloride RCP reinforced concrete pipe SSURGO Soil Survey Geographic SWMM Storm Water Management Model SWMM 5 EPA SWMM 5 model tc time of concentration UDFCD Urban Drainage and Flood Control District URMP Urban Runoff Management Plan URS URS Corporation USACE United States Army Corps of Engineers USDA United States Department of Agriculture USDCM Urban Storm Drainage Criteria Manual USEPA United States Environmental Protection Agency USGS United States Geological Survey WQCV Water Quality Capture Volume WRC WRC Engineering, Inc. P23 I. viii | List of Acronyms and Abbreviations April 2015 This page intentionally left blank P24 I. EXECUTIVE SUMMARY April 2015 ES-i | List of Acronyms and Abbreviations 1 Executive Summary The Smuggler/Hunter Surface Drainage Master Plan (Master Plan) is a planning study authorized by the City of Aspen, Colorado, in an agreement with URS Corporation (URS) dated June 4, 2012. The study area, shown in Figure ES.1, lies to the east of the Roaring Fork River and includes watershed area on Smuggler Mountain to the southeast of Hunter Creek. The study area encompasses portions of the City of Aspen (Aspen) and unincorporated Pitkin County. The sponsoring agency of this study is Aspen. The objective of the planning study was to perform hydrologic, hydraulic, and mudflow evaluations of the area shown on Figure ES.1 and to document the existing storm drainage patterns, structures, and facilities throughout the Smuggler/Hunter area of Aspen. The results of these evaluations were used to prepare recommendations for future improvements, conceptual designs, and cost estimates that address water quantity, water quality, and mudflow issues. The primary tasks of this project were to: • Inventory the existing stormwater infrastructure and update the existing geographical information system (GIS) data • Develop and execute hydrologic and hydraulic models • Identify problem areas • Identify potential locations for stormwater quality facilities • Evaluate potential debris and mudflow areas • Identify mine water outflows and evaluate their impacts on the stormwater conveyance system • Evaluate and document the capacity of irrigation ditches and facilities • Recommend capital improvement projects, provide conceptual designs and a capital plan to reduce or eliminate drainage and flooding problems with available resources • Develop a Master Plan focused on conveyance and water quality improvements, as well as addressing mudflow potential Generally, the overall objectives of implementing drainage and flood control alternatives in Aspen are to: 1. Remove buildings from the 100-year floodplain and reduce flooding. 2. Improve public safety. 3. Improve stormwater quality. 4. Limit costs by reducing land acquisition needed for easements. 5. Leverage cost sharing opportunities. P25 I. ES-ii | Executive Summary April 2015 P26I. April 2015 ES-iii | List of Acronyms and Abbreviations STUDY AREA Aspen lies within Pitkin County in Township 10 South, Range 85 West of the 6th Principal Meridian. The selected study area (Study Area) within the corporate limits of Aspen mainly lies in the valley and east bench of the Roaring Fork River that runs from the southeast to the northwest along the base of the south side of Smuggler Mountain. The total study area is approximately 0.5 square mile with elevations ranging from approximately 7,830 feet to 10,460 feet. Surface runoff from the majority of the Study Area flows through the developed areas of Aspen on Smuggler Mountain before emptying into the Roaring Fork River. A small portion of the Study Area contributes flow to Hunter Creek, which then empties into the Roaring Fork River. The six major drainage basins and Study Area are shown on Figure ES.2. MINE FLOWS AND IRRIGATION With the presence of the Smuggler Mine, several historic mining shafts, and several irrigation ditches in the Study Area; there is potential that stormwater flows and drainage patterns may be impacted by these facilities. While the Aspen Water Department monitors flow rate and depth in several ditches, including mine flow locations, they do not monitor water quality as it is not required by the State of Colorado. Therefore, the water quality of the mine flows is unknown. During the site investigation for mine and irrigation flows on October 8, 2012, groundwater flows were observed to be coming from three locations that were corroborated as mine flows by Aspen staff. The three sites are shown in Figure ES.2. The five ditches which flow through the Study Area are shown in Figure ES.2. Two of the ditches are for irrigation while the other three are mine shaft outflows. Irrigation ditches are typically designed along flat slopes and with only the capacity needed to convey the decreed flow for the ditch with no capacity to accept stormwater flows; nor would such carrying capacity be guaranteed, as most ditches are privately owned. Therefore, irrigation ditches were ignored for the purposes of the stormwater rainfall-runoff analysis in this study, consistent with the Colorado Water Conservation Board’s stormwater management policy, UDFCD’s drainage policies, and the 1998 Drainage Facility Capacity Analysis for Aspen. WATER QUALITY AREA ASSESSMENT As part of the drainage capacity analysis, the URS team conducted field assessments of wetlands and riparian areas and of potential water quality pond locations within the Smuggler/Hunter study area. Understanding location and the existence of wetland and riparian areas is critical to stormwater planning to account for the natural water quality treatment associated with such areas as well as to avoid adversely impacting the areas with future planned facilities. Further, understanding where future water quality facilities may be planned on publically-owned lands is a first step to being able to viably include such facilities in a Master Plan, especially in a locale such as Aspen, where land values are at a premium. Identified wetlands and riparian areas and water quality pond locations were delineated in GIS and are shown on Figure ES.2. Photos of the wetlands and riparian areas investigation are included in Appendix A. Riverside areas with any existing wetland areas are located on the P27 I. ES-iv | Executive Summary April 2015 uppermost reaches of the Roaring Fork River and then the lowermost reaches within the study area, including parts of Hunter Creek. The field assessment of potential water quality pond locations was conducted with Aspen staff on July 23, 2012. Six potential sites for the possible location of future water quality facilities were identified, as follows: Aspen Art Museum Park, Herron Park, Garrison Park, Snyder Park, the “pocket park” at the south end of North Spring Street, and an area along the roadway right- of-way east of the intersection of Gibson Avenue and Red Mountain Road. RAINFALL-RUNOFF ANALYSIS Per Chapter 3 of Aspen’s URMP, the Rational Method, Colorado Urban Hydrograph Procedure (CUHP), and EPA’s Storm Water Management Model (SWMM) are recommended for watershed hydrologic modeling and runoff estimation. The Rational Method is a simplified hydrologic method only developed for peak flow prediction in basins less than 90 acres. In this study, runoff hydrographs were estimated using CUHP 2005 software, version 1.4.4, with UDFCD’s recommended methodology for estimating rainfall infiltration losses, which is Horton’s Method. The CUHP runoff hydrographs were routed using InfoSWMM, a highly- developed, well-supported hydrologic/hydraulic modeling software that implements the EPA SWMM analysis methods in a fully GIS-integrated environment and produces models and output compatible with EPA SWMM 5.0. The recommended kinematic wave approach was used for routing flows. Soils data in the study area dictates the fraction of precipitation that ultimately becomes runoff. As Aspen’s soil map provided in the URMP did not provide full coverage of the study area, the Soil Survey Geographic (SSURGO) database for Pitkin County circa 2008 was used. Land use data were applied to develop the hydrologic parameters required by CUHP, by delineating the impervious percentages based on Aspen zoning, Pitkin County zoning, designated open space, and parcel data, as well as site visits and aerial photography (2008) provided by Aspen. The imperviousness parameters for each sub-basin were estimated as composite values resulting from a weighted-area average computation using the recommended parameter values. Based on discussions with Aspen, the watersheds are built-out and will mostly experience in-fill development in the future; therefore, no land use characteristics for future build-out conditions were estimated. Hydraulic analyses were conducted for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence interval flood events for each major basin shown in Figure ES.2. Open channels were analyzed using InfoSWMM and Manning’s equation. Culverts were analyzed using InfoSWMM and FlowMaster. Storm sewers were analyzed using InfoSWMM. Where the capacity of a surface flow conduit (a street section, for example) was exceeded or where flows are conveyed in unconfined surface flow paths, the need for floodplain modeling was assessed. For those ares meeting the assessment criteria, floodplains were modeled using FlowMaster and HEC-RAS. The hydrologic and hydraulic analyses for rainfall-runoff resulted in an assessment of system capacity and identification of problem areas. P28 I. !!!!!!! !!!!!!!!!!!!!! ! ! ^_ ^_ ^_ %O %O %O %O %O %ORoaring Fo r k R i v e r Hallam Lake Hunter CreekRiverside DitchAstorMocklin Salvation Sal v a t i on U T E A V E E MAIN S T E COOPE R A V E E HOPKIN S A V E GI B SO N A V E E DURAN T A V E W FRANC I S S T SPRUCE STN MILL STPARK CIRW HALLA M S T N 1ST STPARK AVEDEAN ST E LUP INE DRMTN LAURE L DRLAKE AVES ASPEN STS ORIGINAL STS MONARCH STOAK LN LONE P I N E R D S HUNTER STS WEST END STVINE ST NEALE AVEN SPRING STUTE PLSHADY LNS MILL STS 1ST STE HYMAN A V E EASTWOOD DR KING S T E BLEEK E R S T S GALENA STWESTVIEW DR RIO GRANDE PL WATERS A V E NORTHSTAR DRMAPLE LNS GARMISCH STS ALPS RDASPEN MTN RDRACE STSKIMMING LNSESAME STARDMORE DRE HALLA M S T W LUP INE DRAJAX AVEBROWN LNNORTHWAY DRSTILLWATER DRRIVERSIDE DRS RIVERSIDE AVEWILLIAMS WAYCRYSTAL LAKE RDCOTTONWOOD LN PEARL CT FABI LO O P MTN LAUREL CTMASCOTTE LN ALICE LNS SPRING STS SPRING STS GALENA STStillwater Bridge Basin Eastwood BasinRiverside McSkimming Basin Neale Avenue and OK Flats Basin Hunter Creek Basin Gibson Avenue Basin"Hunter Creek Basin N. Spring St. Aspen Art Museum Park SnyderPark Herron Park Gibson Ave. Garrison Park Johnson Shaft Unknown Source Mollie Gibson Shaft 810 0 90009 1 0 0 9 2 0 09300940095009600970098008000 10300104007900 102001010010000 8700 8600 105009900 8500 8300 8400 8200 8800 106008900 7800 840 0 91008 1 0 0 10300102008 2 0 0 8600810 0 8900 8300 9900 900086008 9 0 08000 10300101009600 8 3 0 0 97007900 96008600 9 5 0 010100100008 2 0 0 9800 8000 9100920010000840080008 0 0 0 870080008500 950085 0 0 8 8 0 0 0 1,000Feet o Major DrainageArea Map Smuggler/Hunter SurfaceDrainage Master Plan ES.2 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-01 Major Drainage Basinsr90.mxd Plot Date: 4/8/2015Legend ^_Mine Flow Sources %O Potential Water Quality Locations ! !Irrigation Ditch, Culvert Irrigation Ditch, Open Topographic Contour(feet NGVD29) Study Area Boundary Wetland Areas Riparian Areas Surface Water Major Basins Eastwood Basin Gibson Avenue Basin Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Stillwater Bridge Basin P29I. P30I. ES-vi | Executive Summary April 2015 MUDFLOW ANALYSIS Review of geologic and topographic conditions, records of the mud slide that occurred in May 2008, and site observation on October 9-10, 2012, identified three critical watersheds with potential mudflow hazard. They are Hunter Creek Basin, Gibson Avenue Basin, and Neale Avenue and OK Flats Basin in the Study Area. The FLO-2D two-dimensional model was used to estimate the extent of the mudflow hazard areas. The risk of mudflows and mud floods were accounted for by applying the bulking factors, mudflow viscosity, and yield shear stress to the clear-water hydrographs. Four scenarios were analyzed in this study. They are the mudflow events from the 2- and 10- year storm events, and the mud flood events from the 50- and 100-year storm events. Figures ES.3 to ES.6 in show the simulated maximum depth of mudflow for each modeling scenario. The delineated mudflow areas agree in general with the observed mud slide event along Spruce St. in May 2008. In addition, the yellow mudflow zones where the mudflow depth is greater than 2 ft on the 100-year mudflow inundation map were delineated and are shown in Figure ES.7. Due to the uncertainty of the data and the modeling assumptions, the computed mudflow depths provided by the FLO-2D model should be considered as qualitative values rather than absolute values. SNOWMELT ANALYSIS Aspen experiences sufficient snowfall throughout the fall, winter, and spring seasons to accumulate a significant snow pack both in the urban parts of town as well as in the headwaters of watersheds. Melting of this snow pack releases large volumes of water and is a stormwater runoff condition that must be evaluated so the impacts to the drainage systems, roadways, structures and facilities in the Study Area are understood and improvements can be recommended if needed. The EPA SWMM 5 model was used to compute snowmelt runoff from each sub-basin by using the degree-day method approach which is included in the SWMM 5 model interface. Input data for the snowmelt analysis includes time series data of air temperature, snowmelt coefficients, and snow water equivalent snow pack for each sub-basin. Peak flow snowmelt rates were substantially less than rainfall peak flows for each snowmelt extreme temperature return period. Although peak snowmelt runoff is not a threat relative to rainfall runoff values, snowmelt cumulative volume can pose a flooding threat in areas without engineered drainage systems. P31 I. April 2015 ES-vii | List of Acronyms and Abbreviations This page intentionally left blank P32 I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST SPRUCE ST SPRUCESTBROWNLN"Smuggler Mine On-Site Pond8110 830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 8420801079707870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 78607 9 3 0 86607930 7 9 0 0 788078507900 84307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 2-Year Event Smuggler/Hunter Surface Drainage Master Plan ES.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-06 Mudflow 2 year.mxd Plot Date: 4/10/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P33I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST SPRUCE ST SPRUCESTBROWNLN"Smuggler Mine On-Site Pond 8110830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 7900 8 0 9 0 842079707870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 8370832078907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 78607 9 3 0 86607930 7 9 0 0 788078507900 84307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 10-Year Event Smuggler/Hunter Surface Drainage Master Plan ES.4 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-07 Mudflow 10 year.mxd Plot Date: 4/10/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P34I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST "Smuggler Mine On-Site Pond"Landscape Pond 811083008290828082708310826082508240823082208210 82008190818081708160797081508140798078908130803081207990804081008090 801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 84208010797080507870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 79107980786081207940 84507890 793079507840789078907 8 4 0 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 786086607930 7 9 0 0 788078507900 814084307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 50-Year Event Smuggler/Hunter Surface Drainage Master Plan ES.5 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-08 Mudflow 50 year.mxd Plot Date: 4/10/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P35I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGST "Smuggler Mine On-Site Pond"Landscape Pond 8110830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 7900 8 0 9 0 84207870 79607840 865079307 8 9 0 787083907930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 837083207960 7870 7940 7930 7980795079207860 7 8 4 0 786086607930 7 9 0 0 788078507900 84307910 8 0 7 0 7880790079507900 7900 7910 7960793078607910 7890 0 300 Feet o Maximum Mudflow Depth 100-Year Event Smuggler/Hunter Surface Drainage Master Plan ES.6 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-09 Mudflow 100 year.mxd Plot Date: 4/10/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P36I. " 777 Spruce St. " Oak Lane"633 Spruce Street Roari ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGST "Smuggler Mine On-Site Pond"Landscape Pond 811083008290828082708310826082508240823082208210 82008190818081708160797081508140798078908130803081207990804081008090 8010808080708020800079208050791079607900795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 84208010797080507870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 79107980786081207940 84507890 793079507840789078907 8 4 0 7920 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 786086607930 7 9 0 0 788078507900 814084307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Mudflow Hazard Yellow Zones Smuggler/Hunter Surface Drainage Master Plan ES.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01Revised90pctSubmittal\Fig3-10MudflowYellowZones.mxdPlotDate:4/10/2015Legend Buildings Yellow Mudflow Zones General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P37I. P38I. April 2015 ES-xiii | List of Acronyms and Abbreviations ALTERNATIVE DEVELOPMENT To manage stormwater runoff in the study area, alternatives for flood control were developed conceptually so that feasibility and cost of flood control projects could be estimated and compared. Generally, two basic strategies to mitigate flood hazards and improve water quality aspects were investigated for each basin: 1) sub-regional detention and, 2) conveyance improvements that include storm sewer improvements. Basic flood control concepts considered for each basin are listed in Table ES.1. The Conveyance alternative consists of releasing all stormwater runoff without any new detention. This alternative would require that culverts and storm sewer outfalls in the study reaches be sized to convey the estimated peak flows. Detention can be used to reduce stormwater flows from upstream areas in the watersheds, and the Detention alternative examines this scenario for potential detention sites in each watershed (if possible) where existing downstream infrastructure does not have adequate capacity or to minimize proposed storm system costs downstream. Table ES.1 Basic Flood Control Alternatives Major Basin 5-year Detention 10-year Detention 5-year Conveyance 10-year Conveyance Hunter Creek Basin X Gibson Avenue Basin X X Neale Avenue & OK Flats Basin X X Riverside McSkimming Basin X X Eastwood Basin X Stillwater Bridge Basin X In addition to the two design approaches, two additional scenarios were considered when developing each alternative for each major basin: 1) the “With Easements” scenario that minimizes storm sewer system costs by using the shortest feasible route and obtaining easements to cross private lands and, 2) the “Minimal or Without Easements” scenario, which uses longer storm sewer routes to minimize or eliminate private easements for each alternative to reduce cost due to the expensive cost of land in the study area. The objective of this alternatives evaluation was to identify cost effective measures to control stormwater runoff from the study area watersheds such that: 1) runoff can be conveyed safely within existing and proposed infrastructure, 2) the potential for damages to conveyances and buildings within each watershed from the design flood is reduced, and 3) flood control measures can be implemented effectively as development occurs and funding becomes available. After a feasible alternative was identified, it was conceptually designed according to established project criteria and modeled using InfoSWMM and other hydraulic software to confirm performance. After hydraulic modeling confirmed performance, conceptual-level cost estimates were prepared to assess and compare the cost effectiveness of each feasible alternative. This evaluation P39 I. ES-xiv | Executive Summary April 2015 includes a listing of structural and conveyance improvements with the estimated total cost for each, and considering the benefits for each alternative. The costs account for property acquisition required for locating detention facilities and pipe alignments as well as estimating costs to design and construct the project. Other continuing costs, such as operation and maintenance, were not considered. The costs for the recommended alternatives in each basin are summarized in Table ES.2. Table ES.2 Proposed Project Costs by Watershed Proposed Projects by Major Basin Land Cost (x$1,000) Construction Cost (x$1,000) Total Cost (x$1,000) Hunter Creek Basin (10-year Conveyance) $54 $132 $186 Combined Gibson Avenue and Neale Avenue & OK Flats Basins (10-year Conveyance) $494 $1,114 $1,608 Riverside McSkimming Basin (10-year Conveyance with Limited Easements) $150 $782 $932 Combined Eastwood and Stillwater Bridge Basins (10-year Conveyance with No Easements) $0 $1,212 $1,212 Total Cost of Proposed Projects $698 $3,240 $3,938 MASTER PLAN The selected alternatives for each basin were further evaluated based on cost and its effectiveness in meeting project objectives using a ranking spreadsheet. Several criteria and weighting percentages were selected to prepare the preliminary ranking of the suggested projects, and the project ranking scores were calculated. A stormwater infrastructure improvement plan, which would be implemented over a period of 10 years, is in Table ES.3. The proposed phasing is driven by project rank, sequence with related projects, and by financing and cost sharing opportunities with Pitkin County, CDOT, or other entities. Phasing is shown over only 10 years due to the relative average cost of the projects related to Aspen’s existing budget priorities. The plan should be revisited every year as part of Aspen’s budgeting process. As some of the projects include significant improvements outside Aspen’s jurisdiction, the improvement plan separates costs and includes additional proposed funding sources. As part of master planning for urbanizing watersheds, it is generally recommended that Aspen implement the following: • Provide regular maintenance of existing dry wells in the study area by cleaning out any accumulated silt that affects the infiltration rate of collected stormwater in each well. • Provide regular maintenance to existing and proposed storm sewer networks to ensure the conveyance capacity is not hindered during a major precipitation event. P40 I. April 2015 ES-xv | List of Acronyms and Abbreviations  Provide designated snow storage areas that do not block any storm sewer systems, and that would not drain to private property.  Continue implementing water quality treatment as much as practicable throughout Aspen in accordance with the standards in Chapter 8 of the URMP.  Coordinate with Pitkin County and the Smuggler Mine to ensure that Smuggler Mountain Road is maintained with positive drainage to the existing cross culverts.  Many basins in this Master Plan have significant area within Pitkin County’s jurisdiction. Alternatives were proposed for those areas, but were not included in the conceptual design, per Aspen’s direction. Coordinate future improvement projects with Pitkin County to leverage funding and increase functionality by including the upstream areas.  Coordinate with existing and future land owners to align these proposed improvements with future development such as the private property within the Hunter Creek basin where proposed improvements will be tied to the single affected land parcel and will be the obligation of the land owner. This report covers the plan in detail, culminating with conceptual design plan and profiles sheets in Appendix G. The plan described on these sheets is presented at a “conceptual” design level. The final design of the Master Plan allows great flexibility to incorporate alternative concepts as long as they maintain the hydraulic function described in this report. P41 I. ES-xvi | Executive Summary April 2015 This page intentionally left blank P42 I. April 2015 ES-xvii | List of Acronyms and Abbreviations Table ES.3 Stormwater Capital Improvements Phasing 2016-2026 Proposed Stormwater Projects Basin Total Project Cost (x$1,000) Aspen Capital Costs Rank (1 to 11) Proposed Phasing (x$1,000) Potential Funding Sources Land Cost (x$1,000) Construction Cost (x$1,000) Total Cost (x$1,000) 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 Gibson Avenue Main Stem, N17 Branch, & G09 Branch Combined Gibson Avenue and Neale Avenue and OK Flats Basins $540 $0 $432 $432 1 $58 $374 County cost-sharing E. Hopkins Outfall North Branch Riverside McSkimming Basin $187 $0 $187 $187 2 $187 County cost-sharing Stillwater Bridge Basin Main Stem Combined Eastwood and Stillwater Bridge Basins $576 $0 $0 $0 2 Coordinate with Pitkin County to add to County's CIP. County Project Stillwater Bridge Basin South Branch Combined Eastwood and Stillwater Bridge Basins $377 $0 $0 $0 3 Coordinate with Pitkin County to add to County's CIP. County Project Williams Woods Proposed System Hunter Creek Basin $186 $0 $0 $0 4 Add information to permitting file for property to ensure inclusion in future development. By development Oklahoma Flats Outfall Neale Avenue Basin $54 $0 $54 $54 6 $54 E. Hopkins Outfall South Branch Riverside McSkimming Basin $199 $0 $73 $73 6 $73 Eastwood Main System Eastwood Basin $258 $0 $121 $121 7 $121 County cost-sharing, CDOT cost sharing along Highway 82 Neale Avenue Storm System Neale Avenue Basin $123 $0 $123 $123 8 $123 E. Cooper Avenue Outfall, Mildland and Cooper Branch, & McSkimming Branch Riverside McSkimming Basin $546 $150 $396 $546 9 $53 $493 County cost-sharing Lone Pine Rd. Outfall Gibson Avenue Basin $169 $0 $169 $169 10 $169 King Street Branch Neale Avenue Basin $43 $0 $43 $43 10 $43 River Bluff Townhomes Branch Gibson Avenue Basin $147 $112 $34 $147 11 $147 Brown Ln. Branch and N12 Branch Combined Gibson Avenue and Neale Avenue and OK Flats Basins $533 $381 $152 $533 12 $20 $513 TOTAL $3,938 $644 $1,783 $2,427 $54 $78 $513 $374 $260 $121 $166 $53 $493 $169 $147 P43I. P44 I. SECTION ONE INTRODUCTION April 2015 1-1 | Introduction 1 Section 1 ONE Introduction 1.1 AUTHORIZATION This Surface Drainage Master Plan (Master Plan) documents a planning study authorized by the City of Aspen, Colorado, in an agreement with URS Corporation (URS) dated June 4, 2012. The study area, shown in Figure 1.1, lies to the east of the Roaring Fork River and includes watershed area on Smuggler Mountain to the southeast of Hunter Creek. The study area encompasses portions of the City of Aspen (Aspen) and unincorporated Pitkin County. The sponsoring agency of this study is Aspen. Project stakeholders include: Aspen, Pitkin County, the Salvation Ditch Company, Smuggler Mine Company, and the citizens of Aspen. 1.2 PURPOSE & SCOPE The objective of this project is to perform hydrologic, hydraulic, and mudflow evaluations of the area shown on Figure 1.1 to document the existing storm drainage patterns, structures, and facilities throughout the Smuggler/Hunter area of Aspen. The results of these analyses will be used to prepare a new Master Plan that will provide recommendations for future improvements, conceptual designs, and cost estimates that address water quantity, water quality, and mudflow issues. The primary tasks of this project are to: • Inventory the existing stormwater infrastructure and update the existing geographical information system (GIS) data • Develop and execute hydrologic and hydraulic models • Identify problem areas • Identify potential locations for stormwater quality facilities • Evaluate potential debris and mudflow areas • Identify mine water outflows and evaluate their impacts on the stormwater conveyance system • Evaluate and document the capacity of irrigation ditches and facilities • Recommend capital improvement projects, provide conceptual designs and a capital plan to reduce or eliminate drainage and flooding problems with available resources • Develop a Master Plan focused on conveyance and water quality improvements, as well as addressing mudflow potential P45 I. 1-2 | Introduction April 2015 P46I. April 2015 1-3 | Introduction 1.3 MAPPING AND SURVEYS Through the Aspen/Pitkin County GIS Department, Aspen provided three aerial images and three topographic datasets in GIS format for use on this project. The aerial images were captured in 2008 and 2010 by MapCON. The 10-foot contours were derived from aerial imagery captured in 2003 by Sanborn, Inc. The 1- and 2-foot contours were derived from the 2008 aerial flyover. The hydrologic and hydraulic analyses performed in this study are based on all of the contour datasets, as they are generally limited in extent, along with U.S. Geological Survey (USGS) mapping for the northeastern (headwaters) portions of some watersheds. Several other reference datasets were provided by the Aspen/Pitkin County GIS Department for use on the study as needed, including: • Aspen Zoning • Curb and Gutter • Ditch • Drives • Edge of Pavement • Flood Hazard Area • Forest • Open Space • Open Space Easements • Parcels • Parks • Pitkin Zoning • Roads • Soils • StormWater_Line • StormWater_Point • Structures • Towns • Vegetation • Water While Aspen provided the StormWater_Point and StormWater_Line datasets, additional information on the storm drainage system was needed, specifically pipe sizes and inverts. Drainage infrastructure including inlets, storm sewers, culverts, dry wells, and manholes, was surveyed for the hydrologic and hydraulic analysis. Aspen’s GIS database was updated to include the new survey information. The surveyed data will replace the older GIS data for the Smuggler/Hunter area within Aspen’s database. Available record drawings and drainage reports were obtained from Aspen in portable document format (PDF). Site visits were also conducted by the URS Team in July and October 2012 throughout the Smuggler/Hunter area, and photographs were taken to document existing drainage structures, vegetative cover, development status, mine flow locations, historic land/mud slide locations, and other features. Photographs taken during the site visits are presented in Appendix A. 1.4 ANALYSIS AND DESIGN CRITERIA Analyses for this Master Plan were performed in accordance with the criteria and guidelines set forth in the following documents: • City of Aspen. Urban Runoff Management Plan (URMP), Revised September 2014. (Reference 1) P47 I. 1-4 | Introduction April 2015 • City of Aspen Engineering Department. City of Aspen, Colorado, Design Standards, June 2005. (Reference 9) • Urban Drainage and Flood Control District (UDFCD). Urban Stormwater Drainage Criteria Manual (UDSCM), Revised April 2008. (References 55 and 56) 1.5 ACKNOWLEDGMENTS The URS Team wishes to acknowledge the individuals who assisted in the development of this Master Plan. • April Long, PE, Stormwater Manager • Trish Aragon, PE, City Engineer • Josh Rice, PE, Development Engineer • Bridgette Kelly, GIS Specialist The following URS Team personnel were responsible for development and completion of this Master Plan: • Principal-in-Charge: Kevin Klimek, PE • Project Manager: Kimberley Pirri, PE, CFM • Hydrologic/Civil Engineer: Max Shih, PhD, PE • Hydraulic/Civil Engineer: Joey Machala, PE • GIS Specialist: Jim Crawford, GISP • Environmental Scientist: Eric Petterson (RMES) • Surveyor: Sam Phelps, PLS (SurvCO) P48 I. SECTION TWO STORMWATER RUNOFF AND DRAINAGE FACILITY CAPACITY ANALYSIS April 2015 2-1 | Stormwater Runoff and Drainage Facility Capacity Analysis 2 Section 2 TWO Stormwat er Runoff and D rainage Facilit y C apacit y Analysis 2.1 INTRODUCTION This section describes the analysis of rainfall-runoff and stormwater conveyance within the Study Area for several storm event frequencies and the capacity of the existing stormwater infrastructure to convey flows for those events to Hunter Creek and the Roaring Fork River. Also described are the impacts and analysis of mine flows and irrigation and as well as a qualitative assessment of the water quality (wetlands and riparian) areas within the Study Area. 2.2 STUDY AREA Aspen lies within Pitkin County in Township 10 South, Range 85 West of the 6th Principal Meridian. The selected study area (Study Area) within the corporate limits of Aspen mainly lies in the valley and east bench of the Roaring Fork River that runs from the southeast to the northwest along the base of the south side of Smuggler Mountain. The Study Area is roughly bounded by Hunter Creek on the north, the Roaring Fork River to the west, the upland areas of Smuggler Mountain to the east, and by the southern boundary of the Stillwater Bridge Basin drainage area. The total study area is approximately 0.5 square mile with elevations ranging from approximately 7,830 feet to 10,460 feet. Surface runoff from the majority of the Study Area flows through the developed areas of Aspen on Smuggler Mountain before emptying into the Roaring Fork River. A small portion of the Study Area contributes flow to Hunter Creek, which then empties into the Roaring Fork River. The Roaring Fork River ultimately flows into the Colorado River at the City of Glenwood Springs. The major drainage basins and Study Area are shown on Figure 2.1. 2.3 MINE FLOWS AND IRRIGATION With the presence of the Smuggler Mine, several historic mining shafts, and several irrigation ditches in the Study Area; there is potential that stormwater flows and drainage patterns may be impacted by these facilities. The Smuggler Mine permit area occupies 9.7 acres of a 29.7 acre parcel on Smuggler Mountain above the Study Area. The Smuggler Mine is a historic, underground mine that has been in operation for approximately 133 years. The mine’s current operation is limited to a threshold tonnage because it is a tourist mine. The Smuggler Mountain Superfund Site was created to address excess levels of lead and zinc in the soil where mine spoils had been stored. Aspen ordinance and permitting procedures address soil excavation and removal in these areas. While the Aspen Water Department monitors flow rate and depth in several ditches, including mine flow locations, they do not monitor water quality as it is not required by the State of Colorado. Therefore, the water quality of the mine flows is unknown. The nearest publically available water-quality data is downstream at the USGS gaging station Roaring Fork River near Aspen, CO. (No. 09073400); which due to its location downstream, cannot be used to evaluate the mine’s runoff water quality. P49 I. 2-2 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 This page intentionally left blank P50 I. !!!!!!! !!!!!!!!!!!!!! !! ^_ ^_ ^_ %O %O %O %O %O %ORoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENASTStillwater Bridge Basin Eastwood Basin Riverside McSkimming Basin Neale Avenue and OK Flats Basin Hunter Creek Basin Gibson Avenue Basin"Hunter Creek Basin N. Spring St. Aspen Art Museum Park Snyder Park Herron Park Gibson Ave. Garrison Park Johnson Shaft Unknown Source Mollie Gibson Shaft 8100 90009100920093009 4 0 0 95009600970098008000 10300104007900 102001 0 1 0 010000 87 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001030010200820086008100 8900 8300 9 9 0 0 90008600890080001 0 3 0 0 101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010000840080008000870080008500 9500850088000 1,000 Feet o Major Drainage Area Map Smuggler/Hunter Surface Drainage Master Plan 2.1 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-01 Major Drainage Basinsr90.mxd Plot Date: 1/9/2015 Legend ^_Mine Flow Sources %O Potential Water Quality Locations !!Irrigation Ditch, Culvert Irrigation Ditch, Open Topographic Contour (feet NGVD29) Study Area Boundary Wetland Areas Riparian Areas Surface Water Major Basins Eastwood Basin Gibson Avenue Basin Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Stillwater Bridge Basin P51I. P52I. 2-4 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 During the site investigation for mine and irrigation flows on October 8, 2012, groundwater flows were observed to be coming from three locations that were corroborated as mine flows by Aspen staff. The three sites are described in Table 2.1 and shown in Figure 2.1. Table 2.1 Mine Shaft Locations Number Mine Flow Name Visual Estimate of Flow Rate1 (gpm) 1 Johnson Shaft No flow 2 Mollie Gibson Shaft 30 3 Unknown Source (may not be directly connected to the mine) 10 Notes: 1Observed October 8, 2012. gpm = gallons per minute Five ditches flow through the Study Area. These ditches were investigated in the field and through the use of the Colorado Decision Support System (CDSS) (Reference 14) database online. While the CDSS reported more than a dozen diversion structures in and above the Study Area, only five have significance for stormwater. The five ditches are described in Table 2.2 and are shown in Figure 2.1. Table 2.2 Irrigation Diversions/Ditches Diversion Structure Name1 CDSS Structure ID1 Owner(s)1 Decreed Rate Total (cfs)1 Average Flow2 (cfs) Source3 Latitude1 Longitude1 Mollie Gibson 2 Shaft D (flows into Astor Ditch)4 877 Ernest Kapelli 3.5 0.3 Mine Flow 39.190691 -106.809678 Astor Ditch 1234 Peter Wirth; Jeffery Shoaf 0.122 Not Available Mine Flow 39.189443 -106.811082 Mocklin Ditch (Also known as the Cowenhouven Ditch) 1333 None Listed 0.4 0.6 Mine Flow 39.194120 -106.813981 Salvation Ditch 981 Salvation Ditch Company 59 Not Available River Diversion 39.180601 -106.802566 Riverside Ditch 963 Jim Snyder 6 1 River Diversion 39.174909 -106.810801 Notes: 1From CDSS records; 2From City of Aspen Water Department records, 3From City of Aspen Stormwater staff, 4Mollie Gibson 2 Shaft D is shown as part of the Aster Ditch in Figure 2.1; CDSS = Colorado Decision Support System; cfs = cubic feet per second; ID = identification Irrigation ditches are typically designed along flat slopes and with only the capacity needed to convey the decreed flow for the ditch. There is generally no capacity available to accept stormwater flows; nor would such carrying capacity be guaranteed, as most ditches are privately owned. Therefore, irrigation ditches were ignored for the purposes of the stormwater rainfall- runoff analysis in this study. This is consistent with the Colorado Water Conservation Board’s (Reference 13) stormwater management policy, as well as UDFCD’s (Reference 55) drainage policies. It is also consistent with the Drainage Facility Capacity Analysis WRC prepared in P53 I. April 2015 2-5 | Stormwater Runoff and Drainage Facility Capacity Analysis 1998 (Reference 63) as the initial report for the Aspen Surface Drainage Master Plan (Reference 64), which ignored the diversion of the Summer Ditch. 2.4 WATER QUALITY AREA ASSESSMENT As part of the drainage capacity analysis, the URS team conducted field assessments of wetlands and riparian areas and of potential water quality pond locations within the Smuggler/Hunter study area. Understanding location and the existence of wetland and riparian areas is critical to stormwater planning to account for the natural water quality treatment associated with such areas as well as to avoid adversely impacting the areas with future planned facilities. Further, understanding where future water quality facilities may be planned on publically-owned lands is a first step to being able to viably include such facilities in a Master Plan, especially in a locale such as Aspen, where land values are at a premium. Identified wetlands and riparian areas and water quality pond locations were delineated in GIS and are shown on Figure 2.1. Photos of the wetlands and riparian areas investigation are included in Appendix A. Wetlands are defined by the USACE as areas having positive evidence of three environmental parameters: hydrophytic vegetation, hydric soils, and wetland hydrology. Hydrophytic vegetation includes any vascular plant that grows in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content. Hydric Soils include those soils saturated, flooded, or ponded for a sufficient duration during the growing season to exhibit anaerobic indicators in the upper 12 inches. Wetland Hydrology encompasses all hydrologic characteristics of areas inundated or saturated to the surface for at least 5 percent of the growing season in consecutive days. Riparian areas are considered to be those moderately moist, grassland or woody habitats located adjacent to wetlands that form a transition between the wetland and upland areas. The riverside areas with any existing wetland areas are located on the uppermost reaches of the Roaring Fork River and then the lowermost reaches within the study area, including parts of Hunter Creek. The upstream areas occur on the Roaring Fork River beginning upstream of the Highway 82 bridge that crosses the river at Riverside Drive and continue downstream to just above the headgate for the Riverside Ditch, which is located upstream of the Aspen Club. Downstream, the only significant wetlands occur below the John Denver Sanctuary, with the most obvious site being the ponded area near the Aspen Art Museum. While there are some stretches in Aspen with a thin area of healthy riparian shrubs (for example, along the Glidden Bridge on Neale Avenue), many others are essentially “armored” or all understory and/or overstory riparian/wetland vegetation has been removed. Hunter Creek has a fairly extensive native area near where the Salvation Ditch crosses, where there is a riparian community that may have some wetlands associated with the drainage. There is a another site west of Red Mountain Road, along Hunter Creek, which is equally close to the Roaring Fork River and where Shady Lane wraps around it, that is a sunken native area with riparian vegetation. This site may also have wetlands and is just upstream of the confluence of Hunter Creek and the Roaring Fork River, yet appears isolated. There are “fringe” wetlands along the Roaring Fork in this area as well, essentially across the river from the Jenny Adair site beginning at the Mill Street Bridge and easily visible from the pedestrian trail. P54 I. 2-6 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 The field assessment of potential water quality pond locations was conducted with Aspen staff on July 23, 2012. Six potential sites for the possible location of future water quality facilities were identified. Four of these sites are in established city-owned parks: Aspen Art Museum Park, Herron Park, Garrison Park, and Snyder Park. The fifth site is located in a “pocket park” at the south end of North Spring Street, near the Roaring Fork River. The sixth site is located along the roadway right-of-way, east of the intersection of Gibson Avenue and Red Mountain Road. The wetland and riparian areas, along with the potential water quality sites, will be considered when recommended improvements are evaluated later in this Master Plan. 2.5 HYDROLOGY Per Chapter 3 of Aspen’s URMP (Reference 1), the Rational Method, Colorado Urban Hydrograph Procedure (CUHP), and EPA’s Storm Water Management Model (SWMM) are recommended for watershed hydrologic modeling and runoff estimation. The Rational Method is a simplified hydrologic method only developed for peak flow prediction in basins less than 90 acres. It is not applicable for the larger basins and estimating runoff volumes for this study. The CUHP 2005 software, version 1.4.4, developed by UDFCD (Reference 54) has the capacity to simulate basin hydrographs and peak discharges for a large watershed and was used for this study. CUHP 2005 can also estimate the hydrographs for small drainage areas, with computational results comparable to the Rational Method. In this study, runoff hydrographs were estimated using CUHP 2005 with UDFCD’s recommended methodology for estimating rainfall infiltration losses, which is Horton’s Method. EPA’s SWMM software version 5 (EPA SWMM 5.0) (Reference 51) is a computer program that is used to generate surface runoff hydrographs from sub-catchments and then route and combine these hydrographs. In this study, as runoff hydrographs were generated using CUHP 2005, only the software’s ability to combine and route hydrographs was used. The CUHP runoff hydrographs were routed using InfoSWMM (Reference 22), a highly-developed, well-supported hydrologic/hydraulic modeling software that implements the EPA SWMM analysis methods in a fully GIS -integrated environment and produces models and output compatible with EPA SWMM 5.0. For stormwater planning studies using SWMM, the kinematic wave approach for routing flows is generally recommended for use because it is a stable computational method that produces consistent results across typical storm drainage systems without excessive input requirements. It is the recommended method described in the UDSCM. Model components and selected methodologies are listed in Table 2.3 Table 2.3 Model Components Model Component Selected Methodology Infiltration Loss Horton’s Method Runoff Transformation Colorado Urban Hydrograph Procedure Channel Routing Kinematic Wave Descriptions of the hydrologic analysis methodology, data inputs, model setup, and modeling results are presented in this section. P55 I. April 2015 2-7 | Stormwater Runoff and Drainage Facility Capacity Analysis 2.5.1 CUHP Analysis The CUHP 2005 software, version 1.4.4 was used for computing the storm runoff hydrograph for each study drainage basin. The CUHP is a deterministic hydrologic procedure that calculates rainfall losses due to soil infiltration, evaporation, and ground cover, and estimates runoff hydrographs at the outfall of a drainage basin, based on a given rainfall distribution. Primary inputs include rainfall depths, basin geometry characteristics, soil infiltration parameters, and surface imperviousness. The hydrologic parameters determined for the existing conditions, and the proposed conditions of drainage improvements were used as inputs in the CUHP 2005 models to compute the basin runoff hydrographs. Within the Study Area, six major drainage basins were analyzed. Sub-basin characteristics required for CUHP are drainage area, watercourse length and centroid length, drainageway slope, percent imperviousness, soil infiltration rates, Horton’s decay coefficients, and time of concentration (tc). Sub-basin geometry, slopes, and lengths were measured from the best available data of 1-foot, 2-foot, and 10-foot contours, where available, and the 7.5-minute USGS quadrangle maps in the upper elevations of the project area. Details on the estimation process and assumptions associated with each sub-basin’s characteristics are discussed in the subsequent sections. A summary of the CUHP input parameters used for each sub-basin is included in Appendix B. 2.5.1.1 Design Rainfall One-hour duration precipitation values were adopted for the 2-, 5-, 10-, 25-, 50-, and 100-year return periods from Chapter 2 of Aspen’s URMP (Reference 1), which reflect the revised rainfall values published in NOAA Atlas 14, Volume 8 in 2013 (Reference 30). These 1-hour rainfall depths are distributed to a 2-hour precipitation hyetograph within CUHP. Design rainfall depths used in the hydrologic analysis for the project are listed in Table 2.4. The 2-hour rainfall distributions are shown in Figure 2.2. Table 2.4 Aspen, Colorado Design Rainfall Depths Return Period (Year) 1-Hour Precipitation Depth (inch) 2 0.47 5 0.64 10 0.77 25 0.95 50 1.09 100 1.23 P56 I. 2-8 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 Figure 2.2 CUHP Frequency Storm Rainfall Depth Distribution for Aspen, Colorado 2.5.1.2 Sub-basin Delineations Sub-basins for the CUHP analysis were delineated in an ArcMap® GIS environment based on drainage divides estimated from the 1-, 2-, and 10-foot contour topography (2008) provided by Aspen, and USGS 7.5-minute quadrangles for the upper areas of the major basins. Sub-basins were further delineated based on the expected control of runoff by swales, structures, roadway fills and cuts, and major drainage features such as storm sewers. The sub-basin boundaries and stream network were refined using aerial photography, field survey (2012), and site visit data. The Study Area of six major drainageway basins was divided into a total of 82 sub-basins. Sub- basins in headwater areas, where land use and soils were generally homogeneous, were not divided, with the largest area being 329 acres. Basin maps are provided on Figure 2.3. 2.5.1.3 Sub-basin Slope CUHP requires input of watershed slope for each sub-basin. The full length of the flow path is divided into separate reaches of uniform slope; then those slopes are averaged based on incremental length to produce the length-weighted average that is input into CUHP. CUHP also specifies that the maximum weighted slope cannot exceed six percent. Where slopes exceed six percent; the weighted slope was adjusted using the slope correction process outlined in the CUHP manual. 2.5.1.4 Soils and Geology Soils data in the study area dictates the fraction of precipitation that ultimately becomes runoff. As Aspen’s soil map provided in the URMP did not provide full coverage of the study area, the Soil Survey Geographic (SSURGO) database for Pitkin County was obtained from the U.S. Department of Agriculture’s Geospatial Data Gateway website and used to delineate the areas of soil groups within the study watersheds. Detailed SSURGO soil survey data circa 2008 were used throughout the study area but supplemented with general SSURGO soil survey data in the 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0:00 0:28 0:57 1:26 1:55Rainfall Depth (inch) Time (hr:min) 2-year 5-year 10-year 25-year 50-year 100-year P57 I. April 2015 2-9 | Stormwater Runoff and Drainage Facility Capacity Analysis upper reaches where there was no detailed coverage. The compiled soil map for the Study Area is shown on Figure 2.4. The soil parameters required by CUHP are initial infiltration rate, final infiltration rate, and Horton’s decay coefficient. Hydrologic soil groups were used to identify the soil parameters. According to the URMP and USDCM Volume 1 (References 1 and 55), the values in Table 2.5 are recommended for CUHP. When a watershed has several different types of soils, the representative infiltration rate is estimated as the area-weighted average value. Initial and final (or fully saturated soil) infiltration rates are presented in Table 2.5 because infiltration occurs along a decay function, with more infiltration at the beginning of a rainfall event and less infiltration as the soil becomes saturated. The computed area-weighted soil infiltration rates and decay coefficients for each sub-basin are included in the CUHP parameters in Appendix B, along with the supporting digital GIS files. Table 2.5 Recommended Horton’s Infiltration Rates for Different Soil Groups (UDFCD 2001) NRCS Hydrologic Soil Group Initial Infiltration Rate (inch/hr) Final Infiltration Rate (inch/hr) Decay Coefficient A 5.0 1.0 0.0007 B 4.5 0.6 0.0018 C 3.0 0.5 0.0018 D 3.0 0.5 0.0018 C/D 3.0 0.5 0.0018 Water 0.0 0.0 0.0018 Notes: inch/hr = inches per hour; NRCS = National Resources Conservation Service Figure 2.5 shows the estimated initial, area-weighted soil infiltration rates for all major basins, as estimated using the values for each soil group shown in Table 2.5 and indicates the Study Area has a relatively high infiltration rate with low runoff characteristics. 2.5.1.5 Land Use and Surface Imperviousness Watersheds are composed of pervious or impervious areas. As urbanization occurs, the amount of impervious areas increase, decreasing the amount of precipitation that infiltrates and increasing the amount that runs off. The overall imperviousness of the drainage basin is calculated by dividing the impervious area in the drainage basin by the total area of the drainage basin. Land use data were applied to develop the hydrologic parameters required by CUHP. A land use map, Figure 2.6, was prepared by delineating the impervious percentages based on Aspen zoning, Pitkin County zoning, designated open space, and parcel data, as well as site visits and aerial photography (2008) provided by Aspen. The imperviousness parameters for each sub- basin were estimated as composite values resulting from a weighted-area average computation using the recommended parameter values. Based on discussions with Aspen, the watersheds are built-out and will mostly experience in-fill development in the future; therefore, no land use characteristics for future build-out conditions were estimated. P58 I. !!!!!!!!!!!!!! !!!! !!!! ! ! %O %O HunterCreek RoaringForkRiver H04 Gibson Ave. Aspen Art Museum Park 7 9 7 0 7880 7950 7960 787079407860793078907910 7 9 2 079007850 7980 7990800080108020784080308040783079307 8 3 0 78507980 79007890 78907860 79407940 7 8 5 0 7900 79507880786079107 8 8 0 7840 7930 7 8 3 0 7840 78307840784079007960 7 8 4 0 78707910 797078907890 8 0 3 0 7 8 9 0 79507970793079307880 7 9 2 0 7 8 4 07890 7 9 1 07840 7940 7940 7880 78907 9 2 0 7920 78407 9 3 0 79007 9 3 0 7960SalvationM o c k l i n M o c k l i n Mocklin M o ck lin Hunter Creek BasinHunter Creek Basin H03 H05 H02 H04 H01 OFALL-13 OFALL-12 OFALL-11 H02 H05 H03 H01 REDMTNRDSPRUCESTLONEPINERD VINESTGIBSONAVE TEALCTNMILLSTSPRUCECTWILLIAMS WAY RACESTBROWNLNS H A D Y L N PUPPYSMI THSTNSPRI NGSTCOWENHOVENCTWALNUT STINDEPENDENCEPL BRENDENCT0 200 Feet o Drainage Basins and SWMM Routing Elements Hunter Creek Basin Page 1 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 1 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Divider Outfall Conduit Overflow Legend %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water P59I. !!!!!!!!!!!!!! !!!! !!!! ! ! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!UT %O %O G03J06-G10 J05-G10 J04-G10 J03-G08 J02-G08 J01-G05 J03-G06 J02-G03 J01-G06 P01-G03 DW07-G03 DW05-G03 DW04-G03 DW02-G04 DW01-G04 DW06-G03 DW08-G03 DW03-G03 OFALL-2 OFALL-5 OFALL-4 OFALL-3 OFALL-1 OFALL-DW OFALL-P01-G03 G08 G13 G11 G09 G12 G10 G05 G07 G06 G04 G02 G01 D10-G10 D09-G10 D08-G08 D08-G10 D07-G09 D06-G02 D05-G02 D03-G02 D02-G02 SPRUCE ST PARKCIRLONEPINERD NSPRI NGSTVINESTRACESTTEALCTAJAXAVEBROWNLNNICHOLASLNSPRUCECTWILLIAMSWAYWALNUTST WILLIAMSRANCHDRS OU T H AVE FREESILVERCTCOWENHOVENCTINDEPENDENCEPLRoar i ngFor kRi ver Gibson Ave. Aspen Art Museum Park 7880 7890798079707990 8000801079407950 796079007 9 2 07910 7930787080207860803080408050806080708080 7850809081007840811081208130814081508160817081808190789080207960 7 8 7 0 7 8 9 0 79307860 7 8 7 0 796078707890 7890 78507880 7870 78707860 7 9 1 0 7940 78707910 7 8 4 0 7 8 4 0 79607880 8030789079 1 0 809080407890 7880 7900 79407 8 8 0 7940 7 9 3 07910 793079507900 79307860 79407930 79507 9 2 0 78607850Gibson Avenue Basin SalvationMocklin M o c k l i n Mocklin G05 G08 G13 G06 G04 G07 G09 G01 G02 G11 G10 G03 Hunter Creek G12 0 200 Feet o Drainage Basins and SWMM Routing Elements Gibson Avenue Basin Page 2 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 2 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Storages Dry Well UT Underground Storage Conduit Overflow Orifices Outlet Weirs Legend %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water!!!!!!!!!!! ! ! ! ! ! ! ! !!!!!!!!!!!UT G03 J03-G06 J02-G03 J01-G06 G04 G02 G01D06-G02 D05-G02 D03-G02 D02-G02 OFALL-DW OFALL-P01-G03 P01-G03 DW07-G03 DW06-G03 DW05-G03 DW04-G03 DW03-G03 DW02-G04 DW01-G04 DW08-G03798080007990 801079708020 80308040 7960 8 0 1 0 80108010Salvation G05 G04 G02 G03 G01 SILVERLODEDR TEALCTWILLIAMSRANCHDRP60I. !!!!!!!!!!!!!! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! ! ! ! !!!?> UT ^_ ^_ ^_ %O %O %O %O SOUTH AV E N16 N25 N22 N26 N11 N01 N06 N03 J20-12 J24-N17 J23-N24 J22-N23 J19-N12 J16-N13 J15-N10 J14-N12 J13-N12 J12-N12 J11-N10 J10-N10 J09-N10 J08-N10 J07-N05 J06-N10 J04-N05 J03-N09 J21-N23 J18-N17 J17-N17 RoaringForkRiver GIBSONAVE PARKCIREHYMANAVE EHOPKINSAVE SMUGGLERMTNRDSPRUCESTSILVERLODEDROAKLNLONEPINERD PARKAVENSPRINGSTNEALEAVE VINEST SSPRINGSTEMAINST KINGSTMAPLELNRACEST SORIGINALSTTEALCTAJAXAVEMIDLANDAVENI CHOLASLNQUEEN STWALNUTST COTTONWOODLNRIOGRANDEPL WILLIAMSRANCHDRSWESTENDSTECOOPERAVE WILLIAMSWAYARDMOREDRMASCOTTE LN CLEVELANDSTBAYST FREESI LVERCTCOWENHOVENCTEFRANCISST EBLEEKERST MATCHLESSDRHAROLDROSSCTREGENTSTBRENDENCT EHOPKINSAVENSPRINGSTP03-N16 P02-N01 DW01-N10 DW02-N04 N14 N24 N23 N21 N20 N19 N18 N15 N17 N12 N13 N07 N02 N10 N08 N05 N09 D2-N12 D13-N23 D11-N21 D10-N21 D09-N21 D08-N21 D07-N21 D06-N26 D05-N21 D04-N20 D03-N19 D01-N02 D01-N06 N04 D12-N23 Johnson Shaft Unknown Source Mollie Gibson Shaft Gibson Ave. Herron Park Garrison Park N. Spring St.798081108000797079908010802080408030805080608070 832083108080830080908100829083308280827081208260825082408130814079608150816081708230818082008190822082108340835079508360837079408380 7 9 3 0 8390840084108420843084407920 845084608470848084908500851085207910 7900 853078908540 8550 85608570858085907880 7870 8 6 0 0 861078608620 8630864086508670 86608680 86908700 78508710 8070 8610 79607 8 8 0 869080607920 7 9 3 0 7960 8120 7850 87008660 7950 7 9 3 0 7880791079507970 8600 7910 79707880 80507 9 2 0 7930 7960 7960 789079807900 7940795 0 868085308650 871079107920 7940 7920854079508630 792079307860835079407910 86707 98 079207850 85308640 796079007870 837078607860 8620795079407900 796079307930 7890 7930 7950836079207 9 3 0 79207930 8 0 7 07890 SalvationAstorMoc kl i nRiversideDitch M o c k l i n Mocklin Neale Avenue and OK Flats Basin N02 N01 N04N12 N05 N20 N13N15 N25 N14 N21 N03 N17 N24 N06 N23 N19 N18 N09 N10 N22 N08 N07 N11 N26 N16 OFALL-4 OFALL-3 OFALL-2 OFALL-1 OFALL-DWS OFALL-P03-N16 0 300 Feet o Drainage Basins and SWMM Routing Elements Neale Avenue and OK Flats Basin Page 3 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 3 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Storages Dry Well ?>Pond UT Underground Storage Conduit Overflow Outlet Weirs Legend ^_Mine Flow Sources %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water P61I. !!!!!!! ! ! ! ! ! !!!?> ?> ?> ?> ^_%O %O %O ECOOPERAVE PARKAVEMCSKI MMI NGRDSWESTENDSTUTEPLMIDLANDAVEEASTWOOD DR KINGST WESTVIEW DR WATERSAVE SKIMMINGLNROARING FORK DRARDMOREDR WLUPI NEDRNORTHWAYDRRIVERSIDEDRSRIVERSIDEAVEASPEN GROVE RD QUEENST CLEVELANDSTCRYSTALLAKERDFREDLNMASCOTTELN DALEAVE ARDMORECTALICELNALPINE CTNRIVERSIDEAVELACETCT EHOPKINSAVE EHYMANAVE R04 R03 R02 R01 R14 R17 R12 R18 R20 R13 R05 R10 R08 R16 R09 R06 R15 J25-R05 J23-R13 J21-R19 J20-R19 J19-R05 J18-R05 J17-R08 J16-R10 J09-R09P02-R13 P01-R15 P04-R08N P03-R08S DW01-R07 Unknown Source RoaringForkRiverSnyder Park Herron Park Garrison Park 8110809081208100 8080 8070 8130 806 0 8 0 4 08050 8030 80208140815081608010800081707990 8180819079708200821082208230824079608250 8260 8270 8280829083008310 832083307950 83408350 8360 8370 8380 83908400841084208430 794084408450846084708480 7980849085008510 852085307930854085507910 7 9 2 0 8 5 6 0 7900 857085807890859086008610 862086308640 7880 8010801 0 8010 855079207950 7950 79908030 7980 7950 79407970 7930 8000 7930 79408140 81608010798079408000 8150 8060 8000 808079607940 8010 859085708030 8 0 2 0 7 9 6 0 7920 8 0 3 0 80007960 85408050 7980 79908000 7960 8 1 2 0 8040 7980 8020 7950 811080008070 80107 98 0 805080607960 80308 6 0 07930 7990 8 0 0 07970807080007940 8170 80208010 8150 8180858079 50 809079808060 7980 80208140 80007940 80107 9 8 0 807081208010 7990 8030 8020 7 9 6 0 80007940 806079407930Salvat i onRiversideDitchAstor Riverside McSkimming Basin R04 R01 R05 R02 R08 R13 R11 R09 R19 R07 R10 R16 R03 R14 R15 R12 R06 R17 R20 R18 OFALL-14 OFALL-10 OFALL-09 OFALL-08 OFALL-07 OFALL-06 OFALL-05 OFALL-04 OFALL-DW01-R07 R19 R07 R11 D05-R19 0 300 Feet o Drainage Basins and SWMM Routing Elements Riverside McSkimming Basin Page 4 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 4 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Divider Outfall Storages Dry Well ?>Pond Conduit Overflow Outlet Weirs Legend ^_Mine Flow Sources %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water P62I. E06 E03 E01 E04 J06-E02 J05-E02 J04-E06 J02-E06 J01-E06 Roaring Fork River 8050 8 0 6 0 8070 808080908110 8100 81708180 813081208160819081508140820082108220823082408040825082608270 82808290830083108030 83208330802083408350836083708380839084008410842084308010 84408 0 0 0 84508460847084808490850085108520853085407 9 9 0 855085608570858085908600861086208630864086508660 8670868086908700 8 1 6 0 8 0 2 0 8060 8030819080308 1 4 0 8 0 3 08060 8 1 2 0 80808 15 0 8030 8050 8 0 3 08010 80308450809080908030 833084408060 81408030 8 0 1 0 80008190 8 0 5 0 8050 8060 8 0 4 080408070 8140 8140 8430809081108160 8150 8040804080308180812081608150 8 0 3 0 8 0 7 0 8030Sal vat i onEastwood Basin E02 E04 E03 E06 E05 E01 OFALL-01 OFALL-02 E05 E02 D02-E06 HWY82MTNLAURELDREASTWOOD DR WESTVIEW DR ROARINGFORKDR WLUPINEDRNORTHWAYDRASPEN GROVE RD ELUPI NEDRLUPINEDR FABI LOOP MC S K IM MIN G R D STILLWATERDRALICELNCRYSTALLAKERDMCSKIMMINGRD 0 200 Feet o Drainage Basins and SWMM Routing Elements Eastwood Basin Page 5 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 5 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Divider Outfall Conduit Overflow Legend Topographic Contour Interval = 10 feet Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water P63I. ?>HWY82MTNLAURELDRELUPI NEDRWESTVIEW DR EASTWOOD DR WLUPINEDRSTILLWATERDRSTILLWATERLN ROARING FORK DR NORTHWAYDRFABILOOPLUPINEDR MTNLAURELCTMTNLAURELDR Roari ngForkRi verSal vat i onStillwater Bridge Basin S03 S01 S08 S04 S05 S07 S10 S09 S06 S12 S02 S11 P01-S07 OFALL-2 OFALL-1 S09 S08 S02 S12 S10 S11 S04 S07 S06 S05 S01 S03 J08-S08 J07-S12 J06-S10 J05-S10 J04-S07 J02-S08 J01-S02 0 200 Feet o Drainage Basins and SWMM Routing Elements Stillwater Bridge Basin Page 6 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-03 SWMM Routing 6 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Storages ?>Pond Conduit Overflow Weirs Legend Topographic Contour Interval = 10 feet Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Surface Water P64I. !!!!!!! !!!!!!!!!!!!!! !!"Hunter Creek Basin Gibson Avenue Basin Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Eastwood Basin Stillwater Bridge Basin RoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENAST8100 90009100920093009 40 0 95009600970098008000 10300104007900 102001 0 1 0 010000 87 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001030010200820086008100 8900 8300 9 9 0 0 90008600890080001 0 3 0 0 101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010000840080008000870080008500 9500850088000 1,000 Feet o Hydrologic Soil Groups Smuggler/Hunter Surface Drainage Master Plan 2.4 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-04 Hydrologic Soil Groupsr90.mxd Plot Date: 1/9/2015 Legend !!Irrigation Ditch, Culvert Irrigation Ditch, Open Topographic Contour (feet NGVD29) Major Basins Hydrologic Soil Groups Hydrologic Group B Hydrologic Group C Hydrologic Group D Water P65I. !!!!!!! !!!!!!!!!!!!!! !!"Hunter Creek Basin Gibson Avenue Basin Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Eastwood Basin Stillwater Bridge Basin RoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENAST8100 90009100920093009 40 0 95009600970098008000 10300104007900 102001 0 1 0 010000 87 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001030010200820086008100 8900 8300 9 9 0 0 90008600890080001 0 3 0 0 101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010000840080008000870080008500 9500850088000 1,000 Feet o Initial Soil Infiltration Rates Smuggler/Hunter Surface Drainage Master Plan 2.5 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-05 Initial Soil Infiltrationr90.mxd Plot Date: 1/9/2015 Legend !!Irrigation Ditch, Culvert Irrigation Ditch, Open Topographic Contour (feet NGVD29) Major Basins Legend Initial Rate (in/hr) < 2.41 2.42 - 3.48 3.49 - 4.19 4.20 - 4.44 4.45 - 4.50 P66I. !!!!!!! !!!!!!!!!!!!!! !!"Hunter Creek Basin Gibson Avenue Basin Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Eastwood Basin Stillwater Bridge Basin RoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENAST8100 90009100920093009 40 0 95009600970098008000 10300104007900 102001 0 1 0 010000 87 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001030010200820086008100 8900 8300 9 9 0 0 90008600890080001 0 3 0 0 101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010000840080008000870080008500 9500850088000 1,000 Feet o Existing Land Use Smuggler/Hunter Surface Drainage Master Plan 2.6 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-06 Existing Land User90.mxd Plot Date: 1/9/2015 Legend !!Irrigation Ditch, Culvert Irrigation Ditch, Open Topographic Contour (feet NGVD29) Major Basins Classification, Percent Impervious Low Density Residential, 22% Medium Density Residential, 55% High Density Residential, 90% Industrial Area, 80% Park/Cemetery, 5% Open Space/Undeveloped, 2%P67I. P68I. April 2015 2-19 | Stormwater Runoff and Drainage Facility Capacity Analysis For the determination of imperviousness, the land uses and areas within each basin were identified and the surface imperviousness percentages and depression losses were selected for each type of land use by referring to the tables from the URMP and USDCM Volume 1 (References 1 and 55). For different classes of residential development, the suggested imperviousness percentages were selected based on the residential categories compiled from the Aspen’s and Pitkin County’s zoning plan. Table 2.6 lists the adopted imperviousness parameters for each land use type, respectively. The computed area-weighted land use parameters for each sub-basin as well as the GIS layers are included in Appendix B. Table 2.6 Adopted Land Use Characteristics and Parameter Values (Based on the Guidelines from the URMP and USDCM Volume 1) Zoning Description UDFCD Land Use Class % Imperviousness Impervious Depression Loss (in) Pervious Depression Loss (in) Low Density Residential (LOWRES) Single Family (0.5/ac) 22 0.05 0.35 Medium Density Residential (MRES) Single Family (4/ac) 55 0.05 0.35 High Density Residential (MFRES) Single Family (15/ac) 90 0.1 0.35 Mining (IND) Industrial (Light Areas) 80 0.1 0.35 Parks & Cemeteries (PARK) Parks, Cemeteries 5 0.05 0.4 Open Space (OS) Undeveloped Areas 2 0.05 0.4 Notes: ac = acre; % = percent 2.5.1.6 CUHP Results The parameters described in the previous sections were estimated for each sub-basin then inputted into CUHP to estimate the total peak outflow from each sub-basin. A summary of sub- basin peak outflow rates is presented in Table 2.7. The sub-basin ID shown in Table 2.7, such as H01, corresponds to a given sub-basin in each major basin. H01 corresponds to an upstream sub-basin in the Hunter Creek Basin with sequential sub-basin numbering increasing to the most downstream sub-basin. Sub-basins along with major basins can be seen on Figure 2.3. The CUHP 2005 input and output files, outflow hydrographs, and flood volumes for all sub-basins are included Appendix B. P69 I. 2-20 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 Table 2.7 CUHP 2005 Results – Sub-basin Peak Outflow Sub-Basin ID Peak Flow (cfs) 2-year 5-year 10-year 25-year 50-year 100-year Hunter Creek Basin H01 0.1 0.2 0.5 1.5 1.9 8.8 H02 0.1 0.2 0.4 0.8 1.2 2.3 H03 1.3 1.9 2.6 4.3 5.5 8.6 H04 1.8 2.3 2.8 3.7 4.3 5.4 H05 7.2 9.8 12.1 16.1 18.7 22.2 Gibson Avenue Basin G01 1.3 1.8 2.5 4.1 5.2 7.9 G02 0.6 0.7 0.9 1.4 1.7 2.2 G03 0.6 0.9 1.1 1.4 1.6 1.8 G04 0.2 0.4 0.6 1.3 1.6 3.1 G05 7.1 9.6 11.7 15.7 18.2 21.5 G06 1.4 1.9 2.3 3.1 3.6 4.3 G07 0.5 0.7 0.8 1.2 1.4 1.8 G08 2.8 3.7 4.5 6.2 7.2 8.7 G09 0.6 0.8 0.9 1.3 1.6 2.0 G10 0.5 0.7 0.9 1.2 1.4 1.6 G11 0.3 0.3 0.4 0.6 0.7 0.9 G12 0.1 0.1 0.1 0.2 0.2 0.3 G13 0.8 1.0 2.5 4.1 5.2 7.9 Neale Avenue and OK Flats Basin N01 0.1 0.2 0.5 1.8 2.3 7.6 N02 0.0 0.1 0.3 1.0 1.3 8.8 N03 0.0 0.0 0.0 0.2 0.2 2.0 N04 1.1 1.4 1.8 3.0 3.7 5.5 N05 0.0 0.0 0.1 0.2 0.2 1.0 N06 0.0 0.0 0.0 0.1 0.2 0.6 N07 0.2 0.3 0.4 0.6 0.7 1.0 N08 0.1 0.1 0.2 0.3 0.4 0.7 N09 0.0 0.0 0.0 0.0 0.1 0.6 N10 0.4 0.5 0.7 1.0 1.2 1.7 N11 0.4 0.5 0.7 0.9 1.1 1.2 N12 6.0 8.5 10.5 13.9 16.0 18.2 N13 1.6 2.0 2.5 3.7 4.4 5.8 N14 1.2 1.6 1.9 2.9 3.4 4.7 N15 2.3 3.1 3.8 5.3 6.3 7.8 P70 I. April 2015 2-21 | Stormwater Runoff and Drainage Facility Capacity Analysis Table 2.7 CUHP 2005 Results – Sub-basin Peak Outflow Sub-Basin ID Peak Flow (cfs) 2-year 5-year 10-year 25-year 50-year 100-year N16 0.5 0.7 0.8 1.1 1.3 1.4 N17 1.7 2.2 2.7 3.7 4.4 5.5 N18 1.7 2.2 2.7 3.6 4.1 5.0 N19 1.8 2.4 3.0 3.9 4.5 5.4 N20 2.1 2.6 3.2 4.6 5.5 7.6 N21 2.3 3.0 3.6 4.9 5.8 7.3 N22 0.9 1.2 1.4 2.0 2.3 2.8 N23 0.8 1.1 1.4 2.0 2.5 3.4 N24 0.7 0.9 1.1 1.7 2.0 2.7 N25 2.3 3.1 3.8 5.4 6.5 8.7 N26 0.0 0.1 0.1 0.2 0.2 0.3 Riverside McSkimming Basin R01 0.1 0.1 0.4 1.2 1.6 6.4 R02 0.0 0.1 0.2 0.6 0.7 2.5 R03 2.2 2.8 3.4 4.7 5.6 7.4 R04 3.0 4.4 6.0 10.1 12.9 20.7 R05 4.9 6.3 7.6 10.7 12.7 16.4 R06 0.0 0.0 0.1 0.2 0.3 0.9 R07 2.9 3.7 4.5 6.4 7.6 10.1 R08 6.7 8.9 10.8 14.6 17.1 19.8 R09 1.5 1.9 2.4 3.7 4.6 6.4 R10 2.7 3.5 4.2 5.8 6.9 8.9 R11 3.6 4.8 5.8 8.1 9.6 12.4 R12 1.4 1.9 2.3 3.1 3.7 4.5 R13 3.3 4.3 5.2 7.3 8.7 11.2 R14 0.6 0.7 0.9 1.3 1.6 2.1 R15 4.2 5.6 6.8 10.1 12.0 15.2 R16 1.8 2.3 2.8 4.0 4.9 6.4 R17 0.7 0.9 1.1 1.5 1.8 2.3 R18 0.8 1.0 1.2 1.7 2.0 2.4 R19 3.5 4.5 5.4 7.5 8.9 11.5 R20 0.7 0.9 1.1 1.5 1.8 2.5 Eastwood Basin E01 0.0 0.1 0.2 0.9 1.1 10.1 E02 10.0 12.7 15.5 21.8 26.1 35.2 E03 0.1 0.1 0.2 0.5 0.8 2.1 P71 I. 2-22 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 Table 2.7 CUHP 2005 Results – Sub-basin Peak Outflow Sub-Basin ID Peak Flow (cfs) 2-year 5-year 10-year 25-year 50-year 100-year E04 0.1 0.1 0.3 0.9 1.2 4.6 E05 1.3 1.8 2.2 3.0 3.6 4.3 E06 0.8 1.1 1.3 1.9 2.2 2.9 Stillwater Bridge Basin S01 0.1 0.2 0.8 2.8 3.6 32.5 S02 0.6 0.8 0.9 1.3 1.5 2.1 S03 0.3 0.5 0.8 1.5 1.9 4.1 S04 1.8 2.4 2.9 4.1 4.8 6.3 S05 1.7 2.2 2.7 3.7 4.5 6.0 S06 0.9 1.3 1.5 2.1 2.5 3.2 S07 2.1 2.7 3.3 4.5 5.4 6.4 S08 2.2 2.8 3.4 4.8 5.7 7.8 S09 1.0 1.3 1.6 2.2 2.6 3.4 S10 1.8 2.3 2.8 3.9 4.7 5.6 S11 0.4 0.5 0.6 0.9 1.1 1.3 S12 0.0 0.1 0.1 0.3 0.5 1.0 Notes: cfs = cubic feet per second; ID = Identification 2.5.2 Hydrograph Routing InfoSWMM, developed by Innovyze, Inc., was used for hydrologic routing within the watershed. Within InfoSWMM, the sub-basins of each major basin are connected to nodes which represent confluences of flow or flow regime changes. Each node is linked to conduits representing the conveyance elements of the storm drainage system in the basin (overland flow paths, channels, storm sewer pipes, and culverts) for hydrograph routing. Routing schematics of the connectivity of the sub-basins, and routing elements are shown for each major basin on Figure 2.3. Each major basin figure shows the InfoSWMM elements used to model the basin (conduits, junctions, dividers, weirs, orifices, outlets, storage elements, and outfalls). These elements used in the InfoSWMM model to represent the drainage networks in the Study are generally described in Table 2.8 below, along with an example element ID. Every element in the InfoSWMM model is labeled with an alpha-numeric identifier (Element ID) describing the type of element and its location by sub-basin. For example, a divider element in sub-basin H01 of the Hunter Creek Basin would be labeled DXX-H01. The XX represents the number of the element. Each type of element in each sub-basin is generally numbered upstream to downstream, so lower numbers are in the upper parts of the basins. P72 I. April 2015 2-23 | Stormwater Runoff and Drainage Facility Capacity Analysis Table 2.8 InfoSWMM Model Elements Element Sample ID Description Conduit C03-G06 Conduits model the flow path from node to node and take into account the attenuation of flow over a specified length based on the roughness of the travel path. They represent open channel flow (along roads, natural swales, or unconfined overland flow paths), storm sewer systems, or culverts. Overflow O03-G06 Overflows are associated with other elements to model flow that exceeds the capacity of the element or “overflows” to a downstream location. Overflows are most typically associated with underground conduits. See the Divider description below. Junction H03 or J03-G06 Junctions are modeled nodes to where multiple conduits can converge and inflow hydrographs are summed. Junctions labeled with a single alpha- numeric ID are the locations where the CUHP hydrograph for a sub-basin is entered into the InfoSWMM model. Junctions with a dual ID represent the location where multiple conduits converge. There can only be one outflow from a junction. Divider D03-G02 Dividers are nodes that can have multiple inflows but two outflows. The primary outflow is a pipe or culvert of interest. The primary pipe or storm system carries the maximum flow allowable and the excess flow is conveyed out of the divider as Overflow (usually in a road side ditch or curb and gutter) to another specified downstream node to maintain continuity in the model. Storage DW08-G03 – Dry Well P03-N16 – Pond or Underground Storage Storage elements represent areas that can store runoff and attenuate flow depending on the designated outflow from the storage element. A detention pond can be modeled with an outlet structure InfoSWMM element coupled with a weir element to signifying overtopping of the pond. A retention pond is modeled with no outlet element and only has a weir element which flows when the storage element has reached capacity. Dry wells are differentiated from other storage elements using the ID. Weir WEIR01-N04 Weirs are used to model overtopping flows from storage elements. Weirs can be the only outlet of a storage area or they can be coupled with an orifice outlet structure element. Outlets OLET-DW02- N04 Outlets are outlet elements used to model the pipe or culvert outlet of a storage element. A stage-discharge curve is developed for each unique storage and outlet paring to signify the outflow through a pipe as head increases in the storage element. Outfall OFALL-1 Outfalls are nodes where all inflow in a basin model exits the model, usually outside of the project area or to a major river or stream. In this study, these are usually to the Roaring Fork River or to Hunter Creek. Notes: CUHP = Colorado Urban Hydrograph Procedure; ID = Identification 2.5.2.1 Channel Routing The Kinematic Wave routing method was selected for the channel routing component of the InfoSWMM model, and is recommended by the U.S. Army Corps of Engineers (USACE) over other methods for channels with geometry similar to the channels in Aspen (References 34 and 49). Geometric information for each of the conveyance elements, i.e., length, slope, Manning’s roughness coefficient, and physical dimensions of each link, were entered into the InfoSWMM model using GIS methods. Typical cross-sectional dimensions for natural channel reaches were developed within the model using InfoSWMM’s Transect Extractor tool. This tool automatically P73 I. 2-24 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 takes a cross-section of a channel based on the topography supplied. Typical road cross-sections for local and residential roads, each with a rural and urban option, were adopted from Aspen’s Design Standards (Reference 10) and were manually entered within each major basin’s InfoSWMM model. The Manning’s roughness coefficient (n-value) for each channel reach was selected by inspection of the 2010-aerial photography, land use, and field visits. Some portions of the Study Area have been channelized in developments or along roads. Conveyance types and “n” values for the study area are listed in Table 2.9. Table 2.9 Manning’s N-Values for Conveyance Elements Conveyance Type Manning’s Roughness Coefficient Natural Channel Grass-lined 0.04 Constructed Ditch Earthen 0.03 Roadside Ditch, Overflow Grass-lined 0.04 Road Runoff Paved 0.016 Culvert Concrete 0.013 Culvert HDPE 0.012 Culvert PVC 0.011 Culvert Metal 0.024 Notes: HDPE = high density polyethylene; PVC = polyvinyl chloride 2.5.2.2 Storage Routing The numerous dry wells, private detention areas, and underground infiltration basins in the Study Area were modeled as storage elements (detention or retention areas) based on the surveyed or observed characteristics of each location. Stage-versus-storage relationships were developed for each existing area from the best available topography, either the 1- or 2-foot contours. These calculations are contained in Appendix B. In the Study Area, multiple dry wells exist. Dry wells were modeled as described in Aspen’s Design Standards (Reference 10) and American Society for Testing and Materials (ASTM) Designation C 444 – 03 for Perforated Concrete Pipe (Reference 2) with an assumed hydraulic conductivity of three inches/hour and a constant one foot/foot hydraulic gradient. Each dry well was assumed to be 6 feet in diameter with varied depths based on the 2012 survey data with no initial water storage. Surveyed dry wells were found to be significantly silted in and depths could only be measured to the observed bottom which was typically silt; therefore, the true depth of each dry well is unknown. Perforations in each dry well were assumed to be in the bottom 3 feet of the surveyed depth with an impervious bottom. Overflow from each dry well was assumed to act as a broad-crested weir with an estimated weir coefficient of 3. Information on the surveyed dry wells has been incorporated into Aspen’s GIS database. P74 I. April 2015 2-25 | Stormwater Runoff and Drainage Facility Capacity Analysis In addition to dry wells, two underground infiltration basins reside within the Study Area: one in the Gibson Avenue Basin P01-G03) and the other in the Neale Avenue and OK Flats Basin (P03- N16). Each of these storage areas were treated as retention elements as there is no evidence of an outlet structure. The underground infiltration basin located in the Gibson Avenue Basin was modeled with geometry specified by obtained as-built drawings. The modeled geometry for the infiltration basin in the Neale Avenue and OK Flats Basin was estimated based on aerial photography and topography. The entire bottom of each infiltration basin was assumed to be pervious with a hydraulic conductivity of 3 inches/hour with impervious sides. Both infiltration basins were assumed to have no outlet pipe and were modeled with weir overflows once storage capacity was reached. Both retention elements were modeled with no initial water storage. Multiple private detention ponds were entered into each model with stage-storage geometry based on the best available topography of 1- or 2-foot contours. Several ponds were observed to be full; therefore, initial water surface elevations were assumed to equal the crest of each pond, which results in negligible attenuation at each storage element. Ponds were chosen to be modeled based on their potential affects to stormwater runoff. If a pond was evident based on GIS data or aerial photography and its size was thought to be large enough to attenuate stormwater flow (by engineering judgment), the pond was modeled within InfoSWMM. Otherwise, several private, aesthetic ponds were omitted from the analysis. Especially if the pond was near the Roaring Fork River and was deemed a direct flow area. Two retention areas (storage areas with no observed or surveyed outlet pipe), one located just above the Riverside Ditch diversion in the Riverside McSkimming Basin (P01-R15) and the other at the downstream end of the Smuggler Mine in the Neale Avenue and OK Flats Basin (P02-N01), were modeled with no outlet pipes and were both shown to retain all contributing flows up to the 100-year event. There were no areas of standing water observed in study area, and therefore, groundwater was not assumed to influence stormwater runoff characteristics. All InfoSWMM storage element output, including peak flows and volumes, are in Appendix B. All stage-storage calculations for each storage element modeled are in Appendix B. 2.6 HYDRAULICS Hydraulic analyses were conducted for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence interval flood events for each major basin shown in Figure 2.1. 2.6.1 Modeling Criteria Data for use in structure evaluations in the hydraulic analysis were selected on a structure-by- structure basis. Where survey data was not found, field notes were referenced first, followed by as-builts, then estimates based on aerial and topography. Hydraulic conveyance and performance were evaluated within InfoSWMM and FlowMaster (Reference 6). Manning’s n values were estimated based on aerial photography for each flow type. All major outfalls for each InfoSWMM model either discharge into the Roaring Fork River or Hunter Creek. The starting tailwater elevation for each model was assumed to be the 10-year flood event water surface elevation estimated from the Flood Insurance Study for Pitkin County, Colorado and Incorporated Areas, revised October 19, 2004 (Reference 16). P75 I. 2-26 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 2.6.2 Open Channels Unless noted otherwise, open channels (natural and roadway) were analyzed using InfoSWMM and Manning’s equation. If flooding occurred in an element during the 100-year event, or where the depth of flow exceeded the typical channel cross-section, a Hydrologic Engineering Centers River Analysis System (HEC-RAS) model or FLO-2D model was developed to depict the 100- year flooding extents (see Section 2.6.4). Digital files for the HEC-RAS and FLO-2D models are included in Appendix B. 2.6.3 Culverts Cross culverts were analyzed using InfoSWMM. When the capacity of a culvert was not reached during the 100-year event, FlowMaster (Reference 6) was used to calculate the culvert’s capacity. Digital files for the Flowmaster and InfoSWMM calculations are included in Appendix B. 2.6.4 Storm Sewers The capacity of each storm sewer conduit element was taken as the conduit flow from which the lowest return period causes overflow plus an additional 15 percent to account for the uncertainties associated with hydrologic and hydraulic analysis. For example, if a 24-inch pipe has a 5-year flow of 25 cfs and no overflow but in the 10-year event has a flow of 33 cfs and an overflow of 2 cfs, the capacity of the pipe is assumed to be 33 cfs plus an additional 15 percent, or approximately 38 cfs. If a pipe did not achieve a full flow condition during the 100-year event, a FlowMaster analysis was conducted for each pipe section to determine the pipe’s capacity. Digital files for the Flowmaster calculations are included in Appendix B. 2.6.5 Floodplain Modeling Where the capacity of a surface flow conduit such as a channel or roadway was exceeded and where flows are conveyed in unconfined surface flow paths, there is potential for flooding of residences or other structures. The hydraulic function of these potential flooding paths (See Figure 2.7) was evaluated using surface flow methods based on a set of flow and depth criteria to see if HEC-RAS floodplain modeling would be needed. The evaluated reaches are listed below in Table 2.10. The evaluation criteria to determine if surface flow analysis would be needed are as follows: 1. Flows were greater than or equal to 10 cfs. 2. There is a known reported flood problem in the area. 3. Flow is immediately adjacent to an existing structure 4. The normal flow depth is greater than 6-inches. If a reach satisfied any of the criteria, the reach was first modeled in FlowMaster to determine if the 4th criterion was satisfied using the most upstream InfoSWMM node 100-year flow and estimated cross-section. If the cross-section resulted in a flow depth less than 6-inchs, the reach was not evaluated further in HEC-RAS and was deemed to be a low flood threat. Table 2.10 lists all the potential flow reaches analyzed, the associated 100-year flow rate, the flow depth (if analyzed), and the conclusion for further analysis. P76 I. !!!!!!!!!!!!!! !!!! !!!! ! !%, %, %O %O HunterCreek RoaringForkRiver H04 Gibson Ave. Aspen Art Museum Park 7 9 7 0 7880 7950 7960 787079407860793078907910 7 9 2 079007850 7980 7990800080108020784080308040783079307 8 3 0 78507980 79007890 78907860 79407940 7 8 5 0 7900 79507880786079107 8 8 0 7840 7930 7 8 3 0 7840 78307840784079007960 7 8 4 0 78707910 797078907890 8 0 3 0 7 8 9 0 79507970793079307880 7 9 2 0 7 8 4 07890 7 9 1 07840 7940 7940 7880 78907 9 2 0 7920 78407 9 3 0 79007 9 3 0 7960SalvationM o c k l i n M o c k l i n Mocklin M o ck lin Hunter Creek BasinHunter Creek Basin H03 H05 H02 H04 H01 REDMTNRDSPRUCESTLONEPINERD VINESTGIBSONAVE TEALCTNMILLSTSPRUCECTWILLIAMS WAY RACESTBROWNLNS H A D Y L N PUPPYSMI THSTNSPRI NGSTCOWENHOVENCTWALNUT STINDEPENDENCEPL BRENDENCTOFALL-13 OFALL-12 OFALL-11 H02 H05 H03 H01 People have to sandbag Basement flooding in 2006 storm. 0 200 Feet o Problem Areas Hunter Creek Basin Page 1 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 1 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall Conduit Overflow Conduit, 100yr Flooding Conduit, Surface Flow Legend %,Known Deficiencies %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water Existing 100-yr Floodplain P77I. !!!!!!!!!!!!!! !!!! !!!! ! ! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!%, %, UT %O %O G03J06-G10 J05-G10 J04-G10 J03-G08 J02-G08 J01-G05 J03-G06 J02-G03 J01-G06 P01-G03 DW07-G03 DW05-G03 DW04-G03 DW02-G04 DW01-G04 DW06-G03 DW08-G03 DW03-G03 OFALL-2 OFALL-5 OFALL-4 OFALL-3 OFALL-1 OFALL-DW OFALL-P01-G03 G08 G13 G11 G09 G12 G10 G05 G07 G06 G04 G02 G01 D10-G10 D09-G10 D08-G08 D08-G10 D07-G09 D06-G02 D05-G02 D03-G02 D02-G02 SPRUCE ST PARKCIRLONEPINERD NSPRI NGSTVINESTRACESTTEALCTAJAXAVEBROWNLNNICHOLASLNSPRUCECTWILLIAMSWAYWALNUTST WILLIAMSRANCHDRS OU T H AVE FREESILVERCTCOWENHOVENCTINDEPENDENCEPLPeople have to sandbag Basement flooding in 2006 storm. Gibson Ave. Aspen Art Museum Park Roar i ngFor kRi ver 7880 7890798079707990 8000801079407950 796079007 9 2 07910 7930787080207860803080408050806080708080 7850809081007840811081208130814081508160817081808190789080207960 7 8 7 0 7 8 9 0 79307860 7 8 7 0 796078707890 7890 78507880 7870 78707860 7 9 1 0 7940 78707910 7 8 4 0 7 8 4 0 79607880 8030789079 1 0 809080407890 7880 7900 79407 8 8 0 7940 7 9 3 07910 7930795079007860 79407930 79507 9 2 0 78607850Gibson Avenue Basin SalvationMocklin M o c k l i n Mocklin G05 G08 G13 G06 G04 G07 G09 G01 G02 G11 G10 G03 Hunter Creek G12 0 200 Feet o Problem Areas Gibson Avenue Basin Page 2 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 2 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall Dry Well UT Underground Storage, None Dry Well, <2yr Capacity Conduit Overflow Orifices Outlet Weirs Conduit, < 2yr Conduit, 100yr Flooding Conduit, Surface Flow Overflow, 100yr Flooding Legend %,Known Deficiencies %O Potential Water Quality Locations Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water Existing 100-yr Floodplain!!!!!!!!!!! ! ! ! ! ! ! ! !!!!!!!!!!!UT G03 J03-G06 J02-G03 J01-G06 G04 G02 G01D06-G02 D05-G02 D03-G02 D02-G02 OFALL-DW OFALL-P01-G03 P01-G03 DW07-G03 DW06-G03 DW05-G03 DW04-G03 DW03-G03 DW02-G04 DW01-G04 DW08-G03798080007990 801079708020 80308040 7960 8 0 1 0 80108010Salvation G05 G04 G02 G03 G01 SILVERLODEDR TEALCTWILLIAMSRANCHDRP78I. !!!!!!!!!!!!!! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! ! ! ! !!!%, %, %, %, %, UT ^_ ^_ ^_ %O %O %O %O SOUTH AV E N16 N25 N22 N26 N11 N01 N06 N03 J20-12 J24-N17 J23-N24 J22-N23 J19-N12 J16-N13 J15-N10 J14-N12 J13-N12 J12-N12 J11-N10 J10-N10 J09-N10 J08-N10 J07-N05 J06-N10 J04-N05 J03-N09 J21-N23 J18-N17 RoaringForkRiver GIBSONAVE PARKCIREHYMANAVE EHOPKINSAVE SMUGGLERMTNRDSPRUCESTSILVERLODEDROAKLNLONEPINERD PARKAVENSPRINGSTNEALEAVE VINEST SSPRINGSTEMAINST KINGSTMAPLELNRACEST SORIGINALSTTEALCTAJAXAVEMIDLANDAVENI CHOLASLNQUEEN STWALNUTST COTTONWOODLNRIOGRANDEPL WILLIAMSRANCHDRSWESTENDSTECOOPERAVE WILLIAMSWAYARDMOREDRMASCOTTE LN CLEVELANDSTBAYST FREESI LVERCTCOWENHOVENCTEFRANCISST EBLEEKERST MATCHLESSDRHAROLDROSSCTREGENTSTBRENDENCT EHOPKINSAVENSPRINGSTP03-N16 P02-N01 DW01-N10 DW02-N04 N14 N24 N23 N21 N20 N19 N18 N15 N17 N12 N13 N07 N02 N10 N08 N05 N09 D2-N12 J17-N17 D13-N23 D11-N21 D10-N21 D09-N21 D08-N21 D07-N21 D06-N26 D05-N21 D04-N20 D03-N19 D01-N02 D01-N06 N04 D12-N23 System needed in area Dry well plugged and floods System needed to drain low spot Basement flooding in 2006 storm. Snowmelt flooding. Localized flooding. No outlet. Gibson Ave. Herron Park Garrison Park N. Spring St. Johnson Shaft Unknown Source Mollie Gibson Shaft7980 81108000797079908010802080408030805080608070 832083108080830080908100829083308280827081208260825082408130814079608150816081708230818082008190822082108340835079508360837079408380 7 9 3 0 8390840084108420843084407920 845084608470848084908500851085207910 7900 853078908540 8550 85608570858085907880 7870 8 6 0 0 861078608620 8630864086508670 86608680 86908700 78508710 8070 8610 79607 8 8 0 869080607920 7 9 3 0 7960 8120 7850 87008660 7 9 3 0 7880791079507970 8600 7910 79707880 80507 9 2 0 793 0 7960 7960 789079807900 7940795 0 868085308650 871079107920 7940 7920854079508630 792079307860835079407910 86707 98 079207850 85308640 796079007870 83707860 862079507900 796079307930 7890 7930 795083607 9 2 0 7 9 3 0 79207930 8 0 7 07890 SalvationAstorMoc kl i nRiversideDitch M o c k l i n Mocklin Neale Avenue and OK Flats Basin N02 N01 N04N12 N05 N20 N13N15 N25 N14 N21 N03 N17 N24 N06 N23 N19 N18 N09 N10 N22 N08 N07 N11 N26 N16 OFALL-4 OFALL-3 OFALL-2 OFALL-1 OFALL-DWS OFALL-P03-N16 0 300 Feet o Problem Areas Neale Avenue and OK Flats Basin Page 3 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 3 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall Dry Well, <2yr Capacity UT Underground Storage, <2yr Capacity Conduit Overflow Outlet Weirs Conduit, < 2yr Conduit, < 5yr Conduit, 100yr Flooding Conduit, Surface Flow Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water Existing 100-yr Floodplain P79I. !!!!!!! ! ! ! ! ! !!!%, %, %, ?> ?> ?> ?> ^_%O %O %O ECOOPERAVE PARKAVEMCSKI MMI NGRDSWESTENDSTUTEPLMIDLANDAVEEASTWOOD DR KINGST WESTVIEW DR WATERSAVE SKIMMINGLNROARING FORK DRARDMOREDR WLUPI NEDRNORTHWAYDRRIVERSIDEDRSRIVERSIDEAVEASPEN GROVE RD QUEENST CLEVELANDSTCRYSTALLAKERDFREDLNMASCOTTELN DALEAVE ARDMORECTALICELNALPINE CTNRIVERSIDEAVELACETCT EHOPKINSAVE EHYMANAVE R04 R03 R02 R01 R14 R17 R12 R18 R20 R13 R05 R10 R08 R16 R09 R06 R15 J25-R05 J23-R13 J21-R19 J20-R19 J19-R05 J18-R05 J17-R08 J16-R10 J09-R09P02-R13 P01-R15 P04-R08N P03-R08S DW01-R07 System needed in area Dry well plugged and floods Snyder Park Herron Park Garrison Park Unknown Source RoaringForkRiver8110809081208100 8080 8070 8130 8 06 0 8 0 4 08050 8030 80208140815081608010800081707990 8180819079708200821082208230824079608250 8260 8270 8280829083008310 832083307950 83408350 8360 8370 8380 83908400841084208430 794084408450846084708480 7980849085008510 852085307930854085507910 7 9 2 0 8 5 6 0 7900 857085807890859086008610 862086308640 7880 80108 01 0 8010 85507 9 2 0 7950 7950 79908030 7980 7950 7970 793 0 8000 7930 79408140 81608010798079408000 8150 8060 8000 808079607940 8010 859085708030 8 0 2 0 7 9 6 0 7920 8 0 3 0 80007960 85408050 7980 79908000 7960 8 1 2 0 8040 7980 8020 7950 811080008070 80107 9 8 0 80508060 80308 6 0 07930 7990 8 0 0 07970807080007940 8170 80208010 8150 8180858079 50 809079808060 7980 80208140 80007940 80107 9 8 0 807081208010 7990 8030 8020 7 9 6 0 80007940 806079407930Salvat i onRiversideDitchAstor Riverside McSkimming Basin R04 R01 R05 R02 R08 R13 R11 R09 R19 R07 R10 R16 R03 R14 R15 R12 R06 R17 R20 R18 OFALL-14 OFALL-10 OFALL-09 OFALL-08 OFALL-07 OFALL-06 OFALL-05 OFALL-04 OFALL-DW01-R07 R19 R07 R11 D05-R19 0 300 Feet o Problem Areas Riverside McSkimming Basin Page 4 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 4 of 6r90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall ?>Pond, None Dry Well, <2yr Capacity Conduit Overflow Outlet Weirs Conduit, < 2yr Conduit, < 5yr Conduit, 100yr Flooding Conduit, Surface Flow Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water Existing 100-yr Floodplain P80I. E06 E03 E01 E04 J06-E02 J05-E02 J04-E06 J02-E06 J01-E06 Roaring Fork River 8050 8 0 6 0 8070 808080908110 8100 81708180 813081208160819081508140820082108220823082408040825082608270 82808290830083108030 83208330802083408350836083708380839084008410842084308010 84408 0 0 0 84508460847084808490850085108520853085407 9 9 0 855085608570858085908600861086208630864086508660 8670868086908700 8 1 6 0 8 0 2 0 8060 8030819080308 1 4 0 8 0 3 08060 8 1 2 0 80808 15 0 8030 8050 8 0 3 08010 80308450809080908030 833084408060 81408030 8 0 1 0 80008190 8 0 5 0 8050 8060 8 0 4 080408070 8140 8140 8430809081108160 8150 8040804080308180812081608150 8 0 3 0 8 0 7 0 8030Sal vat i onEastwood Basin E02 E04 E03 E06 E05 E01 HWY82MTNLAURELDREASTWOOD DR WESTVIEW DR ROARINGFORKDR WLUPINEDRNORTHWAYDRASPEN GROVE RD ELUPI NEDRLUPINEDR FABI LOOP MC S K IM MIN G R D STILLWATERDRALICELNCRYSTALLAKERDMCSKIMMINGRD OFALL-01 OFALL-02 E05 E02 D02-E06 0 200 Feet o Problem Areas Eastwood Basin Page 5 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 5 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall Conduit Overflow Conduit, < 5yr Conduit, 100yr Flooding Legend Topographic Contour Interval = 10 feet Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water Existing 100-yr Floodplain P81I. ?>HWY82MTNLAURELDRELUPI NEDRWESTVIEW DR EASTWOOD DR WLUPINEDRSTILLWATERDRSTILLWATERLN ROARING FORK DR NORTHWAYDRFABILOOPLUPINEDR MTNLAURELCTMTNLAURELDR Roari ngForkRi verSal vat i onStillwater Bridge Basin S03 S01 S08 S04 S05 S07 S10 S09 S06 S12 S02 S11 P01-S07 OFALL-2 OFALL-1 S09 S08 S02 S12 S10 S11 S04 S07 S06 S05 S01 S03 J08-S08 J07-S12 J06-S10 J05-S10 J04-S07 J02-S08 J01-S02 0 200 Feet o Problem Areas Stillwater Bridge Basin Page 6 of 6 Smuggler/Hunter Surface Drainage Master Plan 2.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig2-07 Problem Areas 6 of 6r90.mxd Plot Date: 1/9/2015 InfoSWMM Elements Junction Junction, No Storm System Divider Outfall ?>Private Pond, <2yr Capacity Conduit Overflow Weirs Conduit, 100yr Flooding Conduit, Surface Flow Legend Topographic Contour Interval = 10 feet Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Surface Water Existing 100-yr Floodplain P82I. April 2015 2-33 | Stormwater Runoff and Drainage Facility Capacity Analysis Table 2.10 Floodplain Assessment by Sub-basin Sub- basin ID InfoSWMM Conduit 100-year Flow (cfs) Comments Estimated Flow Depth (ft) Final Analysis Hunter Creek Basin H03 C19-H02 2.3 <10 cfs and no buildings in flow path - No further analysis, minimal flood threat C56-H03 8.8 Reported flooding area - 100-yr floodplain HEC-RAS model from H01 to OFALL-11 C57-H03 15.8 >10 cfs with known flooding area upstream - 100-yr floodplain HEC-RAS model from H01 to OFALL-11 Gibson Avenue Basin G01, G02, G03, G04 System to J03-G06 3.1 <10 cfs and system has 100- yr capacity - No further analysis, minimal flood threat G05 J03-G06 to G05 3.1 Evaluated in FlowMaster to determine flow depth at C10-G05 by structure. Downstream is conveyed by either road, ditch, or parking lots. 0.17 < 0.5 feet depth, minimal flood threat G05, G08, G06, G11, G10 G05 to OFALL-2 22-33 >10 cfs that flows through developments - 100-yr floodplain HEC-RAS model from G05 to OFALL-2 Neale Avenue & OK Flats Basin N02, N07, N12 System to D15-N-12 9.6 <10 cfs and system is conveyed in roadway and away from structures - No further analysis, minimal flood threat N17, N15, N25 J17-N17 to OFAL-1 23-44 >10 cfs near that flows through development - 100-yr floodplain FLO-2D model from J17-N17 to OFALL- 1 Riverside McSkimming Basin R09 C36-R09 12.4 >10 cfs near a private residence, Evaluated in FlowMaster 0.36 < 0.5 feet depth, minimal flood threat R13 C61-R13 2.1 <10 cfs and 1-ft contours do not capture roadway visible swale. - No further analysis, minimal flood threat R13 C47-R13 11.2 >10 cfs near a private residence, Evaluated in FlowMaster 0.17 < 0.5 feet depth, minimal flood threat R19 C23-R04 20.7 >10 cfs near a private residence, evaluated in FlowMaster 0.45 < 0.5 feet depth, flow conveyed in swale around homes, minimal flood threat R02, R03, R08 System to P04-R08N 2.6-8 <10 cfs and follows natural swales around structures - No further analysis, minimal flood threat R01, R05 R01 to 6.4 <10 cfs and conveyed in - No further analysis, minimal P83 I. 2-34 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 Table 2.10 Floodplain Assessment by Sub-basin Sub- basin ID InfoSWMM Conduit 100-year Flow (cfs) Comments Estimated Flow Depth (ft) Final Analysis Midland Ave. roadway flood threat R06, R05 R06 to Park Ave. 0.9 <10 cfs and conveyed in roadway and parking lots - No further analysis, minimal flood threat R05 R07 to OFALL-04 10.2-35 >10 cfs near private residences - 100-yr floodplain HEC-RAS model from R07 to OFALL-2 including lower section of C44- R05 downstream of Midland Ave. Eastwood Basin E03, E04, E01 E03 to J06- E02 16.8 >10 cfs along roadway, roadway swales have capacity to convey 100-year event. - No further analysis, minimal flood threat E02, E06 J06-E02 to OFALL-01 16.8-35 >10 cfs that flows through developments - 100-yr floodplain HEC-RAS model from J06-E02 to OFALL- 01 Stillwater Bridge Basin S03, S06, S08 C05-S06 & C20-S08 4.1-6.1 <10 cfs and follows natural swales around structures - No further analysis, minimal flood threat S05, S08 C07-S08 6 <10 cfs but modeled lower section between two structures - 100-yr floodplain HEC-RAS model of lower section of C07- S08 S01, S02, S08, S09, S11 S01 to OFALL-2 33-41 >10 cfs near private residences - 100-yr floodplain HEC-RAS model from S01 to OFALL-2 S04, S07, S10, S12 S04 to OFALL-1 12-Jun >10 cfs near private residences - 100-yr floodplain HEC-RAS model from S04 to OFALL-1 Notes: cfs = cubic feet per second; ft = feet; HEC-RAS = Hydrologic Engineering Centers River Analysis System; ID = Identification Based on the above criteria and the results stated in Table 2.10, six reaches required a HEC-RAS analysis to map the 100-year floodplain extents. Each estimated floodplain was estimated using the USACE’s HEC-RAS River Analysis System Model, version 4.1.0 (Reference 48), to perform one-dimensional, steady-flow hydraulic calculations for each specified reach’s extents. Geometric data for the HEC-RAS model were generated in an ArcMap® GIS environment using the USACE’s HEC-GeoRAS extension to create a geospatially referenced hydraulic model. 1-ft contours were used where available. 2-ft contours were used for areas where the 1-ft contours did not extend. The 100-year channel top width water surface extents calculated in HEC-RAS were then inputted back into GeoRAS and the floodplain was delineated using the water surface extents as a guideline and manipulated using engineering judgment with the aid of contours, aerials, determined curb/gutter sections, and flows around structures. One reach in the Neale Avenue and OK Flats Basin has complex topography and a suspected split flow along Park Circle. For this reach, FLO Engineering’s FLO-2D two-dimensional hydraulic model, Version 98.1, was used (Reference 17). The base mapping from the mudflow analysis, discussed in Section 3, was adopted to estimate flooding along Park Circle in the reach from the Brown Lane and Park Circle intersection to the outfall to the Roaring Fork River past P84 I. April 2015 2-35 | Stormwater Runoff and Drainage Facility Capacity Analysis East Francis Street, because of significant development in this area which divides the flow. All resulting 100-year floodplain delineations for each major basin are shown in Figure 2.7. It should be noted that these floodplain delineations are more representative of the extents of surface flow than the conduits shown in Figure 2.7 as these flow paths include detailed calculations taking into account the available contours whereas the conduits are merely a routing mechanism to move flow around in the basin from one location to another. 2.7 DRAINAGE SYSTEM CAPACITY Peak flows and corresponding hydraulic capacity for open channels, culverts, storm sewer systems, dry wells, and detention and retention areas are summarized in Table 2.11 for each node in each basin from upstream to downstream with associated downstream connected conduits. Detailed results are discussed in the following paragraphs. Problem Areas, which are areas with insufficient capacity or flooding issues, identified through the study or by citizens and Aspen staff and the approximate 100-year floodplains generated by HEC-RAS and FLO-2D, are shown on Figure 2.7. 2.7.1 Summary by Basin The following subsections discuss the drainage system capacities for each major basin in detail. For each major basin, refer to Figure 2.7 to see the locations of the capacity issues discussed relative to each element ID in the model. Refer back to Section 2.5.2 for the general descriptions of the types of elements used in the model. Table 2.11 shows the tabulated results for each major basin by element, as well as the calculated capacity issues from upstream to downstream in reference to each node along a flow reach. In areas where there is a cross-culvert or a storm system, a divider node was used to estimate the capacity of the pipe downstream. Any flow that is not conveyed in the downstream pipe is labeled as “overflow” in Table 2.11 and carried downstream to the next node. Figure 2.7 shows each major basin’s model layout and the stormwater problem areas tabulated in Table 2.11. P85 I. 2-36 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 This page intentionally left blank P86 I. Table 2.11 Rainfall Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year H01 C56-H03 -Spruce St. & Spruce Ct.Overland runoff 55.5 Local -0.1 0.2 0.5 1.5 1.9 8.8 0.1 0.2 0.5 1.5 1.9 9 ------ H02 C19-H02 -Salvation Ditch Overflow Overland runoff 8.7 --0.1 0.2 0.4 0.8 1.2 2.3 0.1 0.2 0.3 0.8 1.1 2.3 ------ OFALL-11 --Williams Woods Outfall Outfall 77.7 --1.3 2.0 3.0 6 8 18 ------------ H05 C58-H05 -Overland runoff Swale 11.5 --7 10 12 16 19 22 7 10 12 16 19 22 ------ OFALL-12 --Hunter Creek Development Outfall Outfall 11.5 --7 10 12 16 19 22 ------------ H04 C59-H04 O59-H04 Red Mountain Road Bridge Inlet 12" CMP 3.0 Local 6 1.8 2.3 2.8 3.7 4.4 5 1.8 2.3 2.8 3.7 4.4 5 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-13 --Red Mountain Road Bridge Outfall Outfall 3.0 --1.8 2.3 2.8 3.7 4.4 5 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15%. * Approximate values. **Assumed pipe size Green = Sufficient Capacity Red Mountain road Outfall Hunter Creek Development Outfall Williams Wood Outfall Hunter Creek Basin Contributing Area (ac) Road Classification Capacity (cfs) Conduit IDSWMM Element ID Location Existing Structure Description Overflow ID Conduit OverflowFlow Rates (cfs) Page 1 of 6 P87I. Table 2.11 Rainfall Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year G04 C06-G04 O06-G04 Silverlode Dr. (West)12" HDPE 12.62 Local 11 0.2 0.4 0.6 1.3 1.6 3.1 0.2 0.4 0.6 1.3 1.6 3.1 0.0 0.0 0.0 0.0 0.0 0.0 DW01-G04 ORI01-G04 WEIR01-G04 Silverlode Dr. (West)12" CMP/ Dry Well 12.62 Local 6 0.2 0.4 0.6 1.3 1.6 3.1 0.2 0.4 0.6 1.3 1.6 3.0 0.0 0.0 0.0 0.0 0.0 0.0 DW02-G04 OLET-DW02-G04 WEIR02-G04 Silverlode Dr. (West)Dry Well 12.62 Local 0.0 0.2 0.4 0.6 1.3 1.6 3.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.4 0.6 1.3 1.6 3.0 G02 C05-G02 O05-G02 Silverlode Dr. (Center)24" RCP 2.57 Local 36 0.6 0.7 0.9 1.4 1.7 2.2 0.6 0.7 0.9 1.4 1.7 2.2 0.0 0.0 0.0 0.0 0.0 0.0 D05-G02 C04-G02 O04-G02 Silverlode Dr. (Center)24" CMP 2.57 -58 0.6 0.7 0.9 1.4 1.7 2.2 0.6 0.7 0.9 1.4 1.7 2.2 0.0 0.0 0.0 0.0 0.0 0.0 D06-G02 C03-G02 O03-G02 Silverlode Dr. (Center)24" CMP 2.57 -30 0.6 0.7 0.9 1.4 1.7 2.2 0.6 0.7 0.9 1.4 1.7 2.2 0.0 0.0 0.0 0.0 0.0 0.0 G01 C01-G01 O01-G01 Williams Ranch Dr. (East)24" RCP 12.32 Local 54 1.3 1.8 2.5 4.1 5 8 1.3 1.8 2.5 4.1 5 8 0.0 0.0 0.0 0.0 0.0 0.0 D02-G02 C02-G02 O02-G02 Williams Ranch Dr. (East)24" CMP 12.32 Local 49 1.3 1.8 2.5 4.1 5 8 1.3 1.8 2.5 4.1 5 8 0.0 0.0 0.0 0.0 0.0 0.0 D03-G02 C07-G02 O07-G02 Upper Gibson Ave Confluence 36" CMP 14.89 -83 1.8 2.5 3.3 6 7 10 1.8 2.5 3.3 6 7 10 0.0 0.0 0.0 0.0 0.0 0.0 DW08-G03 OLET-DW08-G03 WEIR03-G03 1st Dry Well in Series Dry Well 1 15.51 -0.0 2.3 3.0 4.0 6 7 11 0.0 0.0 0.0 0.0 0.0 0.0 2.3 3.0 4.0 6 7 11 DW05-G03 OLET-DW05-G03 WEIR04-G03 2nd Dry Well in Series Dry Well 2 15.51 -0.0 2.3 3.0 4.0 6 7 11 0.0 0.0 0.0 0.0 0.0 0.0 2.3 3.0 4.0 6 7 11 DW06-G03 OLET-DW06-G03 WEIR06-G03 3rd Dry Well in Series Dry Well 3 15.51 -0.0 2.3 3.0 4.0 6 7 11 0.0 0.0 0.0 0.0 0.0 0.0 2.5 3.0 4.0 6 8 11 DW03-G03 OLET-DW03-G03 WEIR07-G03 4th Dry Well in Series Dry Well 4 15.51 -0.0 2.5 3.0 4.0 6 8 11 0.0 0.0 0.0 0.0 0.0 0.0 2.6 3.2 4.0 6 8 11 DW07-G03 OLET-DW07-G03 WEIR08-G03 5th Dry Well in Series Dry Well 5 15.51 -0.0 2.6 3.2 4.0 6 8 11 0.0 0.0 0.0 0.0 0.0 0.0 2.3 3.2 4.0 6 8 11 DW04-G03 OLET-DW04-G03 WEIR09-G03 6th Dry Well in Series Dry Well 6 15.51 -0.0 2.3 3.2 4.0 6 8 11 0.0 0.0 0.0 0.0 0.0 0.0 2.3 3.2 4.0 6 8 11 P01-G03 OLET-P01-G03 WEIR10-P01-G03 Underground Seepage Area Seepage Area 15.51 -22 2.3 3.2 4.0 6 8 11 0.2 0.4 0.5 0.9 1.0 1.5 0.0 0.0 0.0 0.0 0.0 0.0 J03-G06 C10-G05 -Confluence of Upper Gibson Confluence 28.13 --0.2 0.4 0.6 1.3 1.6 3.0 0.2 0.4 0.6 1.3 1.6 3.0 ------ G05 C12-G05 O12-G05 Lone Pine Rd Crossing 18" CMP**39.63 Local 9 8 10 12 16 19 22 8 9 9 9 9 9 0.0 1.4 3.6 8 10 13.4 G13 C13-G13 O13-G13 Lone Pine Rd. Grate Inlet 18" CMP 42.31 Local 12 9 10 10 11 11 12 8 10 10 11 11 12 0.0 0.0 0.0 0.0 0.0 0.2 G08 C27-G08 O27-G08 River Bluff Townhome Intake 8" PVC**47.72 -1.4 11 13 14 16 18 20 1.4 1.4 1.4 1.4 1.4 1.4 10 12 13 15 17 18 D08-G08 C25-G08 O25-G08 River Bluff Townhome Outlet 6" CPP 47.72 -0.5 1.4 1.4 1.4 1.4 1.4 1.4 0.5 0.5 0.5 0.5 0.5 0.5 0.9 0.9 0.9 0.9 0.9 0.9 D09-G10 C24-G10 O24-G10 Red Mtn Rd. off road 18" CMP 47.72 -7 10 12 13 15 17 18 8 8 8 8 8 8 2.2 4.7 6 8 9 11 D10-G10 C31-G10 O31-G10 Red Mtn Rd. crossing 12" CMP**47.72 -8 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-2 --Red Mtn. Rd. Outfall Outfall 47.72 --1.4 1.4 1.4 1.4 1.4 1.4 ------------ G06 C16-G06 O16-G06 Lone Pine Rd. & Rd Mtn. Rd.24" CMP 2.40 Local 32 1.4 2.7 5 10 12 17 1.4 2.7 5 10 12 17 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-1 --Lone Pine Rd. Outfall Outfall 2.40 --1.4 2.7 5 10 12 17 ------------ G07 C19-G09 O19-G09 Gibson Ave. Storm System 24" CMP 1.46 Local 27 0.5 0.7 0.8 1.2 1.4 1.8 0.5 0.7 0.8 1.2 1.4 1.8 0.0 0.0 0.0 0.0 0.0 0.0 D07-G09 C20-G09 O20-G09 Gibson Ave. Stem 18" CMP 1.46 -15 0.5 0.7 0.8 1.2 1.4 1.8 0.5 0.7 0.8 1.2 1.4 1.8 0.0 0.0 0.0 0.0 0.0 0.0 G09 C22-G09 O22-G09 Gibson Ave. Curb Inlet 12" PVC 2.91 Local 10 0.6 0.8 1.0 1.3 1.6 2.0 0.6 0.8 1.0 1.3 1.6 2.0 0.0 0.0 0.0 0.0 0.0 0.0 D08-G10 C21-G10 O21-G10 Gibson Ave. Storm Stem 18" CMP 2.91 -7 1.1 1.4 1.8 2.4 2.9 3.8 1.1 1.4 1.8 2.4 2.9 3.8 0.0 0.0 0.0 0.0 0.0 0.0 G10 C18-G11 O18-C11 Red Mtn Rd Crossing 18" CMP 51.29 Local 15 11 14 16 19 21 24 11 14 16 18 18 18 0.0 0.0 0.0 2.1 4.0 7 OFALL-3 --Gibson Ave. Outfall Outfall 51.29 --11 14 16 19 21 24 ------------ G11 C17-G11 O17-G11 Bridge Curb Inlet at N. Mill St.12" CMP 0.67 Local 4 0.3 0.4 0.4 0.6 0.7 0.9 0.3 0.4 0.4 0.6 0.7 0.9 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-4 --N. Mill St. Bridge Outfall (N.)Outfall 0.67 --0.3 0.4 0.4 0.6 0.7 0.9 ------------ G12 C23-G12 O23-G12 Bridge Grate Inlet at N. Mill St.12" CMP 0.19 Local 8 0.1 0.1 0.1 0.2 0.2 0.3 0.1 0.1 0.1 0.2 0.2 0.3 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-5 --N. Mill St. Bridge Outfall (S.)Outfall 0.19 --0.1 0.1 0.1 0.2 0.2 0.3 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15%. * Approximate values. **Assumed pipe size. Conduit ID Overflow ID Upper Gibson Ave. Basin Lone Pine Rd. Gibson Ave. Storm System N. Mill St. Bridge Gibson Avenue Basin Conduit OverflowFlow Rates (cfs) Green = Sufficient Capacity SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity* (cfs) Page 2 of 6 P88I. Table 2.11 Rainfall Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 19 0.0 0.0 0.1 0.3 0.3 2.5 0.0 0.0 0.1 0.3 0.3 2.5 0.0 0.0 0.0 0.0 0.0 0.0 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 4.2 0.0 0.0 0.1 0.3 0.4 2.8 0.0 0.0 0.1 0.3 0.4 2.8 0.0 0.0 0.0 0.0 0.0 0.0 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local -0.0 0.0 0.1 0.3 0.4 2.8 0.0 0.0 0.1 0.3 0.4 2.8 ------ N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 7 0.0 0.0 0.2 0.4 0.6 3.8 0.0 0.0 0.1 0.4 0.6 3.8 0.0 0.0 0.0 0.0 0.0 0.0 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 --0.1 0.2 0.6 1.8 2.2 8 0.0 0.0 0.0 0.0 0.0 5 ------ N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 25 0.1 0.1 0.2 0.3 0.4 0.7 0.1 0.1 0.2 0.3 0.4 0.7 0.0 0.0 0.0 0.0 0.0 0.0 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local -0.1 0.1 0.2 0.3 0.4 5 0.1 0.1 0.2 0.3 0.4 5 ------ J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local -0.1 0.1 0.2 0.7 0.9 7 0.1 0.1 0.2 0.7 0.9 7 ------ N04 C16-N04 O16-N04 Silverlode Dr.12" CMP 9.1 Local 4 1.4 1.8 2.4 3.7 4.6 6 1.4 1.8 2.4 3.6 3.7 3.7 0.0 0.0 0.0 0.3 1.1 3.0 N11 C25-N04 -Silverlode Dr.Road runoff 0.7 Local -0.4 0.5 0.7 0.9 1.1 1.2 0.4 0.5 0.6 0.9 1.0 1.2 ------ DW02-N04 OLET-DW02-N04 WEIR01-N04 Silverlode Dr. & Smuggler Mtn. Rd.Dry Well 9.1 Local 0.0 1.4 1.8 2.4 3.9 4.6 6 0.0 0.0 0.0 0.0 0.0 0.0 5 7 8 9 10 13 N10 C12-N10 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 12" CMP 90.0 Local 4 4.0 6 6 9 9 13 3.4 3.7 3.7 3.9 3.9 3.9 0.3 1.4 1.8 4.7 6 10 DW01-N10 OLET-DW01-N10 WEIR02-N10 Park Cir. & Smuggler Mtn Rd.Dry Well 90.0 Local 0.0 3.4 3.7 3.7 3.9 3.9 3.9 0.0 0.0 0.0 0.0 0.0 0.0 8 9 10 9.1 10 10 N13 C29-N13 O29-N13 End of Tributary at Brown Ln.12" PVC 95.7 Local 2.1 6 9 9 15 15 19 2.2 2.1 2.2 2.1 2.2 2.1 3.6 7 6 13 13 17 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -95 0.0 0.1 0.3 1.0 1.3 9 0.0 0.1 0.3 1.0 1.3 9 0.0 0.0 0.0 0.0 0.0 0.0 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 75 0.0 0.1 0.3 1.0 1.3 9 0.0 0.1 0.3 1.0 1.3 9 0.0 0.0 0.0 0.0 0.0 0.0 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 10 0.2 0.3 0.4 0.6 0.7 1.0 0.2 0.3 0.4 0.6 0.7 1 0.0 0.0 0.0 0.0 0.0 0.0 J20-12 C34-N12 -Free Silver Ct. roadside Ditch Ditch 60.9 --0.2 0.4 0.6 1.5 2.0 10 0.2 0.4 0.6 1.5 2.0 10 ------ J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local -0.2 0.4 0.6 1.5 2.0 10 0.2 0.4 0.6 1.5 2.0 10 ------ D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 11 0.2 0.4 0.6 1.5 2.0 10 0.2 0.4 0.6 1.5 2.0 10 0.0 0.0 0.0 0.0 0.0 0.0 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.12" PVC 60.9 Local 10 0.2 0.4 0.6 1.5 2.0 10 0.2 0.4 0.6 1.5 2.0 10 0.0 0.0 0.0 0.0 0.0 0.0 N12 C28-N12 O28-N12 Brown Ln & Park Cir.12" PVC 156.6 Local 8 8 11 13 16 18 20 7.7 8 8 8 8 8 0.3 2.9 4.9 8 10 13 D2-N12 C30-N12 O30-N12 Brown Ln Inlet to Infiltration Tank 24" PVC 163.3 Local 46 8 8 8 9 10 17 7.7 8 8 9 10 17 0.0 0.0 0.0 0.0 0.0 0.0 J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.Road runoff 163.3 Local -3.7 7 10 13 17 23 3.2 7 9 13 16 22 0.0 0.0 0.0 0.0 0.0 0.0 P03-N16 WEIR03-N16 -Centennial Apts. Underground Infiltration Tank 10'x80' Tank 163.9 -2 8 9 9 10 10 17 8.2 8.5 8.7 9.6 10.2 17.0 ------ J18-N17 C36-N17 O36-N17 Park Cir.Road runoff 163.9 Local -11 15 17 21 26 32 10 14 16 20 25 32 0.0 0.0 0.0 0.0 0.0 0.0 N17 C61-N17 O61-N17 Gibson Ave Inlet 12" CMP 167.5 Local 0.8 12 16 19 24 29 37 0.8 0.8 0.8 0.8 0.8 0.8 11 16 18 23 29 36 OFALL-1 --Oklahoma Flats Outfall Outfall 172.8 --13 18 22 29 35 44 ------------ N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 60 2.3 3.1 3.8 5 6 8 2.3 3.1 3.8 5 6 8 0.0 0.0 0.0 0.0 0.0 0.0 N18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 4 1.6 2.2 2.7 3.6 4.1 5 1.6 2.2 2.7 3.4 3.4 3.5 0.0 0.0 0.0 0.3 0.9 1.7 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 11 4.0 5 7 9 10 13 4.0 5.3 6.4 9 10 13 0.0 0.0 0.0 0.0 0.0 0.1 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 25 6 8 9 13 15 18 5.7 7.6 9.3 13 15 18 0.0 0.0 0.0 0.0 0.0 0.0 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 13 6 8 9 13 15 18 5.7 7.6 9.3 13 15 18 0.0 0.0 0.0 0.0 0.0 0.0 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 13 6 8 9 13 15 18 5.7 7.6 9.3 13 14 15 0.0 0.0 0.0 0.0 0.9 4.4 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 15 6 8 9 13 15 18 5.7 7.6 9.3 12 12 12 0.0 0.0 0.0 1.6 4.0 7 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 35 6 8 9 13 15 18 5.7 7.6 9.3 13 15 18 0.0 0.0 0.0 0.0 0.0 0.0 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 30 2.1 2.6 3.2 4.6 6 8 2.0 2.6 3.2 4.6 6 8 0.0 0.0 0.0 0.0 0.0 0.0 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 40 2.0 2.6 3.2 4.6 6 8 2.0 2.6 3.2 4.6 6 8 0.0 0.0 0.0 0.0 0.0 0.0 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 50 2.0 2.6 3.2 4.6 6 8 2.0 2.6 3.2 4.6 6 8 0.0 0.0 0.0 0.0 0.0 0.0 N21 C49-N23 O49-N23 Neale Ave & Gibson Ave Confluence 36" CMP 21.8 Local 85 10 13 16 22 26 32 10 13 16 22 26 32 0.0 0.0 0.0 0.0 0.0 0.0 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 33 11 14 17 24 28 35 11 14 17 24 28 36 0.0 0.0 0.0 0.0 0.0 0.0 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 27 11 14 17 24 28 36 11 14 17 24 27 27 0.0 0.0 0.0 0.0 3.1 11.2 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 1.4 0.0 0.0 0.0 0.0 3.1 11 0.0 0.0 0.0 0.0 3.1 3.4 0.0 0.0 0.0 0.0 0.0 7.8 OFALL-2 --Neale Ave. Outfall Outfall 24.8 --11 14 17 24 30 36 ------------ N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 9 1.5 1.9 2.2 3.2 3.7 5 1.5 1.9 2.2 3.2 3.7 5 0.0 0.0 0.0 0.0 0.0 0.0 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -19 1.6 1.9 2.3 3.3 3.9 5 1.5 1.9 2.3 3.3 3.9 5.3 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-3 --Smuggler Mine Outfall Outfall 5.6 --1.5 1.9 2.3 3.3 3.9 5 ------------ N22 C55-N24 -King St. (Flooding)Low Area; Flooding 1.7 Local -0.9 1.2 1.4 2.0 2.3 2.8 0.8 1.1 1.3 1.9 2.2 2.8 ------ OFALL-4 --Bibbig Exemption Outfall Outfall 5.1 --1.4 1.9 2.3 3.3 4.0 5 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15% for single piped systems and exact when determined in StormCAD (linked storm systems). *Estimated linked storm sytem capacities determined using StormCAD, Single element pipe capacity estimated as full-piped flow in FlowMaster. **Assumed pipe sizes. Neale Ave. and OK Flats Basin SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity* (cfs) Conduit ID Overflow ID Bibbig Exemption Riverside Ditch Outfall Conduit Overflow Oklahoma Flats Outfall Park Circle Tributary to Oklahoma Flats Outfall Neale Aven. Storm System Smuggler Mine Outfall Flow Rates (cfs) Green = Sufficient Capacity Page 3 of 6 P89I. Table 2.11 Rainfall Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OFALL-05 --Callahan Outfall Outfall 6.0 --1.8 2.3 2.8 4.0 4.9 6 ------------ P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 -32 4.2 6 7 10 12 15 0.0 0.0 0.0 0.0 0.0 0.0 ------ OFALL-09 --Gordon Outfall Outfall 1.3 --0.8 1.0 1.2 1.7 2.0 2.4 ------------ OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 --0.7 0.9 1.1 1.5 1.8 2.5 ------------ R14 C60-R13 -Salvation Ditch & Hwy 82 Road runoff 2.58 Local -0.6 0.7 0.9 1.3 1.6 2.1 0.6 0.7 0.9 1.3 1.6 2.0 ------ J23-R13 C61-R13 -Fred Ln. & Riverside Dr.Road runoff 2.58 Local -0.6 0.7 0.9 1.3 1.6 2.0 0.5 0.7 0.8 1.3 1.5 2.0 ------ P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 11.7 --3.3 4.4 5 8 9 12 3.3 4.3 5 8 9 12 ------ OFALL-07 WEIR06-P01-R15 -Gordon/Callhan 2 Outfall Outfall 11.7 --3.3 4.3 5 8 9 12 0.0 0.0 0.0 0.0 0.0 0.0 ------ R11 C16-R11 O16-R11 Eastwood Dr.12" CMP 7.7 Local 2.0 3.6 5 6 8 10 12 2.0 1.5 1.5 1.5 1.5 1.5 2.2 3.5 4.5 7 8 11 R09 C37-R19 -Hwy 82 Road runoff 15.7 Local -5 6 8 11 13 18 5 6 8 11 13 17 ------ R04 C23-R04 O23-R04 Salvation Ditch overflow Overland runoff 40.2 --3.0 4.4 6 10 13 21 2.9 4.3 6 10 13 21 ------ J21-R19 C55-R19 -Alpine Ct. & E. Cooper Ave.Confluence/Runoff 55.9 Local -8 10 13 21 26 37 8 10 13 21 26 37 ------ D05-R19 C50-R19 O50-R19 Midland Ave. & Cooper Ave.18" CMP 55.9 Local 13 8 10 13 21 26 37 8 10 13 13 13 13 0.0 0.0 0.7 8 13 24 R12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -1.4 1.9 2.3 3.1 3.6 4.5 1.4 1.9 2.3 3.1 3.6 4.5 ------ R17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.7 0.9 1.1 1.5 1.8 2.3 0.7 0.9 1.1 1.5 1.8 2.3 ------ J20-R19 C53-R19 -E. Cooper Ave. & Lacet Ln.Confluence/Runoff 4.7 Local -2.1 2.7 3.2 4.4 5 7 2.1 2.7 3.2 4.4 5 7 ------ R19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.18" CMP 68.4 Local 12 13 17 21 31 38 52 12 12 11 11 11 11 2.2 6 11 21 28 42 OFALL-10 --E. Cooper Ave. Outfall Outfall 68.4 --13 17 21 31 38 52 ------------ R02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.0 0.1 0.2 0.6 0.7 2.6 0.0 0.1 0.2 0.6 0.7 2.5 ------ R03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --2.2 2.8 3.4 4.7 6 7 2.1 2.7 3.3 4.7 6 7 ------ J17-R08 C43-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -2.1 2.8 3.4 4.8 6 8 2.1 2.7 3.3 4.7 5.7 8.0 ------ R08 C39-R08 -Snyder Park Overland runoff 10.0 --7 9 11 15 17 20 7 9 11 15 17 20 ------ P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --7 9 11 15 17 20 6 8 10 13 16 19 ------ P04-R08N WEIR02-P04-R08N -North Snyder Park Pond Aesthetic Pond 34.0 --8 10 13 17 21 26 8 10 13 17 21 26 ------ J16-R10 C40-R10 -Midland Ave. & E. Hopkins Road runoff 34.0 Local -8 10 13 17 21 26 8 10 13 17 21 26 ------ R10 C41-R10 -Park Ave. & E. Hopkins Ave.Road runoff 40.5 Local -10 14 17 23 27 35 10 14 17 23 27 35 ------ OFALL-06 --E. Hopkins Ave. Outfall Outfall 40.5 --10 14 17 23 27 35 ------------ R01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.1 0.2 0.4 1.2 1.6 6 0.1 0.2 0.4 1.2 1.6 6 ------ J18-R05 C44-R05 -Mascotte Ln. & Ardmore Dr.Road runoff 31.6 Local -0.1 0.2 0.4 1.2 1.6 6 0.1 0.1 0.4 1.2 1.6 6 ------ R06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.0 0.0 0.1 0.2 0.3 0.9 0.0 0.0 0.1 0.2 0.3 0.9 ------ J25-R05 C64-R05 -Miland Park Pl Road runoff 5.0 Local -0.0 0.0 0.1 0.2 0.3 0.9 0.0 0.0 0.1 0.2 0.3 0.9 ------ R07 C35-R07 O35-R07 Park Ave. & North side of Midland Ave.12" CMP 7.3 Local 11 2.9 3.7 4.5 6 8 10 2.9 3.7 4.5 6 8 10 0.0 0.0 0.0 0.0 0.0 0.0 DW01-R07 INFIL-DW01-R07 WEIR03-DW01-R07 Park Ave. & Midland Ave.Dry Well 12.3 Local 0.0 2.9 3.7 4.5 6 8 10 0.0 0.0 0.0 0.0 0.0 0.0 6 9 11 13 13 13 J19-R05 C46-R05 -Park Ave.Road runoff 12.3 Local -6 9 11 13 13 13 6 8 9 11 11 11 ------ R05 C45-R05 -Park Ave. & Regent St.Road runoff 51.6 Local -10 13 16 21 23 29 9 13 15 19 22 28 ------ OFALL-04 --Riverside Addition Outfall Outfall 51.6 --9 13 15 19 22 28 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15%. * Approximate values. **Assumed pipe size Riverside Addtion Outfall Flow Rates (cfs) Green = Sufficient Capacity E. Cooper Ave. Outfall E. Hopkins Ave. Outfall Callahan Outfall Gordon Outfall Gordon/Callahan 1 Outfall Gordon/Callahan 2 Outfall SWMM Element ID Location Existing Structure Description Overflow ID Conduit Overflow Callahan Sub OS Retention Riverside McSkimming Basin Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Page 4 of 6 P90I. Table 2.11 Rainfall Summary Table Page 5 of 6 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year E03 C04-E04 -Mtn. Laurel Dr.Road runoff 11.6 Local -0.0 0.1 0.2 0.5 0.8 2.1 0.0 0.1 0.2 0.5 0.8 2.1 ------ E04 C05-E01 -Mtn. Laurel Dr.Road runoff 40.5 Local -0.1 0.2 0.5 1.4 1.9 7 0.1 0.2 0.5 1.4 1.9 7 ------ E01 C06-E02 -Mtn. Laurel Dr. switchback Road runoff 125.6 Local -0.1 0.2 0.7 2.3 3.0 17 0.1 0.2 0.7 2.3 3.0 17 ------ J06-E02 C13-E02 -Mtn. Laurel Dr. & W. Lupine Dr.Road runoff 125.6 Local -0.1 0.2 0.7 2.3 3.0 17 0.1 0.2 0.7 2.3 3.0 17 ------ J05-E02 C12-E02 -Roaring Fork Dr.Road runoff 125.6 Local -0.1 0.2 0.7 2.3 3.0 17 0.1 0.2 0.7 2.3 3.0 17 ------ E02 C01-E02 O01-E02 Hwy 82 crossing 18" CMP 150.5 Local 9 10 13 16 22 26 35 9 9 9 9 9 9 2.0 5 8 14 18 27 D02-E06 C09-E06 O03-E06 Downstream culvert of Hwy 82 18" CMP 150.5 -21 10 13 16 22 26 35 10 13 16 21 21 21 ------ OFALL-01 --Knollwood Outfall Outfall 150.5 --10 13 15 23 26 35 ------------ E05 C02-E05 O02-E05 Hwy 82 crossing 18" CMP 2.6 Arterial 5 1.4 1.8 2.2 3.0 3.6 4.3 1.3 1.8 2.1 3.0 3.6 4.3 0.0 0.0 0.0 0.0 0.0 0.0 E06 C07-E06 -Salvation Ditch overflow Overland runoff 6.2 --1.9 2.4 3.0 4.1 5 7 1.9 2.4 3.0 4.1 4.9 7 ------ OFALL-02 --Stillwater Ranch Outfall Outfall 6.2 --1.9 2.4 3.0 4.1 5 7 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15%. * Approximate values. **Assumed pipe size Stillwater Ranch Outfall Knollwood Outfall Flow Rates (cfs) Green = Sufficient Capacity Eastwood Basin Contributing Area (ac) Road Classification Capacity (cfs) Conduit IDSWMM Element ID Location Existing Structure Description Overflow ID Conduit Overflow P91I. Table 2.11 Rainfall Summary Table Page 6 of 6 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year S01 C01-S02 -Upper Mtn. Laurel Dr. low spot Road runoff 328.8 Local -0.1 0.2 0.8 2.8 3.6 33 0.1 0.2 0.8 2.8 4 32 ------ S02 C03-S08 -Mtn. Laurel Dr. curve/low spot Road runoff 330.3 Local -0.6 0.8 1.0 3.1 4.0 33 0.6 0.8 1.0 3.1 4 33 ------ S03 C05-S06 -Upper Mtn. Laurel Dr. low spot Road runoff 12.4 Local -0.3 0.5 0.8 1.5 1.9 4 0.2 0.5 0.7 1.5 2 4 ------ S06 C20-S08 -Mtn. Laurel Dr. low spot Road runoff 14.5 Local -1.1 1.4 1.9 3.1 3.9 6 1.1 1.4 1.9 3.1 4 6 ------ J08-S08 C19-S08 -E. Lupine Dr.Confluence 344.8 Local -1.6 2.2 2.8 5 7 37 1.6 2.2 2.8 5 7 37 ------ S05 C07-S08 -Mtn. Laurel Dr. low spot Road runoff 4.3 Local -1.7 2.2 2.7 3.7 5 6 1.7 2.2 2.7 3.7 5 6 ------ S08 C06-S08 O06-S08 W. Lupine Dr. and Lupine Dr.Confluence 354.6 Local -6 7 9 13 16 41 6 7 9 13 16 41 0.0 0.0 0.0 0.0 0.0 0.0 S09 C22-S09 O22-S09 Hwy 82 & Stillwater Dr.Confluence 357.0 Arterial -6 8 10 15 18 41 6 8 10 15 18 41 0.0 0.0 0.0 0.0 0.0 0.0 OFALL-2 C21-S09 -Northern Outfall Outfall 0.8 --7 9 11 15 19 42 ------------ S04 C10-S07 -Mtn. Laurel Dr. S. low spot Road runoff 5.3 Local -1.8 2.4 2.9 4.1 5 6 1.8 2.4 2.9 4.0 5 6 ------ P01-S07 WEIR01-S07 -E. Lupine Dr. low spot Private Detention 8.9 Local -3.4 4.5 5 8 9 12 3 5 5 8 9 12 ------ S10 C14-S10 -Hwy 82 Confluence 11.9 Arterial -1.8 2.4 2.8 3.9 5 6 1.7 2.3 2.7 3.8 5 5 ------ OFALL-1 --Southern Outfall Outfall 13.8 --1.7 2.3 2.8 4.0 5 6 ------------ Capacity is sufficient if the flow rate is less than the capacity plus 15%. * Approximate values. **Assumed pipe size. South Outfall Stillwater Dr. Outfall Stillwater Bridge Basin SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Conduit OverflowFlow Rates (cfs) Green = Sufficient Capacity P92I. April 2015 2-43 | Stormwater Runoff and Drainage Facility Capacity Analysis 2.7.1.1 Hunter Creek Basin Existing System Description: The Hunter Creek Basin has a total drainage area of approximately 95.9 acres and is mostly developed with high density in the lower reaches transitioning to low density residential property around Spruce Street. The upper headwaters remained undeveloped and are designated open space. Drainage Deficiencies: As the basin name indicates, most of the flow from the Hunter Creek Basin flows through the residential area directly to Hunter Creek. There are known deficiencies within the basin. No storm conveyance system exists in the upper reaches of the basin so flow is primarily routed along major streets and natural swales. A resident below the intersection of Spruce Street and Spruce Court reportedly has had to sandbag during major storm events. Another property owner to the south along Spruce Street reported flooding during a major storm event in 2006. The 100- year floodplain was delineated from H01 to the outfall to Hunter Creek at OFALL-11. The delineated floodplain shows flow skirting the house reported to have to sandbag during precipitation events with a relatively shallow depth of approximately 3-inches adjacent to the house. In the area to the south along Spruce Street that is reported to have flooded in a 2006 storm event, there is a relatively new curb and gutter section beginning just northwest of the citizen’s house. It is suspected that this improvement was developed after the reported flooding and that any potential split flow from H01 would be conveyed along the road and away from the residence. The only storm conveyance system within the basin is a bridge inlet located on the east side of the Red Mountain Road bridge at H04; which was estimated to have 10-year capacity. 2.7.1.2 Gibson Avenue Basin Existing System Description: The Gibson Avenue Basin has a total drainage area of approximately 65.2 acres and is mostly developed with high and medium density residential property dominating areas in the lower elevation regions, closest to the Roaring Fork River. The upper headwaters are undeveloped and designated as open space. The upper headwaters of the Gibson Avenue Basin flow along Silverlode Drive where the majority of storm runoff empties into multiple lateral storm sewer systems that converge at an engineered underground infiltration basin coupled with multiple dry wells in series, just above Teal Court. Storm runoff then continues west along Spruce Street where it is conveyed through residential parking lots and landscaped swales until a crossing at Lone Pine Road. Storm runoff then continues to the west along Miners Trail Road where it meets a natural swale flowing to a parking lot, then passes through a gap between the townhomes to continue south along Red Mountain Road to the intersection with Gibson Avenue, where it crosses under the road to the outfall (OFALL-3) into the Roaring Fork River. A separate contributing area accumulates along Gibson Avenue which flows through a storm system, beginning just past the Lone Pine Road and Gibson Avenue intersection, and outfalls to the Roaring Fork River (OFALL-3), just on the east side of the North Mill Street bridge. Drainage Deficiencies: All dry wells were found to be inadequate to capture the 2-year event. The infiltration basin above Teal Court was able to capture up to the 100-year event with minimal overtopping. The cross-culvert under Lone Pine Road at G05 was shown to be able to convey up to the 5-year event. Overflow from larger storms goes to the northeast along Lone P93 I. 2-44 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 Pine Road to a grate inlet just before Red Mountain Road, which outfalls (at OFALL-1) to the Roaring Fork River. Lone Pine Road can convey the 100-year event with roadside curb and gutter flow. The grate inlet at G06 captures all runoff up to the 100-year event and passes it to the Roaring Fork River. The area downstream of the Lone Pine Road crossing experiences flooding in the 100-year event. A swale, evident from the 1-foot contours and aerial, flows through this developed area but overtops the banks during the 100-year event and skirts around multiple structures. An 8- inch inlet pipe at G08 cannot convey the 2-year event and overflow spills into the parking lot, flows through an opening between the townhouse developments and down to Red Mountain Road. Evaluated culvert crossings and storm interception systems downstream of G08 along Red Mountain Road were all found to be inadequate to pass the 5-year event. All other evaluated storm systems were found to convey the 10-year event or more. 2.7.1.3 Neale Avenue and OK Flats Basin Existing System Description: The Neale Avenue and OK Flats Basin has a total drainage area of approximately 208.5 acres. The lower elevations within the basin are made up of a mixture of medium and high density residential property. The Smuggler Mine is located near the center of the basin while the upper half of the basin remains undeveloped with designated open space. Two major drainage systems flow through the lower residential reaches of the Neale Avenue and OK Flats Basin and empty into the Roaring Fork River. The largest collects runoff along Park Circle from the major basin’s headwaters along Silver Lode Drive and Smuggler Mountain Road. The collected flow continues to the west down Park Circle through the Oklahoma Flats subdivision along East Francis Street before outfalling into the Roaring Fork River at OFALL-1. The second drainage system collects into two lateral storm sewer systems that empty into the trunk line that follows Gibson Avenue to the east and down Neale Avenue to its outfall on the upstream edge of the Neale Avenue bridge at OFALL-2. This system originates with 12-inch and 24-inch pipes that eventually lead to a 36-inch corrugated metal pipe (CMP) trunk line to the Roaring Fork River. The modeled mining retention area above Silverlode Drive at P02-N01 collects runoff from the Smuggler Mine and was found to retain the full 100-year runoff volume. A private underground detention area (P03-N16) within the Centennial Condominiums residential development collects flow from the contributing area within the development (Sub-basin N16) and all upstream flow contributing to Brown Lane. Drainage Deficiencies: Flow originating in the headwaters is collected and conveyed along Smuggler Mountain Road. When this runoff converges with flow from Silverlode Drive at DW01-N10, the two storm conduits coupled with dry wells DW02-N04 and DW01-N10 are unable to handle the 2-year event. These dry wells overflow into the road section along Park Circle, at its intersection with Brown Lane, which is unable to convey the 100-year event and spills into the Smuggler Park development to the south; flooding the lowest areas throughout the Oklahoma Flats subdivisions downstream along East Francis Street as well as Gibson Avenue and South Avenue. The Neale Avenue and OK Flats sub basin that originates in the Smuggler Park development was estimated to be able to convey the up to the 50-year event with the exception of a 12-inch CMP (located at D13-N23) along the Neale Avenue Bridge at its outfall. P94 I. April 2015 2-45 | Stormwater Runoff and Drainage Facility Capacity Analysis A separate underground detention area is located north of the intersection of Brown Lane and Park Circle. The underground detention area (P03-N16), assumed to be hydraulically connected to the street runoff from Park Circle, is unable to handle the 2-year event and provides no attenuation of storm runoff in the area. A known deficiency was reported along King Street where there is a localized depression in the road with no storm sewer system at N22. Water Quality Capture Volume Analysis: The Neale Avenue and OK Flats Basin was selected as a pilot study to evaluate impacts to peak flows and total runoff volumes for the 2-, 5-, and 10-year events from applying 100%, 75%, 50%, and 25% of the water quality capture volume (WQCV) for the impervious areas of each sub-basin. Per the URMP (Reference 1), in Aspen, the WQCV to treat 100% of the impervious area for each watershed is 0.26 watershed inches. Figure 8.13 from the URMP provided a curve for the “Effective Impervious of Tributary Area to BMP (percent)” to determine the resulting fractional WQCV for the 75%, 50%, and 25% treatment options, shown in Table 2.12. Table 2.12 Determined WQCV Watershed Depth for Percentages of the Total WQCV Implementation Percent of WQCV Treatment (%) WQCV (watershed-inches) 100 0.26 75 0.154 50 0.098 25 0.056 Notes: % = Percent; WQCV = Water Quality Capture Volume These WQCV depths were added on to the original estimated values for impervious depression storage in the CUHP model for each fractional WQCV scenario within the Neale Avenue and OK Flats Basin. The results of the InfoSWMM-routed WQCV scenarios are summarized in Table 2.13. Generally, applying the WQCV is most effectual at the 75% and 100% levels in the 10-year storm event. For the more frequent events (e.g., the 2-year event), the reduction in flows is minimal. P95 I. 2-46 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 This page intentionally left blank P96 I. Table 2.13 WQCV Summary Table Page 1 of 3 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 0 0 0 0 1 0.0 0.0 0.0 0.0 0.0 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 -3 4 5 6 6 0.0 0.1 0.1 0.1 0.1 N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 1 1 1 2 2 0.0 0.0 0.0 0.1 0.1 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local 1 1 1 2 2 0.0 0.0 0.0 0.1 0.1 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local 1 1 1 2 2 0.0 0.0 0.0 0.1 0.1 N04 C16-N04 O16-N04 Silverlode Dr.12" CMP 9.1 Local 14 21 25 29 33 0.3 0.8 1.0 1.2 1.4 N11 C25-N04 -Silverlode Dr.Road runoff 0.7 Local 2 3 4 5 5 0.1 0.2 0.3 0.4 0.4 DW02-N04 OLET-DW02-N04 WEIR01-N04 Silverlode Dr. & Smuggler Mtn. Rd.Dry Well 9.1 Local 14 21 25 29 33 0.3 0.8 1.0 1.2 1.4 N10 C12-N10 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 12" CMP 90.0 Local 16 25 37 40 42 1.8 3.9 4.0 4.9 4.0 DW01-N10 OLET-DW01-N10 WEIR02-N10 Park Cir. & Smuggler Mtn Rd.Dry Well 90.0 Local 16 25 37 40 42 1.4 3.1 3.2 3.8 3.4 N13 C29-N13 O29-N13 End of Tributary at Brown Ln.12" PVC 95.7 Local 20 36 57 61 69 1.6 3.0 5 6 6 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -1 1 1 1 1 0.0 0.0 0.0 0.0 0.0 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 1 1 1 1 1 0.0 0.0 0.0 0.0 0.0 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 2 4 4 5 5 0.1 0.1 0.2 0.2 0.2 J20-12 C34-N12 -Free Silver Ct. roadside Ditch Ditch 60.9 -3 4 5 6 7 0.1 0.1 0.2 0.2 0.2 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local 3 4 5 6 7 0.1 0.1 0.2 0.2 0.2 D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 3 4 5 6 7 0.1 0.1 0.2 0.2 0.2 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.12" PVC 60.9 Local 3 4 5 6 7 0.1 0.1 0.2 0.2 0.2 N12 C28-N12 O28-N12 Brown Ln & Park Cir.12" PVC 156.6 Local 46 78 100 108 123 2.2 4.4 5 7 8 D2-N12 C30-N12 O30-N12 Brown Ln Inlet to Infiltration Tank 24" PVC 163.3 Local 49 83 106 114 130 2.3 4.4 5 7 8 J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.Road runoff 163.3 Local 0 1 10 13 15 0.0 0.8 3.2 3.8 3.7 P03-N16 OLET-P03-N16 WEIR03-N16 Centennial Apts. Underground Infiltration Tank 10'x80' Tank 163.9 -51 86 110 119 136 2.2 5 6 7 8 J18-N17 C36-N17 O36-N17 Park Cir.Road runoff 163.9 Local 51 87 120 132 150 2.2 5 6 9 11 N17 C61-N17 O61-N17 Gibson Ave Inlet 12" CMP 167.5 Local 62 104 141 155 176 2.3 5 7 9 12 OFALL-1 --Oklahoma Flats Outfall Outfall 172.8 -76 125 166 183 208 2.7 6 8 11 13 N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 15 24 28 32 37 0.4 1.2 1.6 2.0 2.3 N18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 9 15 18 20 23 0.3 0.8 1.1 1.4 1.6 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 23 38 46 52 60 0.7 2.0 2.6 3.4 4.0 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 33 54 65 73 84 1.0 2.9 3.8 5 6 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 33 54 65 73 84 1.0 2.9 3.8 5 6 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 33 53 65 73 84 1.0 2.9 3.8 5 6 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 33 53 64 73 84 1.0 2.9 3.8 5 6 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 32 53 64 73 84 1.0 2.8 3.8 5 6 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 14 21 25 27 31 0.6 1.2 1.6 1.8 2.1 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 14 21 24 27 31 0.6 1.2 1.6 1.8 2.0 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 14 21 24 27 31 0.6 1.2 1.6 1.8 2.0 N21 C49-N23 O49-N23 Neale Ave & Gibson Ave Confluence 36" CMP 21.8 Local 61 96 115 129 148 2.0 5 7 8 10 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 67 105 126 141 162 2.2 6 8 9 11 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 67 105 126 141 161 2.2 6 8 9 11 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 OFALL-2 --Neale Ave. Outfall Outfall 24.8 -67 105 126 141 161 2.2 6 8 9 11 N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 58 64 66 68 71 0.6 1.0 1.2 1.3 1.5 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -59 64 67 69 72 0.6 1.0 1.2 1.4 1.6 OFALL-3 --Smuggler Mine Outfall Outfall 5.6 -59 64 67 69 72 0.6 1.0 1.2 1.4 1.5 N22 C55-N24 -King St. (Flooding)Low Area; Flooding 1.7 Local 4 7 8 9 10 0.2 0.5 0.7 0.8 0.9 OFALL-4 --Bibbig Exemption Outfall Outfall 5.1 -13 19 23 25 29 0.4 0.8 1.1 1.2 1.4 *No WQCV is equal to the existing models output with no applied reduction in runoff flow rate or runoff volume. **Assumed pipe sizes. Oklahoma Flats Outfall Neale Avenue Storm System Smuggler Mine Outfall Bibbig Exemption Riverside Ditch Outfall Neale Ave. and OK Flats Basin 2-year WQCV Analysis 2-year Cumulative Runoff Volumes (1,000 gal)2-year Peak Flow Rates (cfs) Park Circle Tributary to Oklahoma Flats Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Conduit ID Overflow ID P97I. Table 2.13 WQCV Summary Table Page 2 of 3 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 0 1 1 1 1 0.0 0.0 0.0 0.0 0.0 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 0 1 1 1 1 0.0 0.0 0.0 0.0 0.0 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 0 1 1 1 1 0.0 0.0 0.0 0.0 0.0 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 -6 7 8 8 10 0.1 0.1 0.1 0.2 0.2 N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 2 2 3 3 3 0.0 0.1 0.1 0.1 0.1 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local 2 2 3 3 3 0.0 0.1 0.1 0.1 0.1 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local 2 2 3 3 3 0.0 0.1 0.1 0.1 0.1 N04 C16-N04 O16-N04 Silverlode Dr.12" CMP 9.1 Local 29 37 41 44 48 0.8 1.2 1.5 1.6 1.8 N11 C25-N04 -Silverlode Dr.Road runoff 0.7 Local 5 6 7 7 8 0.2 0.4 0.4 0.5 0.5 DW02-N04 OLET-DW02-N04 WEIR01-N04 Silverlode Dr. & Smuggler Mtn. Rd.Dry Well 9.1 Local 29 37 41 44 48 0.8 1.2 1.5 1.6 1.8 N10 C12-N10 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 12" CMP 90.0 Local 42 45 61 64 68 3.2 4.1 6 6 6 DW01-N10 OLET-DW01-N10 WEIR02-N10 Park Cir. & Smuggler Mtn Rd.Dry Well 90.0 Local 42 45 60 62 66 2.6 3.4 3.8 3.8 3.7 N13 C29-N13 O29-N13 End of Tributary at Brown Ln.12" PVC 95.7 Local 62 70 89 98 124 4.3 5 8 7 9 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -1 1 2 2 3 0.0 0.0 0.0 0.1 0.1 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 1 1 2 2 3 0.0 0.0 0.0 0.1 0.1 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 5 6 7 7 8 0.1 0.2 0.2 0.3 0.3 J20-12 C34-N12 -Free Silver Ct. roadside Ditch Ditch 60.9 -6 8 8 9 11 0.2 0.2 0.3 0.3 0.4 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local 6 8 8 9 11 0.2 0.2 0.3 0.3 0.4 D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 6 8 8 9 11 0.2 0.2 0.3 0.3 0.4 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.12" PVC 60.9 Local 6 8 8 9 11 0.2 0.2 0.3 0.3 0.4 N12 C28-N12 O28-N12 Brown Ln & Park Cir.12" PVC 156.6 Local 115 140 148 161 183 5 7 9 9 11 D2-N12 C30-N12 O30-N12 Brown Ln Inlet to Infiltration Tank 24" PVC 163.3 Local 121 147 155 167 185 5 7 8 8 8 J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.Road runoff 163.3 Local 8 9 30 35 53 2.1 2.9 6 6 7 P03-N16 OLET-P03-N16 WEIR03-N16 Centennial Apts. Underground Infiltration Tank 10'x80' Tank 163.9 -126 154 163 175 194 5 7 8 8 9 J18-N17 C36-N17 O36-N17 Park Cir.Road runoff 163.9 Local 135 163 193 210 248 6 7 11 13 15 N17 C61-N17 O61-N17 Gibson Ave Inlet 12" CMP 167.5 Local 158 192 225 244 286 7 8 13 14 16 OFALL-1 --Oklahoma Flats Outfall Outfall 172.8 -186 227 265 286 331 7 10 15 16 18 Neale Avenue Sto N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 33 42 46 50 55 1.2 1.9 2.5 2.8 3.1 N18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 20 26 29 31 35 0.8 1.4 1.8 2.0 2.2 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 53 68 75 81 89 2.1 3.3 4.2 5 5 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 74 95 106 115 126 3.0 5 6 7 8 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 74 95 106 115 126 3.0 5 6 7 8 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 74 95 106 114 126 3.0 5 6 7 8 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 74 95 106 114 126 3.0 5 6 7 8 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 74 95 106 114 126 3.0 5 6 7 8 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 28 35 38 41 45 1.2 1.9 2.2 2.4 2.6 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 28 35 38 41 45 1.2 1.9 2.2 2.4 2.6 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 28 35 38 41 45 1.2 1.9 2.2 2.4 2.6 N21 C49-N23 O49-N23 Neale Ave & Gibson Ave Confluence 36" CMP 21.8 Local 132 167 186 200 219 5 9 11 12 13 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 144 182 203 218 239 6 9 11 12 14 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 144 182 202 218 238 6 9 11 12 14 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 OFALL-2 --Neale Ave. Outfall Outfall 24.8 -144 182 202 218 238 6 9 11 12 14 N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 69 74 77 79 81 1.0 1.4 1.6 1.7 1.9 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -69 75 78 80 83 1.0 1.4 1.6 1.8 1.9 OFALL-3 --Smuggler Mine Outfall Outfall 5.6 -69 75 78 80 83 1.0 1.4 1.6 1.8 1.9 N22 C55-N24 -King St. (Flooding)Low Area; Flooding 1.7 Local 9 11 12 13 14 0.5 0.8 1.0 1.1 1.2 OFALL-4 --Bibbig Exemption Outfall Outfall 5.1 -26 32 35 38 41 0.8 1.3 1.5 1.7 1.9 *No WQCV is equal to the existing models output with no applied reduction in runoff flow rate or runoff volume. **Assumed pipe sizes. Park Circle Tributary to Oklahoma Flats Outfall Oklahoma Flats Outfall Neale Ave. and OK Flats Basin 5-year WQCV Analysis Smuggler Mine Outfall Bibbig Exemption Riverside Ditch Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Conduit ID Overflow ID 5-year Cumulative Runoff Volumes (1,000 gal)5-year Peak Flow Rates (cfs)P98I. Table 2.13 WQCV Summary Table Page 3 of 3 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV 100% WQCV 75% WQCV 50% WQCV 25% WQCV *No WQCV D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 1 1 1 2 2 0.0 0.0 0.0 0.1 0.1 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 1 1 1 2 2 0.0 0.0 0.0 0.1 0.1 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.1 0.1 N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 1 1 2 2 3 0.0 0.0 0.0 0.1 0.2 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 -7 12 18 22 22 0.1 0.3 0.4 0.5 0.6 N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 2 3 4 4 4 0.1 0.1 0.1 0.2 0.2 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local 2 3 4 4 4 0.1 0.1 0.1 0.2 0.2 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local 2 3 4 4 5 0.1 0.1 0.1 0.2 0.2 N04 C16-N04 O16-N04 Silverlode Dr.12" CMP 9.1 Local 37 45 51 55 59 1.1 1.6 1.9 2.1 2.4 N11 C25-N04 -Silverlode Dr.Road runoff 0.7 Local 6 7 8 8 9 0.3 0.5 0.5 0.6 0.7 DW02-N04 OLET-DW02-N04 WEIR01-N04 Silverlode Dr. & Smuggler Mtn. Rd.Dry Well 9.1 Local 37 45 51 55 59 1.1 1.6 1.9 2.1 2.4 N10 C12-N10 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 12" CMP 90.0 Local 50 65 71 80 80 5 5 6 6 6 DW01-N10 OLET-DW01-N10 WEIR02-N10 Park Cir. & Smuggler Mtn Rd.Dry Well 90.0 Local 50 64 68 76 75 3.9 3.8 3.9 3.8 3.7 N13 C29-N13 O29-N13 End of Tributary at Brown Ln.12" PVC 95.7 Local 70 103 98 115 140 5 8 9 9 9 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -1 4 7 9 9 0.0 0.1 0.2 0.3 0.3 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 1 4 7 9 9 0.0 0.1 0.2 0.3 0.3 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 6 7 8 9 9 0.2 0.2 0.3 0.3 0.4 J20-12 C34-N12 -Free Silver Ct. roadside Ditch Ditch 60.9 -8 12 15 17 18 0.2 0.4 0.5 0.6 0.6 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local 8 12 15 17 18 0.2 0.4 0.5 0.6 0.6 D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 8 12 15 17 18 0.2 0.4 0.5 0.6 0.6 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.12" PVC 60.9 Local 8 12 15 17 18 0.2 0.4 0.5 0.6 0.6 N12 C28-N12 O28-N12 Brown Ln & Park Cir.12" PVC 156.6 Local 138 164 167 181 207 6 9 10 12 13 D2-N12 C30-N12 O30-N12 Brown Ln Inlet to Infiltration Tank 24" PVC 163.3 Local 145 173 173 186 209 6 8 8 8 8 J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.Road runoff 163.3 Local 11 39 46 61 73 2.8 5 7 7 10 P03-N16 OLET-P03-N16 WEIR03-N16 Centennial Apts. Underground Infiltration Tank 10'x80' Tank 163.9 -152 182 182 195 219 6 9 9 9 9 J18-N17 C36-N17 O36-N17 Park Cir.Road runoff 163.9 Local 163 221 228 257 292 7 11 14 15 17 N17 C61-N17 O61-N17 Gibson Ave Inlet 12" CMP 167.5 Local 193 257 266 298 336 8 13 16 17 19 OFALL-1 --Oklahoma Flats Outfall Outfall 172.8 -228 300 313 349 390 10 14 18 20 22 N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 42 51 56 59 64 1.8 2.7 3.2 3.4 3.8 N18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 26 32 35 38 41 1.2 2.0 2.3 2.5 2.7 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 68 83 91 97 105 3.0 5 5 6 6.5 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 96 117 129 137 149 4.4 7 8 9 9 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 96 117 129 137 149 4.3 7 8 9 9 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 96 117 128 137 149 4.3 7 8 9 9 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 96 117 128 137 148 4.3 7 8 9 9 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 96 117 128 137 148 4.3 7 8 8 9 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 35 42 46 49 53 1.7 2.5 2.8 3.1 3.2 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 35 42 46 49 53 1.7 2.5 2.8 3.0 3.2 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 35 42 46 49 53 1.7 2.5 2.8 3.0 3.2 N21 C49-N23 O49-N23 Neale Ave & Gibson Ave Confluence 36" CMP 21.8 Local 169 204 224 239 259 8 12 13 15 16 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 184 223 244 261 282 8 13 14 16 17 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 184 223 244 261 282 8 12 14 16 17 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 OFALL-2 --Neale Ave. Outfall Outfall 24.8 -184 223 244 261 282 8 12 14 16 17 N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 74 79 82 85 87 1.3 1.7 1.9 2.1 2.2 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -75 81 84 87 90 1.3 1.7 2.0 2.2 2.3 OFALL-3 --Smuggler Mine Outfall Outfall 5.6 -75 81 84 87 90 1.3 1.7 2.0 2.2 2.3 N22 C55-N24 -King St. (Flooding)Low Area; Flooding 1.7 Local 11 13 15 16 17 0.8 1.1 1.2 1.3 1.4 OFALL-4 --Bibbig Exemption Outfall Outfall 5.1 -32 39 43 45 49 1.2 1.7 2.0 2.2 2.3 *No WQCV is equal to the existing models output with no applied reduction in runoff flow rate or runoff volume. **Assumed pipe sizes. Overflow ID Oklahoma Flats Outfall Neale Avenue Storm System Smuggler Mine Outfall Bibbig Exemption Riverside Ditch Outfall Neale Ave. and OK Flats Basin 10-year WQCV Analysis 10-year Cumulative Runoff Volumes (1,000 gal)10-year Peak Flow Rates (cfs) Park Circle Tributary to Oklahoma Flats Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Conduit ID P99I. P100I. 2-50 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 2.7.1.4 Riverside McSkimming Basin Existing System Description: The Riverside McSkimming Basin has a total drainage area of approximately 188.9 acres and mostly consists of medium-density residential property in the lower reaches. A large cemetery is located in the south, central edge of the basin. The upper headwaters become more sparsely developed traveling up Smuggler Mountain to open space areas. The Riverside McSkimming Basin consists of multiple flow paths through the widespread basin along the Roaring Fork River with major flow paths converging along Park Avenue, East Hopkins Avenue, East Cooper Avenue, and near Crystal Lake Road. East Cooper Avenue, a continuation of Highway 82, is the only flow path that currently has a storm system on its downstream end, consisting of 12-inch and 18-inch CMPs. A private retention pond (P01-R15) is located adjacent to the Salvation Ditch, just east of Crystal Lake Road which collects runoff solely from Sub-basin R15. It was estimated to have sufficient capacity to retain the 100-year event runoff volume. There are three additional aesthetic, private detention ponds located throughout the basin (P03-R08S, P04-R08N, and P02-R13), but these were modeled as initially full for each simulation, since any capacity to provide attenuation for storm runoff cannot be confirmed. Drainage Deficiencies: The majority of the Riverside McSkimming Basin lacks a storm system and flow generally is conveyed along streets, across parking lots, and through natural and landscaped swales. These areas were analyzed with the floodplain modeling criteria outlined in Section 2.6.5 and all areas were shown to have minimal flooding risk except for a known flooding area at the intersection of Midland Avenue and Park Avenue as well as an area near Regent Street to the south. A dry well (DW01-R07) at the corner of Midland Avenue and Park Avenue cannot handle the 2-year event and creates flooding in the area. A HEC-RAS model of this area along Park Avenue from Midland Avenue to outfall OFALL-04, including an overflow branch along Regent Street, was constructed to estimate the 100-year inundation area. Several private residences are impacted by the 100-year event along Regent Street and Park Avenue, close to OFALL-04. A single storm system located along the lower section of the East Cooper Avenue Outfall reach at R19 cannot handle the 5-year event. Another separate storm culvert located at R11 along Eastwood Drive is comprised of a single 12-inch CMP and cannot convey the 2-year event. 2.7.1.5 Eastwood Basin Existing System Description: The Eastwood Basin has a total drainage area of approximately 156.6 acres with the lower reaches covered with medium density residential property, which transitions to more sparsely populated towards Smuggler Mountain. The upper half of the basin remains undeveloped and is designated open space. The main flow path within the Eastwood Basin originates with runoff from the undeveloped upper reaches collecting along Mountain Laurel Drive. Storm runoff is routed along this rural road until it skirts the east side of the basin down natural swales through medium density residential property, parallel to West Lupine Drive. Drainage continues to Roaring Fork Drive and enters a grated storm inlet system just downstream of the Roaring Fork Drive and Highway 82 intersection at E02, where it is directed toward its outfall to the Roaring Fork River. P101 I. April 2015 2-51 | Stormwater Runoff and Drainage Facility Capacity Analysis A smaller, separate reach to the west collects flow from Sub-basin E05. The reach runs along the Highway 82 low point below a riprapped swale into another grated inlet where it is diverted across the highway towards the Roaring Fork River. Drainage Deficiencies: The upper area of the main outfall reach lacks any piped storm system and is conveyed along streets, street ditches, and natural swales through residential property to Highway 82. The 100-year flood inundation area was modeled along this main reach from junction J06-E02 to the outfall to the Roaring Fork River at OFALL-01. The 100-year flow path meanders and touches several residential structures between Mountain Laurel Drive and Roaring Fork Drive. Downstream of Roaring Fork Drive to the outfall, runoff is conveyed along the road alignment, crosses Highway 82 as shallow sheet flow and into the Roaring Fork River without compromising any additional structures. The downstream 18-inch, in-series cross culverts at Highway 82 along the main reach are unable to convey the 5-year event. The smaller drainage system at Highway 82, to the west that collects runoff from Sub-basin E05, was estimated to be able to convey the 10-year event. No known drainage deficiencies were reported for this basin. 2.7.1.6 Stillwater Bridge Basin Existing System Description: The Stillwater Bridge Basin is the largest and most undeveloped basin in the project area with a total drainage area of approximately 371.5 acres that extends beyond the city limits. The lower quarter of the basin is mostly medium density residential property with the remainder of the basin being undeveloped open space. Currently, there are no piped storm systems within the Stillwater Bridge Basin. All storm runoff is conveyed along residential streets and natural swales. The smaller, eastern drainage reach within the basin contains a private detention area upstream of East Lupine Drive. Large storm events are conveyed to this detention area which retains runoff up to the 50-year event. During the 100-year event, the pond attenuates the peak flow by reducing the peak inflow from 12 cfs to approximately 1 cfs. Overflow from the 100-year event spills across East Lupine Drive. Runoff then continues through residential property and down Highway 82 before crossing the highway to the Roaring Fork River. The larger Stillwater Bridge Basin drainage system collects runoff from natural drainage swales from the large upstream contributing sub-basins along Mountain Laurel Drive; then flowing through several residential properties before crossing Mountain Laurel Drive. The runoff then collects along West Lupine Drive where the final contributing area joins the system at the West Lupine Drive and Lupine Drive intersection. The resulting total runoff continues down along Lupine Drive where it crosses over Highway 82 to a large residential property driveway, spreads to the southeast, and eventually outfalls to the Roaring Fork River. Drainage Deficiencies: The entire Stillwater Bridge Basin lacks any piped stormwater conveyance and results in the largest runoff peak flows although no drainage deficiencies have been reported in the area. The basin relies on residential streets and road side swales to convey flow. The main, larger reach to the west convenes at West Lupine Drive and Lupine Drive, creating large peak runoff flows (over 40 cfs) that exceed the street capacity along Lupine Drive. Thereby adjacent properties to the west and across Highway 82 flood as flow makes its way toward the Roaring Fork River. A HEC-RAS model was developed to estimate the 100-year inundation area along this entire reach from Mountain laurel Drive to the outfall to the Roaring Fork River at OFALL-2. A smaller branch to the reach (which collects runoff from Sub-basin P102 I. 2-52 | Stormwater Runoff and Drainage Facility Capacity Analysis April 2015 S05) was also modeled as part of the main reach. The inundation area along the smaller branch impacts two residences before joining at InfoSWMM junction S08. The main reach inundation area impacts three additional residences before being contained in the street section along West Lupine Drive to Lupine Drive. Flow then spreads out of the street into a private residence before Highway 82. After flow crosses Highway 82 as shallow concentrated flow, the 100-year flooding spreads around a residence adjacent to the Roaring Fork River where flow pools in the driveway, overflows around the house to the east and spreads out along a field before flowing into the Roaring Fork River (see Figure 2.7). A smaller branch of the main reach in the Stillwater Bridge Basin, which collects flow from Sub- basins S03 and S06, was analyzed with the criteria in Section 2.6.5 and deemed a low flooding hazard due to the low flows and shallow flow depths. The smaller flow reach to the east was also modeled in HEC-RAS to determine the 100-year flood inundation area. Flow collected from Sub-basin S04 meanders through private property alongside a residence before reaching East Lupine Drive. Runoff then flows into the private detention pond. Flow then spills over East Lupine Drive, spreads to shallow sheet flow, which compromises another private residence, before collecting along Highway 82 and flows to the south. The flooding limits then spreads as shallow sheet flow over Highway 82 and spreads across an undeveloped field before discharging to the Roaring Fork River at OFALL-1. 2.8 DISCUSSION Apart from the Gibson Avenue Basin and Neale Avenue and OK Flats Basin, most of the drainage areas evaluated do not have any piped storm systems. Instead, stormwater and snowmelt runoff is conveyed by the existing streets, road side ditches and natural swales. This is true in the Stillwater Bridge Basin, Eastwood Basin, and the Riverside McSkimming Basin, where some of the highest peak flows were estimated. Of the evaluated storm sewer systems that do exist and were surveyed, most were estimated to be able to convey the 5-year event which meets Aspen’s current standards. The Neale Avenue & OK Flats, Eastwood, and Stillwater Bridge Basins were shown to have the largest 100-year inundation areas with multiple residences affected. There are a number of private, aesthetic detention ponds located throughout the Study Area but only one in the Stillwater Bridge Basin that was modeled with any storage to attenuate storm peak runoff flows. That location was estimated to fully retain the 50-year event runoff volume. Two retention areas, one downstream of the Smuggler Mine in the Neale Avenue and OK Flats Basin and one in the southeast corner of the Riverside McSkimming Basin, were found to retain the 100-year runoff volume for their respective contributing areas. An engineered, underground infiltration basin in the upper reaches of the Gibson Avenue was evaluated and estimated to be able to substantially attenuate all frequency storms. A separate private underground detention tank in at the upstream end of the flooded Park Circle street in the Neale Avenue and OK Flats Basin was also evaluated and shown to be inadequately sized for the 2-year event. All dry wells that were surveyed and evaluated in this study were found to be inadequate for the 2-year runoff volume and did not attenuate any peak flows for any return period. P103 I. April 2015 2-53 | Stormwater Runoff and Drainage Facility Capacity Analysis This page intentionally left blank P104 I. SECTION THREE MUDFLOW ANALYSIS April 2015 3-1 | Mudflow Analysis 3 Section 3 THREE Mudflow Analysis 3.1 SCOPE OF WORK This section discusses and analyses the potential hazards from mud floods and mudflows that may develop in the watershed from rainfall events. The work scope of the mudflow analysis is to: 1. Obtain and review current available information and data, including previous debris-flow studies for Aspen. A field investigation was performed to identify critical watersheds that could develop potential mudflow, based on site-specific land cover, top soils/rock conditions, and slope stability. 2. Estimate the magnitude of potential debris-flow events originating from the critical watersheds by creating a detailed 2-D mudflow model. The 2-, 10-, 50-, and 100‐year storm flow hydrographs were obtained from the CUHP model outputs in this study and were used to produce the mudflow in a FLO-2D model. The 2008 2-foot contours were used to generate the topographic basis for a FLO-2D model. The downstream limit of the 2-D hydraulic model will be along the Roaring Fork River. 3. Delineate the approximate extent of the debris-flow hazard area and potential mudflow depths along the flow paths and the historical alluvial fan within the Study Area. 4. Describe the methods, assumptions, and the results of the mudflow analysis. 3.2 RELEVANT STUDIES AND MATERIAL Previous study reports and information provided by Aspen or obtained directly from other sources by URS were reviewed. In addition, related information and studies along the Roaring Fork River were also considered. Specific documents and data that were considered include the following: • Drainage Facility Capacity Analysis of the City of Aspen, Colorado. WRC Engineering, Inc. 1998. (Reference 63) • Surface Drainage Master Plan for the City of Aspen, Colorado. WRC Engineering, Inc. 2001. (Reference 64) • Geomorphic, sedimentologic, hydraulic and sediment-continuity reports prepared by Mussetter Engineering, Inc. for the San Miguel River (Reference 27) and Cornet Creek (Reference 26). • Field Notes dated May 2008: A mud slide occurred on the uphill slope at the end of North Spruce Street and generated mudflow to the downstream adjacent properties. The pictures of mud slide were obtained from the City and are shown in Figure 3.1. These indicate active unstable slopes and hazard areas in the watershed. P105 I. 3-2 | Mudflow Analysis April 2015 A. Mud Slide at Uphill Slope B. Debris/Mud Deposition on North Spruce Street Figure 3.1. Mud Slide, May 8, 2008 3.3 CHARACTERISTICS OF MUDFLOW AND MUD FLOOD For the purposes of this study, the National Research Council (NRC) (1982) terminology for describing mudflows and other forms of hyperconcentrated flows has been adopted. Hyperconcentrated sediment flows (mudflows and mud floods) are part of a continuum in the “physics of flowing water and sediment movement that ranges from clear water flow to mass wasting processes (landslides)” (SLA and O’Brien, 1989). In general, sediment transport characteristics range from suspended and bed load transport in water floods to mass wasting in landslide events. Suspended and bed load transport mean sediment particles are mainly carried by running water and travel along stream paths. Landslide is a downward and outward movement of unconsolidated material caused by gravity. Generally, movement of materials stops at the toe of the downhill slope. The NRC Committee (NRC, 1982) proposed four categories to delineate the continuum of types of sediment transport: water floods, mud-floods, mudflows, and landslides, as shown in Figure 3.2. The bounds of each of these categories can be approximated based on the fluid properties and in particular by the sediment concentration (by volume) of the fluid as shown in Table 3.1. The sediment concentration of fluid is defined as the ratio of the sediment volume to the total volume and is given by: ܥ௩ ൌ ௏ೞ ௏ೢ ା௏ೞ P106 I. April 2015 3-3 | Mudflow Analysis where Cv = sediment concentration by volume, Vs = volume of sediment, and Vw = volume of clear water. Figure 3.2. Hyperconcentrated Sediment Flow Classification (after National Research Council 1982) This study focuses on the sediment transport characteristics of the mud flood and mudflow categories. Table 3.1 provides brief descriptions of the sediment transport characteristics for each mudflow category. Mudflows are typically non-Newtonian, very viscous and hyperconcentrated sediment flows, whose fluid properties change dramatically as they flow down alluvial fans or steep channels. The behavior of the mudflow is a function of the fluid matrix properties (i.e. density, viscosity, and yield stress), channel geometry, slope, and roughness. Viscosity is in turn a function of the type of sediment (clay or silt), the sediment concentration, and the water temperature. Mudflows have high sediment concentrations and high yield stresses, which may produce laminar flow. Large flood events, such as the 100-year flood, may contain too much water to produce a viscous mudflow event. Per Section 7.0 of the URMP (Reference 1), higher recurrence interval rainfall events such as the 10- or 25-year return period storm may have a greater propensity to create viscous mudflows with high viscosity and yield stress. Usually, the peak concentration of sediment during a P107 I. 3-4 | Mudflow Analysis April 2015 mudflow event is about 45% by volume, and the average sediment concentration is between 20% and 35% by volume. Mud floods will be produced by larger flood events such as the 50- or 100- year flood. Since mud floods contain a higher proportion of water than mudflows, mud floods are less viscous and are always turbulent. Table 3.1 Mudflow Behavior as a Function of Sediment Concentration Sediment Concentration Flow Characteristics by Volume by Weight Landslide 0.65-0.80 0.83-0.91 Will not flow; failure by block sliding 0.55-0.65 0.76-0.83 Block sliding failure with internal deformation during the slide; slow creep prior to failure Mudflow 0.48-0.55 0.72-0.76 Flow evident; slow creep sustained mudflow; plastic deformation under its own weight; cohesive; will not spread on level surface 0.45-0.48 0.69-0.72 Flow spreading on level surface; cohesive flow; some mixing Mud Flood 0.40-0.45 0.65-0.69 Flow mixes easily; shows fluid properties on deformation; spreads on horizontal surface but maintains an inclined fluid surface; large particle (boulder) settling; waves appear but dissipate rapidly 0.35-0.40 0.59-0.65 Marked settling of gravels and cobbles; spreading nearly complete on horizontal surface; liquid surface with two fluid phases appears; waves travel on surface 0.30-0.35 0.54-0.59 Separation of water on surface; waves travel easily; most sand and gravel has settled out and moves as bedload 0.20-0.30 0.41-0.54 Distinct wave action; fluid surface; all particles resting on bed in quiescent fluid condition Water Flood <0.20 <0.41 Water flood with conventional suspended load and bedload Notes: See FLO-2D Reference Manual for the references. According to the previous studies and Chapter 7 – Mudflow Analysis of the URMP, hyperconcentrated flows are categorized as mudflows emanating from smaller precipitation events (2- and 10-year events) and are categorized as mud floods emanating from larger precipitation events (50- and 100-year events). 3.4 SITE INVESTIGATION AND CRITICAL WATERSHED IDENTIFICATION A field investigation for the mudflow analysis was conducted on October 9 and 10, 2012. For this project, the study area is divided into six major basins. Field conditions of each watershed were observed, including land covers, topsoils/rocks, overland slope, surface erosion or soil loss locations, and flow paths. The field photographs shown in Figure 3.3 briefly explain the P108 I. April 2015 3-5 | Mudflow Analysis existing watershed conditions and were used as the reference material for identifying the critical watersheds which would potentially produce mudflows during precipitation events. In addition, the potential geologic hazard map on Smuggler Mountain above Aspen obtained from the USGS and shown in the 2001 Surface Drainage Master Plan for the City of Aspen (Reference 64), shown in Figure 3.4, was referenced to identify the unstable areas within the study watersheds (i.e. alluvial fans, landslide areas, rock fall areas, and other unstable slopes). Alluvial fans identified in the areas are generally indicative of past and potential mudflow events in the watersheds. This field information and evaluation criteria were used to identify the critical watersheds for the mudflow hazard analysis. The existing conditions, historical mudflow records and identification are described for each watershed below. In this study, a critical watershed for mudflow hazard was identified by the observed or documented mudflow evident in the watershed and a significant portion of the watershed labeled as Potential Unstable Slopes in the USGS Geological Survey Map (Figure 3.4). A quasi-stable watershed for mudflow hazard was identified by no mudflow observed or documented, and well- vegetated surfaces in the watershed, but a portion of the watershed labeled as Potential Unstable Slopes in the USGS Geological Survey Map. 3.4.1 Hunter Creek Basin Approximately 55% of the watershed is undeveloped and located at the uphill area east of the end of Spruce Street. Half of the undeveloped area is labeled as Potential Unstable Slopes in the USGS Geological Survey Map (Figure 3.4). The existing residential properties were mainly built on historical alluvial fans. Photograph No. 4 in Figure 3.3 shows that the current hill slope is covered by grass, shrubs, and bare topsoil. In addition, a mud slide and associated mudflow were observed along Spruce Street in May 2008 (Figure 3.1). These observations indicate that the Hunter Creek Basin is classified as a critical watershed for mudflow hazard. 3.4.2 Gibson Avenue Basin Approximately 29% of the watershed is undeveloped and located at the uphill area east of Silverlode Drive. The undeveloped area is mostly labeled as Potential Unstable Slopes in the USGS Geological Survey Map. The existing residential properties were mainly built at the toes of the slopes and on historical alluvial fans. Photograph No. 7 in Figure 3.3 is a street view of Silverlode Drive. No historical remains of mudflow such as debris flow stains or damages were seen on buildings and trees, and no sand and silt depositions, were observed from the field investigation. However, from conversations with local residents during field reconnaissance, the URS Team learned that mudflow damage occurred at the condominium properties near Free Silver Court. The current hill slope above the retaining wall on Free Silver Drive is covered by grass, shrubs, and oak. These observations indicate that the Gibson Avenue Basin is classified as a critical watershed for mudflow hazard. 3.4.3 Neale Avenue and OK Flats Basin Approximately 70% of the watershed is undeveloped and located at the uphill area east of Silverlode Drive and Sesame Street. Mud slide remains were observed at the north part of the watershed near Smuggler Mountain Road. Photograph Nos. 2, 3, and 5 in Figure 3.3 show the obvious wide surface erosion areas covered by loose sandy soils and piping erosion on the slope. A bare soil area is exposed in the Smuggler Mine site just east of Silverlode Drive and north of P109 I. 3-6 | Mudflow Analysis April 2015 Smuggler Mountain Road (Photograph No. 1 in Figure 3.3). These areas could potentially initiate mudflows during a rain event. A potential hazard area of about 42 acres is labeled as Potential Unstable Slopes in the USGS Geological Survey Map (Figure 3.4). The location agrees with the erosion areas observed in the field. The existing residential properties were mainly built at the toes of the slopes and on historical alluvial fans. The current hill slope is covered by bare soil, grass, shrubs, oaks, and aspens. These observations indicate that Neale Avenue and OK Flats Basin is classified as a critical watershed for mudflow hazard. 3.4.4 Riverside McSkimming Basin About 38% of the watershed is undeveloped and located in the uphill area in the northeastern portion of the watershed. An area of approximately seven acres is labeled as Potential Unstable Slopes in the USGS Geological Survey Map (Figure 3.4). Photograph Nos. 8 and 9 in Figure 3.3 show the existing slope conditions. The existing hill slope is a wide and flat surface covered by grass, weeds and short bushes. No visible open channels or erosion gullies were found on the slope. No historical remains of mudflow were observed during the field investigation. These indicate that no concentrated flow was present in the past that could result in mudflows. The current hill slope is well-covered by bare rock/granite, grass, shrubs, aspen, and oak. These observations indicate that the watershed of Riverside McSkimming Basin is classified as a quasi- stable watershed for mudflow hazard. 3.4.5 Eastwood Basin Approximately 64% of the watershed is undeveloped and located in the uphill area northeast of Mountain Laurel Drive. Only a small area is labeled as Potential Unstable Slopes in the USGS Geological Survey Map (Figure 3.4). No visible open channels were found on the slope and no historical remains of mudflow hazard were observed from the field investigation. These indicate that concentrated floods and mudflow might not have occurred in the past in this area. The current hill slope is well-covered by bare rock/granite, grass, shrubs, aspen, and oak. These observations indicate that the Eastwood Basin is classified as a quasi-stable watershed for mudflow hazard. 3.4.6 Stillwater Bridge Basin Approximately 90% of the watershed is undeveloped and located at the uphill area northeast of Mountain Laurel Drive. A mountain arroyo runs between the properties of 711 Mountain Laurel Drive and 681 Mountain Laurel Drive and then disappears downstream from Mountain Laurel Drive. Photograph No. 6 in Figure 3.3 shows a high-density coniferous forest and vegetation located on the upper hill slopes. The lower hill slopes are well-covered by coniferous forest and aspen. No historical remains of mudflow hazard were observed from the field investigation. In addition, the state geological map shows that the geologic unit in this watershed is mainly granite. These observations indicate that the Stillwater Bridge Basin is classified as a quasi- stable watershed for mudflow hazard. P110 I. !!!!!!! !!!!!!!!!!!!!! !! ! !! ! ! ! ! ! ! ! ! ! Hunter Creek Basin "Hunter Creek Basin Neale Avenue and OK Flats Basin Riverside McSkimming Basin Gibson Avenue Basin Eastwood Basin Stillwater Bridge Basin RoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENAST" 2 " 2 " 2 ¬«9 ¬«8 ¬«7 ¬«6 ¬«4 ¬«2 ¬«1 ¬«12 ¬«11 ¬«10 8100 9000910092009300940095009600970098008000 10300104007900 102001 0 1 0 010000 8 7 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001020082008600 8100 8900 8300 9 9 0 0 9000860089008000101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010 0 0 0 840080008000870080008500 950085008800¬«5 ¬«3 0 1,000 Feeto Site Investigation and Critical Watersheds Smuggler/Hunter Surface Drainage Master Plan 3.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-03 Site Investigationr90.mxd Plot Date: 1/9/2015 Legend !!Irrigation Ditch, Culvert Irrigation Ditch, Open Major Basins Topographic Contour (feet NGVD29) Potential Geologic Hazards* Alluvial Fans Flood Plains Potential Unstable Slopes 10 12 11 8 9 7 1 4 6 35 2 * Source: U.S. Geological Survey (WRC Engineering Inc., 2001)P111I. !!!!!!! !!!!!!!!!!!!!! !! Hunter Creek Basin "Hunter Creek Basin Neale Avenue and OK Flats Basin Gibson Avenue Basin Riverside McSkimming Basin Eastwood Basin Stillwater Bridge Basin RoaringForkRiver Hallam Lake H u n te rC re e k RiversideDitchAstorMocklin Salvation Sal vat i onUTEAVEEMAINST ECOOPERAVE EHOPKINSAVE GI BSONAVEEDURANTAVE WFRANCISST SPRUCESTNMILLSTPARKCIRWHALLAMST N1STSTPARKAVEDEANST ELUPI NEDRMTNLAURELDRLAKEAVESASPENSTSORIGINALSTSMONARCHSTOAKLNLONEPINERD SHUNTERSTSWESTENDSTVINE ST NEALEAVENSPRINGSTUTEPLSHADYLNSMILLSTS1STSTEHYMANAVE EASTWOOD DR KINGST EBLEEKERST SGALENASTWESTVIEW DR RIO GRANDE PL WATERSAVE NORTHSTARDRMAPLELNSGARMISCHSTSALPSRDASPENMTNRDRACESTS K IM M IN G L NSESAMESTARDMOREDREHALLAMST WLUPI NEDRAJAXAVEBROWNLNNORTHWAYDRSTILLWATERDRR I V E R S I D E D RSRIVERSIDEAVEWILLIAMSWAY CRYSTAL LAKE RDCOTTONWOODLNPEARLCT FABILOOP MTNLAURELCTMASCOTTELN ALICELNSSPRINGSTSSPRINGSTSGALENAST8100 90009100920093009 40 0 95009600970098008000 10300104007900 102001 0 1 0 010000 87 0 0 8600 105009900 8500 8300 8400 8200 8 8 0 0 106008 9 0 0 7800 8400 910081001030010200820086008100 8900 8300 9 9 0 0 90008600890080001 0 3 0 0 101009 6 0 08300 9 7 0 0 7900 9 6 0 08600950010100100008200 9 8 0 0 8000 9100920010000840080008000870080008500 9500850088000 1,000 Feet o Potential Geologic Hazards Smuggler/Hunter Surface Drainage Master Plan 3.4 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-04 Geologic Hazardsr90.mxd Plot Date: 1/9/2015 Legend !!Irrigation Ditch, Culvert Irrigation Ditch, Open Major Basins Topographic Contour (feet NGVD29) Potential Geologic Hazards* Alluvial Fans Flood Plains Potential Unstable Slopes Geologic Unit (USGS 1:500K) Glacial Drift Granite Gravel Limestone Shale * Source: U.S. Geological Survey (WRC Engineering Inc., 2001)P112I. April 2015 3-9 | Mudflow Analysis 3.4.7 Summary In summary, three critical watersheds were identified for potential mudflow hazards and were analyzed using FLO-2D in this study – the Hunter Creek Basin, the Gibson Avenue Basin, and the Neale Avenue and OK Flats Basin,. As described above, the remaining watersheds were deemed quasi-stable based on field observations, vegetative cover, and with presence of only small areas of unstable slopes. Those watersheds do not warrant FLO-2D analysis. 3.5 FLO-2D 3.5.1 Introduction FLO-2D is a quasi-two-dimensional, finite difference flood routing model. The model utilizes a volume conservation scheme to simulate both subcritical and super-critical flows. Overland flow is modeled using a 2-D diffusive wave approximation of the momentum equation. A central difference routing scheme with eight potential flow directions is used to simulate the progression of the floodwave hydrograph over a system of square grids. In addition to modeling water-only flow, the program can also model hyperconcentrated sediment flow or mudflow. Hyperconcentrated sediment flow is runoff that contains a very high concentration of sediment. FLO-2D requires a representation of the topography of the study area. This is accomplished by establishing a network of nodes and assigning x-y coordinates and elevations to each node. A typical grid node spacing is 200 feet to 500 feet. Decreasing the node spacing increases the number of nodes and decreases the length of time step used in the model. Both factors increase the model’s run time. In this study, a fine grid size, 30 feet, was used. The FLO-2D model contains several components that are used to represent and model the complex topography and processes, including: channel-floodplain flow exchange, loss of storage due to buildings, flow obstructions, simulation of hydraulic structures, simulation of street flow and simulation of hyper-concentrated sediment flows (mudflows). Flow in a FLO-2D model can be generated by inputting a runoff hydrograph at select nodes. Hyperconcentrated sediment flow is simulated by the FLO-2D model using a quadratic rheological model that includes viscous stress, yield stress, turbulence and dispersive stress terms as a function of sediment concentration. FLO-2D does not have the ability to model unsteady phenomena such as surging. It also assumes a rigid boundary, and therefore, does not model aggradation or scour. The governing equations used in FLO-2D to route water flow and/or hyperconcentrated sediment flow include the numerical integration of the continuity equation and the dynamic wave equation as shown in the FLO-2D User’s Manual (Reference 17). In a FLO-2D model, flow depth, velocities, and discharges between adjacent nodes are calculated every time step. The model makes a single sweep of the grid system, explicitly solving for flow depth one node at a time for each time step, and storage volumes at each node for both water and sediment are computed. The inflow, outflow, and change in storage across the entire grid system are assessed at the end of each time step to ensure that volume is conserved within tolerance levels. If the volume is not conserved sufficiently, the model will automatically reduce the time step and re-solve for flow depth at each node. In this study, mud floods and mudflows were modeled using inflow hydrographs obtained from the InfoSWMM model presented in Section 2. FLO-2D routes the hyperconcentrated flows, tracking the sediment volumes through the system. Changing sediment concentration and dilution effects are simulated at each node by the FLO-2D program. Sediment concentration P113 I. 3-10 | Mudflow Analysis April 2015 governs the movement of the fluid matrix. Quadratic rheological equations are used to predict viscous and yield stresses as a function of sediment concentration. Simulation outputs generated by the FLO-2D model include maximum mudflow depths and velocities, and a summary of the total inflow, outflow, storage, and losses within the study area. 3.5.2 Methodology and Assumptions The CUHP basin hydrology models were first run to estimate runoff hydrographs for clear water only. These outflow hydrographs at the critical outfall locations, along with the estimated sediment concentrations at each time step, were imported into the inflow nodes on the upstream arroyos above the residential areas in the FLO-2D models. The peak sediment concentration by volume corresponds to the peak of the clear-water flow hydrograph. Hydraulic structures such as bridges and culverts were assumed to be blocked in the FLO-2D models. The existing storm drainage system only covers a very limited area within the City, and a majority is located at the downstream end area of each drainage basin close to the Roaring Fork River. Therefore, the local inlets and grates were conservatively assumed to be clogged by sediment or debris during mudflow events. Since the surface runoff hydrographs were obtained from the CUHP model outputs, there are no additional losses due to infiltration and initial rainfall abstractions in the FLO-2D model. Determination of the recurrence interval of hyperconcentrated sediment flow events is difficult due to the complex relationships between rainfall, antecedent soil moisture conditions and availability of sediment. Antecedent moisture conditions can influence whether a mudflow event will occur for a given rainfall event. For example, a 25-year rainfall event may initiate a mudflow if the soils are saturated, whereas the same 25-year rainfall event may not initiate a mudflow if the soils are not saturated. Antecedent moisture conditions can also effect soil erosion, bank and slope stability, and the magnitude and timing of runoff. In addition, the availability of stored sediment in the basin affects the magnitude and characteristic of the hyper- concentrated sediment flow. The time elapsed since the last major storm event also affects the quantity of sediment stored in the channel and watershed, which could increase the mudflow potential during the next storm event. In this study, the frequency of a mudflow was assumed to be equal to the frequency of the rainfall. The hypothetical two-hour frequency rainfall events were used as the standard storms to generate the runoff hydrographs for the mudflow simulations. The outputs from the FLO-2D modeling are limited by the assumptions or inputs such as rainfall distribution, sediment concentration, topographic accuracy, etc. The results only present the potential and magnitude of mud floods and mudflows that may develop due to rainfall events in the study area. 3.5.3 Input Data for FLO-2D Models Mudflow simulations were conducted for 2-, 10-, 50-, and 100-year frequency storm events for this study. The model inputs include topographic data, inflow hydrographs with sediment concentration conveyed by the flow, and Manning’s friction coefficient along the flow paths. The input data that affects the results of the modeling effort the most are described below. P114 I. April 2015 3-11 | Mudflow Analysis 3.5.3.1 Elevation Data and Grid Size The FLO-2D topographic surface was generated from the 2008 Aspen/Pitkin County Airport (ASE) 2-foot contours. For this study, 9,574 cells were created at a spacing of 30 feet. A grid size of 30 feet was assumed to adequately resolve the topography, yet limit the total number of cells so each computer run would be completed in a reasonable time. It should be noted that topographic surfaces often do not adequately resolve roadway embankments, stream crossings and areas of recent development. Therefore, the flood routing results may not provide adequate detail at these features. In addition, in the FLO-2D topographic surface, the existing Smuggler Mine on-site pond was filled up to the existing ground elevation. This results in a slightly more conservative inundation extents and mudflow hazard mapping. 3.5.3.2 Buildings and Streets Buildings were identified using the GIS data and the 2008 aerial image and incorporated into the analysis as a GIS dataset. Building heights were added to the ground elevation so no flow was allowed to pass through the buildings. Major roads and streets were specified and modeled as flood conveyance features. A global street width of 20 feet and curb height of 0.5 feet were assigned to the street elements in the FLO-2D models. 3.5.3.3 Overland Flow Manning’s n Roughness Coefficient The routed overland flow travels over floodplains or historical alluvial fans which are fully developed with buildings, landscapes, and public infrastructure. Overland flow velocities and depths vary with topography and the surface roughness. Typical Manning’s “n” roughness coefficients for overland flow are shown in Table 3.2. According to the existing site conditions, a global Manning’s n-value of 0.05 was applied to the entire model besides street elements. In the FLO-2D model, the floodplain roughness will be increased when the flow depth decreases to below 0.2 ft. This roughness adjustment will slow the downstream progression of the floodwave. For this study, the floodplain Manning’s n-values vary from 0.05 up to 0.2 depending on the computed flow depth. For streets, a global n-value of 0.02 was used. Table 3.2 Overland Flow Manning’s Roughness Values1 Surface N-Value Dense Turf 0.17-0.80 Bermuda and dense grass, dense vegetation 0.17-0.48 Shurbs and forest litter, pasture 0.30-0.40 Average grass cover 0.20-0.40 Poor grass cover on rough surface 0.20-0.30 Short prairie grass 0.10-0.20 Sparse vegetation 0.05-0.13 Sparse Rangeland 0% cover 0.09-0.34 P115 I. 3-12 | Mudflow Analysis April 2015 Table 3.2 Overland Flow Manning’s Roughness Values1 Surface N-Value 20% cover 0.05-0.25 Plowed or tilled fields Fallow – no residue Conventional tillage Chisel plow Fall disking No till – no residue No till (20-40% residue cover) No till (60-100% residue cover) 0.008-0.012 0.06-0.22 0.06-0.16 0.30-0.50 0.04-0.10 0.07-0.17 0.17-0.47 Open ground with debris 0.10-0.20 Shallow flow on asphalt or concrete (0.25” to 1.0”) 0.10-0.15 Fallow fields 0.08-0.12 Open ground, no debris 0.04-0.10 Asphalt or concrete 0.02-0.05 Notes: 1Adapted from COE, HEC-1 Manual, 1990 and the COE, Technical Engineering and Design Guide, No. 19, 1997 with modifications. 3.5.3.4 Outflow Boundary Conditions To discharge flows from the grid system in the FLO-2D model, outflow cells must be specified. The outflow boundary for this project area is continuous along the Roaring Fork River and up Hunter Creek. The model calculates outflows using the free flow method. 3.5.3.5 Numerical Routing Setup The following computational tolerance values were selected for the FLO-2D model for the Study Area: • Floodplain Limiting Froude Number = 2.0 • Tolerance value for the percent change (DEPTOL) = 0.2 • Surface detention value (TOL) = 0.1 foot • Maximum value of the numerical stability coefficient for full dynamic wave flood routing (WAVEMAX) = 1.0 • Dynamic wave stability coefficient = 0.1 The simulation time is 48 hours, which is much longer than the inflow hydrograph duration (about 2 hours). This allows the simulated flood peaks to pass through the entire study area unless the entire flood volume is captured in the storage areas in the watershed. P116 I. April 2015 3-13 | Mudflow Analysis 3.5.4 Modeling Scenarios Based on the scope of work for this study, four scenarios were modeled, namely: • Scenario I: Mudflow from the 2-year rainfall event • Scenario II: Mudflow from the 10-year rainfall event • Scenario III: Mud flood from the 50-year rainfall event • Scenario IV: Mud flood from the 100-year rainfall event 3.5.5 Mudflow Hydrographs and Initiation Locations Mudflow was assumed to be initiated on the upstream arroyos within each critical watershed. Six sub-basins were subsequently identified as the potential mudflow hazard sources that produce mudflow to the downstream watershed areas. They are Sub-basins H01, G01, G02, G04, N01 and N04, and N02. The clear water outflow hydrographs from these basins were obtained from the CUHP model outputs. These clear-water inflow hydrographs are input to the FLO-2D model at the specified elements near the head of the flowpath in the study watersheds. The inflow cells in the FLO-2D model are shown in Figure 3.5. Figure 3.5. Locations of the Inflow Cells in the FLO-2D Models The clear-water hydrograph is bulked with an estimated sediment concentration (by volume, Cv) to represent the mudflow hydrograph. The total volume of the water and sediment in a mudflow can be determined by multiplying the clear-water volume by the bulking factor, where the bulking factor, BF, is defined by: P117 I. 3-14 | Mudflow Analysis April 2015 𝐵𝐵=1(1 −𝐶𝑣) For example, a sediment concentration of 10 % (Cv =0.10) creates a bulking factor of 1.11, indicating the flood volume is 11 percent greater than if the flood was considered to be only water. For this study, the maximum bulking factors are about 1.8 and 1.5 for mudflow and mud flood events, respectively. The sediment concentrations during a flood hydrograph vary with flow discharges and were estimated based on Aspen’s criteria, previous studies, and recommendations provided in the FLO-2D manual. The developed sediment concentration hydrographs are included in Appendix C and have the following characteristics: 1. The peak sediment concentration during a mudflow event from the 2- and 10-year storm events was assumed to be 45%, and associated average sediment concentration was 35%, according to Aspen’s criteria. For a mud flood event from the 50- and 100-year storm events, the peak concentration of sediment was assumed to be 35%, and associated average sediment concentration was 25%. 2. Sediment transport capacity of clear water can be expressed as a power function of flow discharge. Cv−clear water =a ∙𝑄𝑤𝑤𝑤𝑤𝑤𝑏 where Cv-clear water = clear-water sediment transport capacity in concentration by volume, Qwater = clear-water discharge, and a and b = empirical coefficients of a power function. The power function resulted in maximum sediment concentration at the peak discharge of a hydrograph. The empirical coefficients a and b were determined by trial-and-error so the predicted maximum sediment concentration would equal either 45% or 35% and the predicted average sediment concentration would equal either 35% or 25%, for mudflow or mud flood, respectively, as described above. 3. The dynamic viscosity, η, and yield stress, τy, of mudflow were estimated based on O’Brien’s 1986 study (References 31 and 32). Table 3.3 shows the summary of power functions and corresponding coefficients and exponents from O’Brien’s study. The parameter values of Aspen Watershed were adopted and used for the FLO-2D mudflow modeling in this study. P118 I. April 2015 3-15 | Mudflow Analysis Table 3.3 Yield Stress and Viscosity as a Function of Sediment Concentration* 3.6 FLO-2D MODELING RESULTS Summary outputs from the FLO-2D model runs for all scenarios were provided in Appendix C. The FLO-2D post processor program, Mapper Pro, was used to generate the computed maximum mudflow depth and inundation area that were used in creating the inundation maps. Figures 3.6 through 3.9 depict the mudflow inundation areas and depths resulting from the FLO-2D modeling under the four scenarios. These simulated results present the potential mudflow hazard under the existing conditions with the frequency-precipitation events. 3.6.1 2-Year Mudflow Event The flow velocity at the end of model run (48 hours) is about zero feet per second. This indicates that the 2-year mudflow will be captured in the depression areas within the drainage system and limited areas will be impacted. About six residential buildings would be impacted by the mudflow with a flood depth less than one foot. The potential mudflow produced from the Smuggler Mine site would be captured and stored on the mine site. P119 I. 3-16 | Mudflow Analysis April 2015 3.6.2 10-Year Mudflow Event The flow velocity at the end of the model run is about zero feet per second. This indicates that the 10-year mudflow will be captured in the depression areas within the watershed and limited areas will be impacted. The potential mudflow hazard areas are the neighborhoods and communities close to Silverlode Drive, and upper Spruce Street, and the Smuggler mine site. The potential maximum mudflow depths would be less than two feet. 3.6.3 50-Year Mud Flood Event The flow velocity at the end of the model run is about zero feet per second. The simulated mud flood would travel west from Smuggler Mountain through Spruce Street, Silverlode Drive, Park Circle, and the developed area and communities. The potential mud flood hazard areas are the neighborhoods and communities close to Silverlode Drive, Williams Ranch Drive, Spruce Street, Teal Court, Free Silver Court, and Park Circle. The potential mudflow produced from the Smuggler Mine site would inundate the neighborhoods and communities next to Oak Lane, Ajax Avenue, and Park Circle. The potential maximum mudflow depths would occur at the front entrance of the building at the end of Spruce Street (0.8 ft), Oak Lane (1.1 ft), the front yard of a residential building at mid of Silverlode Drive (1.0 ft), the landscape pond at the northeast end of Race Street (2.7 ft), and the on-site pond at the Smuggler Mine site. 3.6.4 100-Year Mud Flood Event The simulated mud flood would travel west from Smuggler Mountain through the developed areas and flow into Roaring Fork and Hunter Creek. The mud flood would be conveyed by Spruce Street, Silverlode Drive, Park Circle, Vine Street, Gibson Avenue, South Avenue, Ajax Avenue, Oak Lane, Cottonwood Lane, Maple Lane, Teal Court, Free Silver Court, and East Francis Street. The potential mud flood hazard areas are the neighborhoods and communities close to Silverlode Drive, Williams Ranch Drive, Spruce Street, Teal Court, Free Silver Court, and Vine Street. The potential mudflow produced from the Smuggler Mine site would inundate the neighborhoods and communities next to Ajax Avenue, Oak Lane, Cottonwood Lane, Maple Lane, Gibson Avenue, East Francis Street, and North Spring Street. The potential maximum mudflow depths would occur at the north side of the building at the end of Spruce Street (2.2 ft), a building side yard next to Spruces Street (2.2 ft), the low elevation areas on Oak Lane (2.8 ft), the landscape pond at the northeast end of Race Street (8.5 ft), and the on-site pond at the Smuggler Mine site. 3.6.5 Yellow Zones Based on Aspen’s guidelines, areas with mudflow depth greater than 2 feet on the 100-year mudflow inundation map are defined as yellow mudflow zones on the mudflow hazard map. Figure 3.10 shows the delineated yellow zones from the FLO-2D modeling outputs. 3.7 DISCUSSION The purpose of the FLO-2D mudflow modeling was to determine the level of risk the existing buildings face during a mudflow event. The modeling results could be further used for evaluating the potential effects on a new development or a redevelopment during a mudflow event. The delineated mudflow areas agree in general with the observed mud slide event from May 2008. P120 I. April 2015 3-17 | Mudflow Analysis The FLO-2D modeling results depict areas which may be at high risk from mudflows and mud floods. Based on the model results, the watershed areas above the parking lot on Teal Court, Spruce Street, Silverlode Drive, and Oak Lane appear to have high risk for mudflow hazard as shown on Figures 3.6 through 3.9. Based on the current conditions, the mud flow depth would be less than two feet within the most of the delineated impacted area. The areas with mudflow depth greater than two feet on the 100-year mudflow inundation map are defined as yellow mudflow zones and shown in Figure 3.10. Due to the relative uncertainty associated with the data and modeling assumptions, the computed mudflow depths from this study should be considered as qualitative values for planning purposes only. P121 I. 3-18 | Mudflow Analysis April 2015 This page intentionally left blank P122 I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST SPRUCE ST SPRUCESTBROWNLN"Smuggler Mine On-Site Pond8110 830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 8420801079707870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 78607 9 3 0 86607930 7 9 0 0 788078507900 84307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 2-Year Event Smuggler/Hunter Surface Drainage Master Plan 3.6 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-06 Mudflow 2 year.mxd Plot Date: 1/9/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P123I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST SPRUCE ST SPRUCESTBROWNLN"Smuggler Mine On-Site Pond 8110830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 7900 8 0 9 0 842079707870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 8370832078907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 78607 9 3 0 86607930 7 9 0 0 788078507900 84307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 10-Year Event Smuggler/Hunter Surface Drainage Master Plan 3.7 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-07 Mudflow 10 year.mxd Plot Date: 1/9/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P124I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGSTVINEST "Smuggler Mine On-Site Pond"Landscape Pond 811083008290828082708310826082508240823082208210 82008190818081708160797081508140798078908130803081207990804081008090 801080808070802080007 9 2 0 8050791079607900 795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 84208010797080507870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 79107980786081207940 84507890 793079507840789078907 8 4 0 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 786086607930 7 9 0 0 788078507900 814084307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Maximum Mudflow Depth 50-Year Event Smuggler/Hunter Surface Drainage Master Plan 3.8 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-08 Mudflow 50 year.mxd Plot Date: 1/9/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P125I. Roar i ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGST "Smuggler Mine On-Site Pond"Landscape Pond 8110830082908280827083108260825082408230822082108200819081808170 816079708150814079807890 8130803081207990804081008090801080808070802080007 9 2 0 8050791079607900795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 7900 8 0 9 0 84207870 79607840 865079307 8 9 0 787083907930 7 9 3 0 7880 84407950791079307 8 5 0 7940 791079807860794084507890 793079507840789078907 8 4 0 837083207960 7870 7940 7930 7980795079207860 7 8 4 0 786086607930 7 9 0 0 788078507900 84307910 8 0 7 0 7880790079507900 7900 7910 7960793078607910 7890 0 300 Feet o Maximum Mudflow Depth 100-Year Event Smuggler/Hunter Surface Drainage Master Plan 3.9 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-09 Mudflow 100 year.mxd Plot Date: 1/9/2015 Legend Buildings Maximum Mudflow Depth (ft) < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 6.0 General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P126I. " 777 Spruce St. " Oak Lane"633 Spruce Street Roari ngFor kRi ver Hunter Creek GIBSONAVE SPRUCESTPARKCIREMAINSTREDMTNRD SILVERLODEDRNMILLSTLONEPINERD NSPRINGSTKINGST R I O G R A N D E P L SMUGGLERMTNRDNEALEAVERACESTSESAMESTNI CHOLASLNSPRUCECTWILLIAMSWAYWALNUTSTSGALENASTBAYST SHUNTERSTEBLEEKERST MATCHLESSDRSSPRINGSTNGALENASTQUEENSTRECYCLECIRNSPRINGST "Smuggler Mine On-Site Pond"Landscape Pond 811083008290828082708310826082508240823082208210 82008190818081708160797081508140798078908130803081207990804081008090 8010808080708020800079208050791079607900795079307940 832083308340835083607880 83708380839084008410786078707850 842084308440845084608470848084908500851085208530806085408550856085 708 5 8 0 8590860086108620863086407840 8650866086708680869087008710 80107900 8 0 9 0 84208010797080507870 79607840 865079307 8 9 0 7960787083907 9 3 0 7930 7 9 3 0 7880 84407950791079307 8 5 0 7940 79107980786081207940 84507890 793079507840789078907 8 4 0 7920 837083208180 78907940 7960 7870 7940 7930 7980795079207940 7860 7910 7 8 4 0 786086607930 7 9 0 0 788078507900 814084307910 8 0 7 0 78808070 790079507900 7900 7910 7960793078607910 7890 80600 300 Feet o Mudflow Hazard Yellow Zones Smuggler/Hunter Surface Drainage Master Plan 3.10 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig3-10 Mudflow Yellow Zones.mxd Plot Date: 1/9/2015 Legend Buildings Yellow Mudflow Zones General Note:Due to the methods, procedures, and assumptions used to develop the inundation areas, the limits of the mud/debris flooding shown are approximate and should be used only as a guideline for establishing hazard zones. Actual areas inundated will depend on actual runoff conditions and may differ from the areas shown on this map.P127I. P128I. SECTION FOUR SNOWMELT ANALYSIS April 2015 4-1 | Snowmelt Analysis 4 Section 4 FOUR Snowmelt Analysis 4.1 INTRODUCTION Aspen experiences sufficient snowfall throughout the fall, winter, and spring seasons to accumulate a significant snow pack both in the urban parts of town as well as in the headwaters of watersheds. Melting of this snow pack releases large volumes of water and is a stormwater runoff condition that must be evaluated so the impacts to the drainage systems, roadways, structures and facilities in the Study area are understood and improvements can be recommended if needed. The EPA SWMM 5 (SWMM 5) model was used to compute snowmelt runoff from each sub- basin by using the degree-day method approach (Reference 51), which is included in the SWMM 5 model interface. Input data for the snowmelt analysis includes time series data of air temperature, snowmelt coefficients, and snow water equivalent snow pack for each sub-basin. These input parameters were entered into the model via the Snow Pack Editor. 4.1.1 Theory In EPA SWMM 5 program, a lumped approach is used to generate a runoff hydrograph for each sub-basin. The rainfall intensity is the input control volume on the ground surface and the output is a combination of runoff and infiltration. The flow resistance and travel time are controlled by surface roughness and basin geometry characteristics. Manning’s equation is used to estimate flow velocity at each sub-basin outlet. For snowmelt modeling, SWMM 5 converts snowmelt rates to rainfall intensity via the degree-day method, and then computes exceeded runoff for each sub-basin. The degree-day method of estimating snowmelt within SWMM 5 uses the following equation: 𝑃𝑠=𝐾𝑠∙(𝑇−32℉) Where Ps = snowmelt rate (inch/day); Ks = snowmelt coefficient in (inch/day-°F); and T = air temperature in °F. A calibrated Ks was found to be 0.011 inch/day-°F or 0.00046 inch/hour-°F for Aspen (Reference 1). The resulting snowmelt depth is controlled solely by the temperature time series input generated by the temperature-frequency analysis for the 2-, 5-, 10-, 25-, 50-, and 100-year diurnal temperature swings within the Aspen area. 4.1.2 Extreme Temperature-Frequency Analysis Based on historical data from the Aspen area, snow depth was observed to generally accumulate from October to March, and usually begins melting from March to May. Figure 4.1 shows the average, daily snow water equivalent depth from the Aspen 1 SWM, Colorado (050372) snow gage station which is located south of Aspen, approximately one-half mile up Castle Creek Road. The station is at an elevation of approximately 8,160 feet. The climate summary for Aspen is presented in Table 4.1 (Reference 1). The snow water equivalent depth for this area based on the snow gage station was found to generally be 1-inch in May which would result in minimal flooding due to small potential snow water equivalent storage that can melt and runoff. Historically colder temperatures in March seldom seemed to cause flood events due to snowmelt due to the lower temperatures as the snowmelt rate is a function of the difference of the daily temperature and 32°F. Therefore, a temperature frequency analysis was conducted for the month P129 I. 4-2 | Snowmelt Analysis April 2015 of April based on the historic available snow pack data and higher reported temperatures for the month that would result more rapid snowmelt. The mean, maximum, and minimum temperatures in April were obtained from Western Regional Climate Center, Station 050372 at Aspen 1 SW, and Station 050370 in Aspen. For the frequency analysis, there was a total of 80 years of recorded data from a historical period of 99 years. Climate records from 1914-1980 were taken from Station 050370 in Aspen and compiled with climate records from 1981-2012 from Station 050372 at Aspen 1 SW. The average temperature observed at Station 050372 was generally 0.5 °F higher when compared to Station 050370 due to the differences in weather station’s elevations. To combine these two data time-series, the average temperature difference was used to adjust the temperatures observed in Station 050372 by subtracting 0.5°F from each data point and then combining with the temperature records in Station 050370 to form a composite series. An annual, non-parametric frequency analysis was performed for the extreme maximum temperature and average temperature data collected in April where temperatures for the 2-, 5-, 10-, 25-, 50-, and 100-year return periods were estimated. This was done by sorting the entire data for all historical temperatures for the month of April in descending order. Then each data point was ranked from highest March temperature to the lowest March temperature with the highest being 1. After ranking, each rank number was divided by the total number of data points plus 1 (called the Weibull distribution). This number represents the frequency potential of occurrence of each temperature. Temperature probabilities for the 2-, 5-, 10-, 25-, 50-, and 100- year return periods were extracted by interpolating the ranked data probabilities for the inverse of each return period. This non-parametric approach was completed three separate times for the daily minimum, maximum, and average historic temperature data series. The resulting estimated frequency-temperatures for the daily minimum, maximum, and average temperatures for the month of April are shown in Table 4.2. Digital files for the frequency analysis are included in Appendix D. Figure 4.1. Average Daily Snow Water Equivalence Depths from Aspen Weather Station 050372 P130 I. April 2015 4-3 | Snowmelt Analysis Table 4.1 Monthly Statistics for Daily Temperature and Precipitation in Aspen (Original Table 2.1 in URMP) Table 4.2 Daily Temperature Frequency Analysis for April in Aspen, Colorado 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year Mean Daily Temperature (°F)1 39.1 41.7 42.6 43.6 43.9 44.2 Max. Daily Temperature (°F)1 67.0 71.0 72.5 73.5 75.0 79.0 Min. Daily Temperature (°F)2 10.51 4.51 2.51 -2 -3 -10 Temperature Amplitude (°F) 28.2 33.2 35.0 37.8 39.0 44.5 Notes: 1. Computed results from the probability-frequency analysis. 2. Min. Daily Temperature = 2* (Max. Daily Temperature) – (Mean. Daily Temperature). °F = Degrees Fahrenheit Generally, temperatures are higher in the day than night and the snowmelt rate mainly depends on air temperatures. According to Part 630 Hydrology of the NRCS National Engineering Handbook (Reference 50), a sine curve is suggested to represent the temperature variation within a day. Using the sine curve, the temperature at any time could be determined by: 𝑇=𝑇𝑤+𝐴∙sin[15°(𝑡+𝐶)] where T = air temperature in °F at time t, Ta = mean air temperature for the day, A = amplitude, (Tmax-Tmin)/2, t = hour of the day, and C = time shift in hours when the maximum temperature will occur during the day (assumed to be 16 hours or 2:00 pm). The resulting daily temperature distributions used for the snowmelt analysis return periods are shown in Figure 4.2 and Table 4.3. P131 I. 4-4 | Snowmelt Analysis April 2015 Figure 4.2 Daily Temperature-Frequency Distributions Table 4.3 Daily Temperature-Frequency Distributions Time (Hour) 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0 14.3 9.0 7.2 3.1 2.2 -4.0 1 11.5 5.6 3.7 -0.7 -1.7 -8.5 2 10.5 4.5 2.5 -2.0 -3.0 -10.0 3 11.5 5.6 3.7 -0.7 -1.7 -8.5 4 14.3 9.0 7.2 3.1 2.2 -4.0 5 18.8 14.2 12.8 9.1 8.4 3.0 6 24.6 21.1 20.0 16.9 16.5 12.3 7 31.4 29.2 28.4 26.0 25.9 23.0 8 38.8 37.8 37.5 35.8 36.0 34.5 9 46.1 46.4 46.6 45.5 46.1 46.0 P132 I. April 2015 4-5 | Snowmelt Analysis Table 4.3 Daily Temperature-Frequency Distributions Time (Hour) 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 10 52.9 54.4 55.0 54.6 55.5 56.8 11 58.7 61.3 62.3 62.4 63.6 66.0 12 63.2 66.5 67.8 68.4 69.8 73.0 13 66.0 69.9 71.3 72.2 73.7 77.5 14 67.0 71.0 72.5 73.5 75.0 79.0 15 66.0 69.9 71.3 72.2 73.7 77.5 16 63.2 66.5 67.8 68.4 69.8 73.0 17 58.7 61.3 62.3 62.4 63.6 66.0 18 52.9 54.4 55.0 54.6 55.5 56.8 19 46.1 46.4 46.6 45.5 46.1 46.0 20 38.8 37.8 37.5 35.8 36.0 34.5 21 31.4 29.2 28.4 26.0 25.9 23.0 22 24.6 21.1 20.0 16.9 16.5 12.3 23 18.8 14.2 12.8 9.1 8.4 3.0 24 14.3 9.0 7.2 3.1 2.2 -4.0 4.1.3 Snowmelt Coefficient, Ks , and Elevation Lapse The snow gage station, 050372 at Aspen 1 SW, is located at an approximate elevation of 7,930 feet. The elevation range in the study area varies from 7,845 feet to 10,545 feet. A lapse rate of 2.5 °F/1000 feet was adopted from the Surface Drainage Master Plan for the City of Aspen (WRC Engineering Inc., 2001). This indicates that air temperature within the Study Area could vary by approximately 6.8 °F from the base of to the very upper reaches. Therefore, snowmelt rates were stratified into four elevation bands within the Study Area (Figure 4.3). For each sub- basin, the snowmelt rate was calculated using the following equation: 𝑃𝑠−𝐸𝐸=𝐾𝐸𝐸−𝑏𝑤𝑏𝑏�𝑇𝐴𝑠𝐴𝑤𝑏−32°� where Ps-El = snowmelt depth (inch/hour) in a certain elevation band, Ks = degree-day snowmelt coefficient (inch/hour-°F) for each elevation band, and TAspen = temperature in °F in Aspen resulting from temperature frequency analysis shown in Figure 4.2 and Table 4.3. Table 4.4 shows the temperature-frequency relationships for each elevation band. Table 4.5 presents the computed snowmelt coefficients for each return period and elevation band that were inputted in the SWMM 5 model to generate snowmelt runoff hydrographs for each sub-basin. P133 I. 4-6 | Snowmelt Analysis April 2015 Figure 4.3. Elevation Bands in the Study Area in Aspen, Colorado Table 4.4 Temperature-Frequency in April for Each Elevation Band within the Study Area in Aspen, Colorado Return Period (Year) Band 7500-8500 Band 8500-9500 Band 9500-10500 Band 10500-11500 Aspen Metro Area 2 67.0 64.5 62.0 59.5 5 71.0 68.5 66.0 63.5 10 72.5 70.0 67.5 65.0 25 73.5 71.0 68.5 66.0 50 75.0 72.5 70.0 67.5 100 79.0 76.5 74.0 71.5 P134 I. April 2015 4-7 | Snowmelt Analysis Table 4.5 Snowmelt Coefficient-Frequency in April for Each Elevation Band within the Study Area in Aspen, Colorado Return Period (Year) Snowmelt Coefficient (cubic feet/hour-°F) Band 7500-8500 Band 8500-9500 Band 9500-10500 Band 10500-11500 in./hr-°F cf./hr-°F in./hr-°F cf./hr-°F in./hr-°F cf./hr-°F in./hr-°F cf./hr-°F 2 0.00046 752 0.00043 465 0.00039 448 0.00036 7 5 0.00046 752 0.00043 468 0.00040 455 0.00037 7 10 0.00046 752 0.00043 470 0.00040 458 0.00037 7 25 0.00046 752 0.00043 470 0.00040 460 0.00038 7 50 0.00046 752 0.00043 471 0.00041 462 0.00038 8 100 0.00046 752 0.00043 474 0.00041 467 0.00039 8 Notes: cf. = cubic feet; °F = Degrees Fahrenheit 4.1.4 Model Inputs The determined frequency-daily temperature distribution and snowmelt coefficients were input into the SWMM 5 model to generate 2-, 5-, 10-, 25-, 50-, and 100-year snowmelt hydrographs. Daily temperature distributions were input as hourly time series and impacts due to sublimation and wind were ignored. Aspen’s URMP recommended values for Antecedent Temperature Index (ATI), Negative Melt Ratio, study area elevation, Latitude, and Longitude Correction are 0.5, 0.6, 8100 feet, 39.2, and 0.0, respectively. As the snow melting process proceeds, the area covered by snow gets reduced. In the SWMM 5 model, this behavior is described by an Areal Depletion Curve that plots the fraction of total area that remains snow-covered against the ratio of the actual snow water equivalent depth to the depth at which there is 100% snow cover. The SWMM 5 default curves for Natural Area and No Depletion were adopted for this study to be conservative by ensuring there is always ample snow pack available to melt when the temperature increases above freezing. The snow pack parameters were input in the Snow Pack Editor in SWMM 5. A constant snowmelt coefficient was assigned to each elevation band from Table 4.5. Snowmelt was set to begin at a base temperature of 32 °F. Dry snow pack was assumed as the initial conditions. The average snow water equivalent depth of 20 inches for the month of April, based on the Aspen 1 SWM, Colorado (050372) snow gage station, was input as the initial snow water equivalent in the model. Snow Removal Parameters are operation variables that describe how snow removal occurs within the plowable area of snow pack. According to Aspen’s Snow Plowing Plan, street snow is plowed when there is 3 inches or more of snowfall in one event. Therefore, a 3-inch depth was used to initiate snow removal within the SWMM 5 model. All removed, or plowed, snow was transferred to impervious areas which were estimated to be approximately 68% of the total area based on aerial imagery within the 7,500-8,500 study area elevation band. The ground soil was assumed to be frozen, and no infiltration losses were assumed during each the snowmelt simulation. P135 I. 4-8 | Snowmelt Analysis April 2015 All sub-basin outfalls within the SWMM 5 model were labeled with a prefix “O” to be transferred back into the existing InfoSWMM models created for each basin. Each basin’s InfoSWMM model created for the rainfall analysis was copied into a separate folder and modified by labeling each sub-basin inflow hydrograph node with a prefix “O” to link all snowmelt hydrographs for each return period with their corresponding sub-basin. All model elements within each InfoSWMM model remained the same as the rainfall analysis to route snowmelt runoff generated from each sub-basin. Digital files for the InfoSWMM snowmelt analysis are included in Appendix D. 4.1.5 Results and Discussion Resulting snowmelt Design Point summary tables showing peak conduit flow rates and cumulative snowmelt volumes at each node are shown in Table 4.6. Peak flow snowmelt rates were substantially less than rainfall peak flows for each snowmelt extreme temperature return period. Cumulative snowmelt volume was also reported for each modeling node in each basin Design Point summary table for snowmelt. Because peak flow snowmelt rates were so low in each basin relative to rainfall, a basin-by-basin description of deficient drainage systems is not necessary. Although peak snowmelt runoff is not a threat relative to rainfall runoff values, snowmelt cumulative volume can pose as flooding threat in areas with engineered drainage systems. Areas can become flooded due to snow maintenance practices. Excess snow can be moved to areas such as storm inlets or depressed areas and affect the originally designed drainage patterns. Snow piles can also act as dams in areas and restrict large amounts of snowmelt from draining from an area. All existing storm systems were shown to convey the 100-year snowmelt runoff peak flow for all basins with the exception of all dry wells, which could not contain the 2-year temperature event cumulative volume nor attenuate any snowmelt frequency peak flow. All modeled retention, detention, and underground infiltration basins were also inherently able to retain the 100-year snowmelt volume. However, the private underground detention tank P03-N16 was unable to contain the 2-year snowmelt peak flow. Snowmelt summary tables are highlighted to designate areas that had no storm system and had the potential of flooding and also areas that had known reported areas of snowmelt flooding on Table 4.6. P136 I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OH01 C56-H03 -Spruce St. & Spruce Ct.Overland runoff 55.5 Local -0.4 0.5 0.5 0.6 0.6 0.7 ------14,438 18,715 20,186 21,523 22,592 25,132 OH02 C19-H02 -Salvation Ditch Overflow Overland runoff 8.7 --0.1 0.1 0.1 0.1 0.1 0.1 ------2,674 3,342 3,609 3,877 4,010 4,412 OFALL-11 --Williams Woods Outfall Outfall 77.7 --------------21,122 27,271 29,410 31,415 32,885 36,495 OH05 C58-H05 -Overland runoff Swale 11.5 --0.2 0.2 0.2 0.2 0.2 0.2 ------3,609 4,545 4,946 5,214 5,347 5,882 OFALL-12 --Hunter Creek Development Outfall Outfall 11.5 --------------3,609 4,545 4,946 5,214 5,347 5,882 OH04 C59-H04 O59-H04 Red Mountain Road Bridge Inlet 12" CMP 3.0 Local 6 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 936 1,203 1,337 1,337 1,471 1,604 OFALL-13 --Red Mountain Road Bridge Outfall Outfall 3.0 --------------936 1,203 1,337 1,337 1,471 1,604 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of snowmelt flooding. * Approximate values. **Assumed pipe size. Conduit Peak Flow (cfs) Red Mountain Road Outfall Overflow Peak Flow (cfs) Hunter Creek Basin Snowmelt Williams Woods Outfall Hunter Creek Development Outfall Cumulative Snowmelt Volume (cf) SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Page 1 of 6 P137I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OG04 C06-G04 O06-G04 Silverlode Dr. (West)12" HDPE 12.62 Local 11 0.1 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,877 4,946 5,214 5,615 5,882 6,417 DW01-G04 ORI01-G04 WEIR01-G04 Silverlode Dr. (West)12" CMP/ Dry Well 12.62 Local 6 0.1 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,877 4,946 5,214 5,615 5,882 6,417 DW02-G04 OLET-DW02-G04 WEIR02-G04 Silverlode Dr. (West)Dry Well 12.62 Local 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.2 0.2 0.2 0.2 3,743 4,813 5,214 5,481 5,748 6,417 OG02 C05-G02 O05-G02 Silverlode Dr. (Center)24" RCP 2.57 Local 36 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 1,069 1,069 1,203 1,203 1,337 D05-G02 C04-G02 O04-G02 Silverlode Dr. (Center)24" CMP 2.57 -58 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 1,069 1,069 1,203 1,203 1,337 D06-G02 C03-G02 O03-G02 Silverlode Dr. (Center)24" CMP 2.57 -30 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 1,069 1,069 1,203 1,203 1,337 OG01 C01-G01 O01-G01 Williams Ranch Dr. (East)24" RCP 12.32 Local 54 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,877 4,813 5,214 5,481 5,748 6,417 D02-G02 C02-G02 O02-G02 Williams Ranch Dr. (East)24" CMP 12.32 Local 49 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,877 4,813 5,214 5,481 5,748 6,417 D03-G02 C07-G02 O07-G02 Upper Gibson Ave Confluence 36" CMP 14.89 -83 0.2 0.2 0.2 0.2 0.3 0.3 0.0 0.0 0.0 0.0 0.0 0.0 4,679 5,882 6,283 6,684 6,951 7,620 DW08-G03 OLET-DW08-G03 WEIR03-G03 1st Dry Well in Series Dry Well 1 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 4,813 6,149 6,550 6,951 7,219 8,021 DW05-G03 OLET-DW05-G03 WEIR04-G03 2nd Dry Well in Series Dry Well 2 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 4,545 5,748 6,283 6,684 6,951 7,754 DW06-G03 OLET-DW06-G03 WEIR06-G03 3rd Dry Well in Series Dry Well 3 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 4,278 5,481 6,016 6,417 6,684 7,352 DW03-G03 OLET-DW03-G03 WEIR07-G03 4th Dry Well in Series Dry Well 4 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 4,010 5,214 5,615 6,016 6,417 7,085 DW07-G03 OLET-DW07-G03 WEIR08-G03 5th Dry Well in Series Dry Well 5 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 3,609 4,946 5,347 5,748 6,016 6,818 DW04-G03 OLET-DW04-G03 WEIR09-G03 6th Dry Well in Series Dry Well 6 15.51 -0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.3 0.3 0.3 3,476 4,679 5,214 5,615 5,882 6,684 P01-G03 OLET-P01-G03 WEIR10-P01-G03 Underground Seepage Area Seepage Area 15.51 -22 0.1 0.1 0.1 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,208 4,412 4,946 5,347 5,615 6,283 J03-G06 C10-G05 -Confluence of Upper Gibson Confluence 28.13 --0.1 0.2 0.2 0.2 0.2 0.2 ------3,476 4,545 4,946 5,214 5,481 6,149 OG05 C12-G05 O12-G05 Lone Pine Rd Crossing 18" CMP**39.63 Local 9 0.9 0.9 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 123,788 125,660 126,328 126,997 127,531 128,601 OG13 C13-G13 O13-G13 Lone Pine Rd. Grate Inlet 18" CMP 42.31 Local 12 0.9 1.0 1.0 1.0 1.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 124,590 126,729 127,531 128,200 128,734 129,938 OG08 C27-G08 O27-G08 River Bluff Townhome Intake 8" PVC**47.72 -1.4 1.0 1.0 1.1 1.1 1.1 1.2 0.0 0.0 0.0 0.0 0.0 0.0 126,061 128,734 129,670 130,472 131,007 132,611 D08-G08 C25-G08 O25-G08 River Bluff Townhome Outlet 6" CPP 47.72 -0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.7 126,061 128,601 129,537 130,339 131,007 132,477 D09-G10 C24-G10 O24-G10 Red Mtn Rd. off road 18" CMP 47.72 -7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 0 0 0 0 D10-G10 C31-G10 O31-G10 Red Mtn Rd. crossing 12" CMP**47.72 -8 1.0 1.0 1.1 1.1 1.1 1.2 0.0 0.0 0.0 0.0 0.0 0.0 126,061 128,601 129,537 130,339 131,007 132,477 OFALL-2 --Red Mtn. Rd. Outfall Outfall 47.72 --------------126,061 128,601 129,537 130,339 131,007 132,477 OG06 C16-G06 O16-G06 Lone Pine Rd. & Rd Mtn. Rd.24" CMP 2.40 Arterial 32 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 936 1,069 1,069 1,069 1,203 OFALL-1 --Lone Pine Rd. Outfall Outfall 2.40 --------------802 936 1,069 1,069 1,069 1,203 Gibson Ave. Storm System OG07 C19-G09 O19-G09 Gibson Ave. Storm System 24" CMP 1.46 Arterial 27 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401 535 668 668 668 802 D07-G09 C20-G09 O20-G09 Gibson Ave. Stem 18" CMP 1.46 -15 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401 535 668 668 668 802 OG09 C22-G09 O22-G09 Gibson Ave. Curb Inlet 12" PVC 2.91 Arterial 10 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401 535 668 668 668 802 D08-G10 C21-G10 O21-G10 Gibson Ave. Storm Stem 18" CMP 2.91 -7 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 936 1,203 1,203 1,337 1,337 1,471 OG10 C18-G11 O18-C11 Red Mtn Rd Crossing 18" CMP 51.29 Arterial 15 0.0 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 1,069 1,471 1,471 1,604 1,738 1,872 OFALL-3 --Gibson Ave. Outfall Outfall 51.29 --------------1,069 1,471 1,471 1,604 1,738 1,872 OG11 C17-G11 O17-G11 Bridge Curb Inlet at N. Mill St.12" CMP 0.67 Arterial 4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 267 267 267 267 267 401 OFALL-4 --N. Mill St. Bridge Outfall (N.)Outfall 0.67 --------------267 267 267 267 267 401 OG12 C23-G12 O23-G12 Bridge Grate Inlet at N. Mill St.12" CMP 0.19 Arterial 8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 134 134 134 134 134 OFALL-5 --N. Mill St. Bridge Outfall (S.)Outfall 0.19 --------------0 134 134 134 134 134 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of flooding. * Approximate values. **Assumed pipe size. Gibson Avenue Basin Snowmelt Cumulative Snowmelt Volume (cf) Upper Gibson Ave Basin Lone Pine Rd. Outfall N. Mill St. Bridge SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Conduit Peak Flow (cfs)Overflow Peak Flow (cfs) Page 2 of 6 P138I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 19 0.2 0.2 0.2 0.2 0.2 0.3 0.0 0.0 0.0 0.0 0.0 0.0 3,743 4,946 5,347 5,748 6,016 6,684 ON09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 4.2 0.2 0.2 0.3 0.3 0.3 0.3 0.0 0.0 0.0 0.0 0.0 0.0 4,278 5,615 6,149 6,550 6,951 7,754 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local -0.2 0.2 0.3 0.3 0.3 0.3 ------4,278 5,615 6,149 6,550 6,818 7,620 ON05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 7 0.3 0.3 0.4 0.4 0.4 0.4 0.0 0.0 0.0 0.0 0.0 0.0 6,016 8,155 8,823 9,358 9,892 10,962 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 --0.0 0.1 0.1 0.2 0.2 0.4 ------12,432 18,849 20,319 21,656 22,592 25,132 ON08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 25 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401 535 668 668 668 802 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local -0.0 0.1 0.1 0.2 0.2 0.4 ------401 3,208 4,679 6,016 7,085 9,625 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local -0.3 0.4 0.4 0.4 0.4 0.6 ------5,748 10,427 12,566 14,571 16,042 19,651 ON04 C16-N04 O16-N04 Silverlode Dr.12" CMP 9.1 Local 4 0.1 0.1 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 2,941 3,877 4,144 4,412 4,545 5,080 ON11 C25-N04 -Silverlode Dr.Road runoff 0.7 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------267 267 267 267 267 401 DW02-N04 OLET-DW02-N04 WEIR01-N04 Silverlode Dr. & Smuggler Mtn. Rd.Dry Well 9.1 Local 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.2 0.2 0.2 0.2 2,941 3,877 4,144 4,412 4,545 5,080 ON10 C12-N10 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 12" CMP 90.0 Local 4 0.4 0.5 0.6 0.6 0.6 0.7 0.0 0.0 0.0 0.0 0.0 0.0 9,224 14,839 17,379 19,517 21,255 25,399 DW01-N10 OLET-DW01-N10 WEIR02-N10 Park Cir. & Smuggler Mtn Rd.Dry Well 90.0 Local 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.5 0.6 0.6 0.6 0.7 9,224 14,839 17,379 19,517 21,255 25,399 ON13 C29-N13 O29-N13 End of Tributary at Brown Ln.12" PVC 95.7 Local 2.1 0.5 0.6 0.6 0.7 0.7 0.8 0.0 0.0 0.0 0.0 0.0 0.0 10,828 16,977 19,651 22,057 23,929 28,340 ON02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -165 0.5 0.6 0.7 0.7 0.8 0.8 0.0 0.0 0.0 0.0 0.0 0.0 14,037 20,854 22,458 23,795 24,998 27,672 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 112 0.5 0.6 0.7 0.7 0.8 0.8 0.0 0.0 0.0 0.0 0.0 0.0 14,037 20,854 22,458 23,795 24,998 27,672 ON07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 10 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 401 535 668 668 668 802 J20-12 C34-N12 -Free Silver Ct.Ditch 60.9 --0.5 0.6 0.7 0.7 0.8 0.9 ------14,571 21,389 22,993 24,464 25,667 28,474 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local -0.5 0.6 0.7 0.7 0.8 0.9 ------14,438 21,389 22,993 24,464 25,667 28,474 D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 11 0.5 0.6 0.7 0.7 0.8 0.9 0.0 0.0 0.0 0.0 0.0 0.0 14,438 21,389 22,993 24,464 25,667 28,474 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.12" PVC 60.9 Local 10 0.5 0.6 0.7 0.7 0.8 0.9 0.0 0.0 0.0 0.0 0.0 0.0 14,438 21,389 22,993 24,464 25,667 28,474 ON12 C28-N12 O28-N12 Brown Ln & Park Cir.12" PVC 156.6 Local 8 0.6 0.7 0.8 0.8 0.8 0.9 0.0 0.0 0.0 0.0 0.0 0.0 12,967 19,651 22,592 24,998 27,004 31,816 D2-N12 C30-N12 O30-N12 Brown Ln Inlet to Infiltration Tank 24" PVC 163.3 Local 46 1.1 1.4 1.4 1.5 1.5 1.7 0.0 0.0 0.0 0.0 0.0 0.0 27,405 41,040 45,585 49,462 52,670 60,290 J17-N17 C31-N17 -Brown Ln & Park Cir.Road runoff 163.3 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------0 0 0 0 0 0 P03-N16 OLET-P03-N16 WEIR03-N16 Centennial Apts. Underground Infiltration Tank 10'x80' Tank 163.9 -0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.5 0.8 0.8 0.9 1.0 1.2 27,672 41,307 45,852 49,863 53,071 60,557 J18-N17 C36-N17 -Park Cir.Road runoff 163.9 Local -0.5 0.8 0.8 0.9 1.0 1.2 ------3,476 9,090 11,363 13,234 14,972 21,122 ON17 C61-N17 O61-N17 Gibson Ave Inlet 12" CMP 167.5 Local 0.8 0.5 0.8 0.8 0.8 0.8 0.8 0.0 0.0 0.1 0.2 0.3 0.5 4,545 10,561 12,967 14,839 16,710 22,993 OFALL-1 --Oklahoma Flats Outfall Outfall 172.8 --------------6,283 12,833 15,106 17,245 19,116 25,800 ON15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 29 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 1,738 2,139 2,406 2,540 2,540 2,807 ON18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 3.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 1,069 1,069 1,203 1,203 1,337 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 13 0.1 0.1 0.1 0.1 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0 2,540 3,208 3,476 3,609 3,743 4,144 ON19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 59 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,342 4,278 4,545 4,813 5,080 5,481 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 23 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,342 4,278 4,545 4,813 5,080 5,481 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 15 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,342 4,278 4,545 4,813 5,080 5,481 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 12 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,342 4,278 4,545 4,813 5,080 5,481 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 67 0.2 0.2 0.2 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 3,342 4,278 4,545 4,813 5,080 5,481 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 35 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2,005 2,540 2,674 2,807 2,941 3,208 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 41 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2,005 2,540 2,674 2,807 2,941 3,208 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 55 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2,005 2,540 2,674 2,807 2,941 3,208 ON21 C49-N23 O49-N23 Neale Ave & Gibson Ave Confluence 36" CMP 21.8 Local 135 0.3 0.4 0.4 0.4 0.4 0.4 0.0 0.0 0.0 0.0 0.0 0.0 6,818 8,689 9,358 9,892 10,293 11,229 ON23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 38 0.3 0.4 0.4 0.4 0.4 0.5 0.0 0.0 0.0 0.0 0.0 0.0 7,754 9,892 10,561 11,229 11,630 12,833 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 27 0.3 0.4 0.4 0.4 0.4 0.5 0.0 0.0 0.0 0.0 0.0 0.0 7,754 9,892 10,561 11,229 11,630 12,833 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 3.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 0 0 0 0 OFALL-2 --Neale Ave. Outfall Outfall 24.8 --------------7,754 9,892 10,561 11,229 11,630 12,833 ON14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 9 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 1,471 2,005 2,139 2,273 2,406 2,540 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -19 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 1,738 2,273 2,406 2,540 2,674 2,941 OFALL-3 --Smuggler Mine Outfall Outfall 5.6 --------------1,738 2,273 2,406 2,540 2,674 2,941 ON22 C55-N24 -King St. (Flooding)Low Area; Flooding 1.7 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------535 668 668 802 802 936 OFALL-4 --Bibbig Exemption Outfall Outfall 5.1 --------------1,604 2,005 2,139 2,273 2,406 2,540 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of flooding. * Approximate values. **Assumed pipe size. Cumulative Snowmelt Volume (cf) Park Circle Tributary to Oklahoma Flats Outfall Neale Avenue & OK Flats Basin Snowmelt Oklahoma Flats Outfall Neale Avenue Storm System Smuggler Mine Outfall Bibbig Exemption Riverside Ditch Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Conduit Peak Flow (cfs)Overflow Peak Flow (cfs) Page 3 of 6 P139I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OFALL-05 --Callahan Outfall Outfall 6.0 --------------1,872 2,273 2,540 2,674 2,807 3,075 P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 --0.0 0.0 0.0 0.0 0.0 0.0 ------802 1,069 1,069 1,203 1,203 1,337 OFALL-09 --Gordon Outfall Outfall 1.3 --------------401 535 535 535 668 668 OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 -------------535 802 802 802 936 936 OR14 C60-R13 -Salvation Ditch & Hwy 82 Road runoff 2.58 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------802 1,069 1,069 1,203 1,203 1,337 J23-R13 C61-R13 -Fred Ln. & Riverside Dr.Road runoff 2.58 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------802 1,069 1,069 1,203 1,203 1,337 P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 11.7 --0.1 0.2 0.2 0.2 0.2 0.2 ------9,625 10,694 10,962 11,229 11,497 12,031 OFALL-07 WEIR06-P01-R15 -Gordon/Callhan 2 Outfall Outfall 11.7 --0.0 0.0 0.0 0.0 0.0 0.0 ------3,609 4,545 4,946 5,214 5,481 6,016 OR11 C16-R11 O16-R11 Eastwood Dr.12" CMP 7.7 Local 2.0 0.1 0.1 0.1 0.1 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0 2,406 3,075 3,342 3,476 3,609 4,010 OR09 C37-R19 -Hwy 82 Road runoff 15.7 Local -0.2 0.2 0.2 0.2 0.3 0.3 ------4,813 6,149 6,550 6,951 7,352 8,021 OR04 C23-R04 O23-R04 Salvation Ditch overflow Overland runoff 40.2 --0.4 0.5 0.5 0.5 0.6 0.6 ------12,165 15,373 16,576 17,646 18,448 20,319 J21-R19 C55-R19 -Alpine Ct. & E. Cooper Ave.Confluence/Runoff 55.9 Local -0.6 0.7 0.7 0.8 0.8 0.9 ------16,977 21,523 23,127 24,597 25,667 28,340 D05-R19 C50-R19 O50-R19 Midland Ave. & Cooper Ave.18" CMP 55.9 Local 13 0.6 0.7 0.7 0.8 0.8 0.9 0.0 0.0 0.0 0.0 0.0 0.0 16,977 21,523 23,127 24,597 25,667 28,340 OR12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------802 1,069 1,069 1,203 1,203 1,337 OR17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------668 802 936 936 936 1,069 J20-R19 C53-R19 -E. Cooper Ave. & Lacet Ln.Confluence/Runoff 4.7 Local -0.1 0.1 0.1 0.1 0.1 0.1 ------1,471 1,872 2,005 2,139 2,139 2,406 OR19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.18" CMP 68.4 Local 12 0.7 0.9 0.9 1.0 1.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 20,854 26,469 28,474 30,212 31,549 34,757 OFALL-10 --E. Cooper Ave. Outfall Outfall 68.4 --------------20,854 26,469 28,474 30,212 31,549 34,757 OR02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.2 0.2 0.2 0.2 0.2 0.3 ------4,946 6,417 6,818 7,352 7,620 8,556 OR03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --0.1 0.1 0.1 0.1 0.1 0.1 ------1,872 2,273 2,406 2,540 2,674 2,941 J17-R08 C43-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -0.2 0.3 0.3 0.3 0.3 0.4 ------6,684 8,556 9,224 9,892 10,293 11,363 OR08 C39-R08 -Snyder Park Overland runoff 10.0 --0.1 0.2 0.2 0.2 0.2 0.2 ------3,208 4,010 4,278 4,545 4,679 5,214 P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --0.1 0.2 0.2 0.2 0.2 0.2 ------25,132 25,934 26,201 26,469 26,602 27,137 P04-R08N WEIR02-P04-R08N -North Snyder Park Pond Aesthetic Pond 34.0 --0.3 0.4 0.4 0.5 0.5 0.5 ------30,880 33,688 34,623 35,425 36,094 37,698 J16-R10 C40-R10 -Midland Ave. & E. Hopkins Road runoff 34.0 Local -0.3 0.4 0.4 0.5 0.5 0.5 ------9,892 12,566 13,502 14,304 14,972 16,576 OR10 C41-R10 -Park Ave. & E. Hopkiins Ave.Road runoff 40.5 Local -0.4 0.5 0.5 0.6 0.6 0.6 ------11,898 15,106 16,309 17,245 18,047 19,918 OFALL-06 --E. Hopkins Ave. Outfall Outfall 40.5 --------------11,898 15,106 16,309 17,245 18,047 19,918 OR01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.3 0.4 0.4 0.5 0.5 0.6 ------9,625 12,165 13,101 13,903 14,571 16,175 J18-R05 C44-R05 -Mascotte Ln. & Ardmore Dr.Road runoff 31.6 Local -0.3 0.4 0.4 0.5 0.5 0.6 ------9,625 12,165 13,101 13,903 14,571 16,175 OR06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.1 0.1 0.1 0.1 0.1 0.1 ------1,471 2,005 2,139 2,273 2,273 2,540 J25-R05 C64-R05 -Miland Park Pl Road runoff 5.0 Local -0.1 0.1 0.1 0.1 0.1 0.1 ------1,471 1,872 2,005 2,139 2,273 2,540 OR07 C35-R07 O35-R07 Park Ave. & North side of Midland Ave.12" CMP 7.3 Local 11 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2,273 2,807 3,075 3,208 3,342 3,743 DW01-R07 INFIL-DW01-R07 WEIR03-DW01-R07 Park Ave. & Midland Ave.Dry Well 12.3 Local 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.5 0.5 0.6 0.6 0.6 3,743 4,813 5,080 5,347 5,615 6,283 J19-R05 C46-R05 -Park Ave.Road runoff 12.3 Local -0.3 0.5 0.5 0.5 0.5 0.6 ------3,476 5,748 6,149 6,417 6,283 7,085 OR05 C45-R05 -Park Ave. & Regent St.Road runoff 51.6 Local -0.7 1.0 1.0 1.1 1.1 1.2 ------17,111 22,993 24,731 26,068 26,870 29,811 OFALL-04 --Riverside Addition Outfall Outfall 51.6 --------------17,111 22,993 24,731 26,068 26,870 29,811 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of flooding. * Approximate values. **Assumed pipe size. Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID E. Hopkins Avenue Outfall (R) Riverside Addition Outfall (R) Riverside McSkimming Basin Snowmelt Callahan Outfall (R) Callahan Sub OS Retention (R) Gordon Outfall (R) Gordon/Callahan 1 Outfall (R) Conduit Peak Flow (cfs)Overflow Peak Flow (cfs)Cummulative Snomelt Volume (cf) Gordon/Callahan 2 Outfall (R) E. Cooper Avenue Outfall (R) SWMM Element ID Location Existing Structure Page 4 of 6 P140I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OE03 C04-E04 -Mtn. Laurel Drive Road runoff 11.6 Local -0.1 0.2 0.2 0.2 0.2 0.2 ------3,208 4,144 4,412 4,679 4,946 5,481 OE04 C05-E01 Mtn. Laurel Drive Road runoff 40.5 Local -0.4 0.5 0.5 0.5 0.6 0.6 ------10,962 14,170 15,373 16,309 17,111 18,849 OE01 C06-E02 -Mtn. Laurel Drive switchback Road runoff 125.6 Local -0.9 1.2 1.3 1.3 1.4 1.6 ------32,618 42,510 45,852 48,927 51,333 57,082 J06-E02 C13-E02 -Mtn Laurel Dr. & W. Lupine Dr.Road runoff 125.6 Local -0.9 1.2 1.3 1.3 1.4 1.6 ------32,618 42,510 45,852 48,927 51,333 56,948 J05-E02 C12-E02 -Roaring Fork Dr.Road runoff 125.6 Local -0.9 1.2 1.3 1.3 1.4 1.6 ------32,618 42,377 45,852 48,793 51,333 56,948 OE02 C01-E02 O01-E02 Hwy 82 crossing 18" CMP 150.5 Local 9 1.2 1.5 1.6 1.7 1.8 2.0 0.0 0.0 0.0 0.0 0.0 0.0 40,372 52,135 56,280 59,889 62,830 69,648 D02-E06 C09-E06 O09-E06 Downstream culvert of Hwy 82 18" CMP 150.5 -21 1.2 1.5 1.6 1.7 1.8 2.0 0.0 0.0 0.0 0.0 0.0 0.0 40,372 52,135 56,280 59,889 62,830 69,648 OFALL-01 --Knollwood Outfall Outfall 150.5 --------------40,372 52,135 56,280 59,889 62,830 69,648 OE05 C02-E05 O02-E05 Hwy 82 crossing 18" CMP 2.6 Arterial 5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 802 1,069 1,069 1,203 1,203 1,337 OE06 C07-E06 -Salvation Ditch overflow Overland runoff 6.2 --0.1 0.1 0.1 0.1 0.1 0.1 ------2,005 2,406 2,674 2,807 2,941 3,208 OFALL-02 --Stillwater Ranch Outfall Outfall 6.2 --------------2,005 2,406 2,674 2,807 2,941 3,208 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of flooding. * Approximate values. **Assumed pipe size. Cumulative Snowmelt Volume (cf) Eastwood Basin Snowmelt Knollwood Outfall Stillwater Ranch Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Conduit Peak Flow (cfs)Overflow Peak Flow (cfs) Page 5 of 6 P141I. Table 4.6 Snowmelt Summary Table 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year 2-year 5-year 10-year 25-year 50-year 100-year OS01 C01-S02 -Upper Mtn. Laurel Dr. low spot Road runoff 328.8 Local -0.8 1.2 1.3 1.4 1.6 1.9 ------53,071 77,401 84,887 91,571 101,196 114,431 OS02 C03-S08 -Mtn. Laurel Dr. curve/low spot Road runoff 330.3 Local -0.8 1.2 1.3 1.4 1.6 1.9 ------53,205 77,668 85,155 91,839 101,597 114,832 OS03 C05-S06 -Upper Mtn. Laurel Dr. low spot Road runoff 12.4 Local -0.1 0.2 0.2 0.2 0.2 0.2 ------3,476 4,412 4,813 5,080 5,347 5,882 OS06 C20-S08 -Mtn. Laurel Dr. low spot Road runoff 14.5 Local -0.2 0.2 0.2 0.2 0.2 0.3 ------3,609 4,813 5,214 5,615 5,882 6,550 J08-S08 C19-S08 -E. Lupine Dr.Confluence 344.8 Local -0.9 1.3 1.5 1.6 1.8 2.0 ------56,681 82,214 90,234 97,186 107,212 121,248 OS05 C07-S08 -Mtn. Laurel Dr. low spot Road runoff 4.3 Local -0.1 0.1 0.1 0.1 0.1 0.1 ------1,337 1,738 1,872 2,005 2,005 2,273 OS08 C06-S08 O06-S08 W. Lupine Dr. and Lupine Dr.Confluence 354.6 Local -1.0 1.4 1.6 1.7 1.9 2.2 0.0 0.0 0.0 0.0 0.0 0.0 59,488 85,823 94,111 101,330 111,623 126,061 OS09 C22-S09 O22-S09 Hwy 82 & Stillwater Dr.Confluence 357.0 Local -1.0 1.4 1.6 1.7 1.9 2.2 0.0 0.0 0.0 0.0 0.0 0.0 60,290 86,759 95,047 102,399 112,693 127,130 OFALL-2 C21-S09 -Northern Outfall Outfall 0.8 --------------60,424 87,026 95,314 102,667 112,960 127,531 OS04 C10-S07 -Mtn. Laurel Dr. S. low spot Road runoff 5.3 Local -0.1 0.1 0.1 0.1 0.1 0.1 ------1,604 2,139 2,273 2,406 2,406 2,674 P01-S07 WEIR01-S07 -E. Lupine Dr. low spot Private Detention 8.9 Local -0.0 0.0 0.0 0.0 0.0 0.0 ------2,406 3,075 3,342 3,476 3,743 4,144 OS10 C14-S10 -Hwy 82 Confluence 11.9 Local -0.0 0.0 0.0 0.0 0.0 0.1 ------936 1,203 1,203 1,337 1,337 1,604 OFALL-1 --Southern Outfall Outfall 13.8 --------------1,471 1,872 2,005 2,139 2,273 2,540 System sufficient if the peak snowmelt flow rate is less than the capacity of the system plus 15%. Capacity of the existing storm system plus 15% is less than the peak snowmelt flow rate. Potential areas of flooding that have no storm system. Known areas of flooding. * Approximate values. **Assumed pipe size. Cumulative Snowmelt (cf) Stillwater Bridge Basin Snowmelt Stillwater Dr. Outfall South Outfall SWMM Element ID Location Existing Structure Description Contributing Area (ac) Road Classification Capacity (cfs) Conduit ID Overflow ID Conduit Peak Flow (cfs)Overflow Peak Flow (cfs) Page 6 of 6 P142I. SECTION FIVE ALTERNATIVE DEVELOPMENT April 2015 5-1 | Alternative Development 5 Section 5 FIVE Alt ernative D evelopment 5.1 INTRODUCTION To manage stormwater runoff in the study area, alternatives for flood control were developed conceptually so that feasibility and cost of flood control projects could be estimated and compared. Generally, two basic strategies to mitigate flood hazards and improve water quality aspects were investigated for each basin: 1) sub-regional detention and, 2) conveyance improvements that include storm sewer improvements. In addition to these two design approaches, two additional scenarios were considered when developing each alternative for each major basin: 1) the “With Easements” scenario that minimizes storm sewer system costs by using the shortest feasible route and obtaining easements to cross private lands and, 2) the “Minimal or Without Easements” scenario, which uses longer storm sewer routes to minimize or eliminate private easements for each alternative to reduce cost due to the expensive cost of land in the study area. The objective of this alternatives evaluation was to identify cost effective measures to control stormwater runoff from the study area watersheds such that: 1) runoff can be conveyed safely within existing and proposed infrastructure, 2) the potential for damages to conveyances and buildings within each watershed from the design flood is reduced, and 3) flood control measures can be implemented effectively as development occurs and funding becomes available. After a feasible alternative was identified, it was conceptually designed according to established project criteria and modeled using InfoSWMM and other hydraulic software to confirm performance. After hydraulic modeling confirmed performance, conceptual-level cost estimates were prepared to assess and compare the cost effectiveness of each feasible alternative. This evaluation includes a listing of structural and conveyance improvements with the estimated total cost for each, and considering the benefits for each alternative. The costs account for property acquisition required for locating detention facilities and pipe alignments as well as estimating costs to design and construct the project. Other continuing costs, such as operation and maintenance, are not considered. Benefits identified include: • Areas made to convey the 100-year event without flooding • Reduction in the frequency of roadway overtopping or flooding • Storm systems designed to handle either the 5- or 10-year events • Reduction of long-term maintenance costs Implementation costs and benefits associated with each alternative were reviewed and one alternative for each basin was selected as the suggested plan for consideration by Aspen. 5.2 GOALS, CRITERIA, AND CONSTRAINTS Wherever possible, the criteria and methods used to develop detention and conveyance requirements follow the Aspen URMP and Engineering Standards (References 1 and 9). The minor (initial) design storms are either the 5- or 10-year event, and the major design storm is the 100-year event. Some of the urbanized parts of Aspen are served by existing storm sewer P143 I. 5-2 | Alternative Development April 2015 systems and major outfalls that have less capacity than needed to convey the minor event. Many areas lack any storm sewer system at all. Providing 100-year storm sewer outfalls in these areas would be extremely costly and not standard practice, so major storm sewer outfall improvements in highly urbanized areas are sized for the minor (5- or 10-year) events. Each alternative was developed to reduce flood impacts to public and private property, especially property that is highly developed and major roadway crossings. Alternatives were developed to also consider cost effectiveness and implementation. 5.2.1 Flood Impacts Several reaches within the study area were shown to have flooding during the 100-year event (See Figure 2.7). These modeled floodplain extents show a high flood risk to private structures during the 100-year event as well as impede travel along major roadways throughout Aspen. The relative flood risks for each basin were presented previously in Section 3. 5.2.2 Cost Effectiveness Construction costs were estimated for each alternative and compared to other alternatives, along with an evaluation of how well each alternative addresses previously mentioned drainage problem areas in Section 3. The criteria and process for estimating right-of-way and the financial costs, such as the use of assessor’s data for property costs in Pitkin County, was established using parcel GIS data costs obtained from Aspen and estimating the limits of disturbance based on the proposed structures size and depth. Cost effectiveness depends not only on the bottom line construction cost, but also the benefits of the cost expenditure in achieving all the goals of this Master Plan. 5.2.3 Implementation To be effective, the preferred alternative for each major basin must be implementable as development occurs, or in a sequence that allows the improvements to fully function as designed after they are constructed, so benefits are immediately realized and the adverse impacts to the watershed are controlled. This drives project phasing recommendations. If a developer is dependent on improvements disconnected from the site to mitigate impacts, other requirements may be placed on the developer to control stormwater release rates. The overall purpose of this Master Plan is to propose mitigation for flood impacts, which can be implemented cost effectively and sequentially by Aspen, various stakeholders, and individual developers. The proposed solutions are conceptual. Alterations to this plan can be made, but should not reduce the effectiveness for flood control. 5.3 CONCEPTUAL ALTERNATIVES Basic flood control concepts considered for each basin are listed in Table 5.1. The Conveyance alternative consists of releasing all stormwater runoff without any new detention. This alternative would require that culverts and storm sewer outfalls in the study reaches be sized to convey the estimated peak flows. Detention can be used to reduce stormwater flows from upstream areas in the watersheds, and the Detention alternative examines this scenario for potential detention sites in each watershed (if possible) where existing downstream infrastructure does not have adequate capacity or to minimize proposed storm system costs downstream. P144 I. April 2015 5-3 | Alternative Development Table 5.1 Basic Flood Control Alternatives Major Basin 5-year Detention 10-year Detention 5-year Conveyance 10-year Conveyance Hunter Creek Basin X Gibson Avenue Basin X X Neale Avenue & OK Flats Basin X X Riverside McSkimming Basin X X Eastwood Basin X Stillwater Bridge Basin X 5.3.1 Detention For this alternative, two potential detention pond areas were identified in the Gibson Avenue Basin and the Neale Avenue & OK Flats Basins and where iteratively sized within the space available to attempt to alleviate peak flows further downstream. The Gibson Avenue Basin proposed detention area is located at storage P01-G03ALT (See Figure 2.3) where there is an existing underground infiltration basin facility in place. This proposed detention area is approximately 6.5 feet deep with a footprint equal to approximately 0.16 acres. The Neale Avenue & OK Flats Basin proposed detention area is located south of Park Circle road in an existing open field at storage P04-N15ALT, just north of the Smuggler Racquet Club. This proposed detention pond was conceptually sized to be 10 feet deep with a maximum surface area of approximately 0.25 acres based on the space available. Characteristics and performance metrics for the sub-regional detention pond alternatives are summarized in Table 5.2. Both of these detention alternatives require easements for the proposed piped storm sewer system. No water quality capture volume (WQCV) was considered in the development of these detention alternatives. Table 5.2 Proposed Detention Pond Effectiveness Pond ID Name (State ID) Capacity1 (ac-ft) Pond Inflow Q100 (cfs) Pond Outlet Discharge (cfs) Peak Reduction (%) Maximum HGL (ft) Gibson Avenue Basin P01- G03ALT Williams Ranch Detention (previous underground infiltration basin) 0.47 13.2 12.0 16 7973.4 Neale Avenue & OK Flats Basin P04- N15ALT Smuggler Racquet Club Floodwater Detention Reservoir (Add skirting berm and outlet) 0.55 17.4 17.0 2 7966.0 Notes: 1Available flood control volume to the proposed pond crest. % = percent; ac-ft = acre feet; cfs = cubic feet per second; HGL = hydraulic grade line; ID = identification P145 I. 5-4 | Alternative Development April 2015 5.3.2 Conveyance For this alternative, culverts and storm system networks are sized for either the 5- or 10-year events using existing conditions land use. No new on-site or regional detention is proposed for conveyance alternatives. Overflow from existing or proposed systems are contained in the rural or urban roadway cross section, where available capacity is estimated based on the capacity of the standard roadway cross sections shown in Aspen’s Design Standards. An 18-inch reinforced concrete pipe (RCP) is the smallest proposed storm conveyance structure recommended in each basin’s alternative analysis. In many instances, with the exception of the alternatives proposed for the Riverside McSkimming Basin, the minimum proposed 18-inch RCP size was adequate to convey the 10-year event, eliminating the 5-year event alternative. To evaluate the “Minimal or Without Easements” scenario, conveyance alternatives for the Gibson Avenue and Neale Avenue & OK Flats Basins were combined to keep the proposed storm sewer system alignments within the road right-of-way. This was also done for the Eastwood and Stillwater Bridge Basins. The “With Easement” scenario was also evaluated on these combined basins for comparison. 5.3.3 Easements Several alternatives required easements on private land for the proposed storm sewer system alignments. Each of these locations are shown on Figures 5.1, 5.2, 5.3, and 5.4 for the Hunter Creek Basin, Combined Gibson Avenue and Neale Avenue & OK Flats Basins, Riverside McSkimming Basin, and Combined Eastwood and Stillwater Bridge Basins, respectively, and are discussed in the subsequent sections. Easement areas for certain piped sections were calculated based on criteria outlined in Chapter 12 of the City of Springfield, Missouri’s Drainage Criteria Manual (Reference 10), which provides a generalized method for estimating needed easement area. This was the only available source found that outlined, in detail, a methodology to estimate easement area extents for buried storm pipe based on depth and pipe size. The criteria states that if the depth of the pipe is less than 4 feet deep, the minimal easement width of 10 feet should be used. If the pipe depth is greater than 4 feet, the pipe diameter was summed with median pipe depth multiplied by 2, plus an additional foot to determine the easement width. The final calculated easement width was multiplied by the pipe length in the easement area and multiplied by estimated land cost per square foot. Land parcel cost data obtained from Aspen (2012) was used to estimate the cost per square foot. 5.4 STORMWATER ALTERNATIVES Alternative plans examined for each basin in the study area are described in the following paragraphs. Alternatives suggested for implementation based on least construction costs that still achieve conveyance goals are illustrated schematically on Figures 5.1, 5.2, 5.3, and 5.4 for the Hunter Creek Basin, Combined Gibson Avenue and Neale Avenue & OK Flats Basins, Riverside McSkimming Basin, and Combined Eastwood and Stillwater Bridge Basins, respectively, at the end of this section. Hydraulic performance for each alternative is summarized in Table 5.3. The supporting analysis for each alternative is included in Appendix E. P146 I. April 2015 5-5 | Alternative Development 5.4.1 Hunter Creek Basin 5-Year Detention Alternative: No detention sites were identified in the Hunter Creek basin because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 10-Year Detention Alternative: No detention sites were identified in the Hunter Creek basin because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 5-Year Conveyance Alternative: Currently, there is no existing system within the Hunter Creek basin. The recommended minimum storm sewer (18-inch RCP) was estimated to be able to convey the 10-year event; therefore, the need to for a 5-year conveyance alternative was eliminated. 10-Year Conveyance Alternative: An 18-inch RCP storm sewer system is proposed beginning at D06-H03 to run along Spruce Street, curve to the west at Williams Way, and outfall to an existing ditch as Williams Way turns to the north. The storm flows will then continue in the existing ditch through undeveloped, wooded areas to discharge into Hunter Creek. The proposed system running along Spruce Street will capture upstream runoff within the basin, alleviating flooding at the known flooding areas at the intersection of Spruce Street and Spruce Court and further south along Spruce Street, and was estimated to be able to convey up to the 100-year event. This improvement only affects a single property with known flooding issues and will require an easement for construction. Therefore, this proposed improvement will be tied to future improvements and/or development on that property. 5.4.2 Gibson Avenue Basin 5-Year Detention Alternative: Using the minimum recommended 18-inch RCP for proposed storm sewer improvements coupled with the maximum amount of attenuation possible within the available existing detention area at P01-G03, the proposed downstream storm sewer system is able to convey the 10-year event which eliminated the need for a 5-year detention alternative. 10-Year Detention Alternative: A conceptual detention pond located upstream of Teal Court in the area of the current underground seepage basin on Williams Ranch (P01-G03ALT) was evaluated and found to attenuate the 10-year event without overtopping. To form the detention pond, a 2.5-ft berm with 4h:1V side slopes is proposed adjacent to the Teal Court parking lot, along with removal of the current underground seepage system and excavation of the area to yield approximately 0.27 ac-ft of detention to the spillway and 0.47 ac-ft to the pond crest. The total depth of the detention pond is 6.5 feet to the pond crest and 5 feet to the spillway crest. A 3-inch rectangular orifice outlet structure was sized iteratively in the InfoSWMM model. During the 100-year event, this pond and outlet configuration would overtop the spillway by approximately 0.4 feet (approximately 11 cfs). The pond offers minimal attenuation during the 100-year event but attenuates the 10-year event from approximately 4 cfs to 0.7 cfs, yielding a 10-year event peak reduction of approximately of 83 percent. The detention pond and piping network through the Teal Court parking lot will require a private easement. Although the proposed Gibson Avenue Basin detention pond offers a high percent reduction in peak flow during the 10-year event, these flows are still relatively low and do little to minimize peak flows further downstream along Lone Pine Road. P147 I. 5-6 | Alternative Development April 2015 With the proposed detention pond, there are still a number of conveyance improvements needed to be able to convey runoff from 10-year storm event to the Roaring Fork River without possible flooding within the Gibson Avenue Basin. A 24-inch RCP storm sewer is proposed from D03- G02 to the proposed detention pond. From the detention pond, the 3-inch rectangular orifice outlet structure discharges to an 18-inch RCP storm sewer system that runs through the Centennial Condominiums common area to Spruce Street. The 18-inch system continues along Spruce Street until it curves to the east, to Walnut Street, turns north and drains along Lone Pine Road. Two 18-inch storm sewers are proposed at G05 and G13. The G05 storm sewer is proposed to collect upstream runoff currently routed to an existing undersized cross-culvert. The G13 storm sewer is proposed to collect street runoff along Lone Pine Road from the intersection of the cross culvert and the proposed 18-inch RCP storm system to D27-G06, where the system is proposed to be upsized to a 24-inch RCP system that ties into the existing 24-inch CMP that outfalls to the Roaring Fork River at OFALL-1. A separate, 18-inch RCP storm sewer is proposed to collect runoff and ditch flow at the River Bluff Townhomes and tie into the proposed Lone Pine Road system at the parking lot entrance. 5-Year Conveyance Alternative: The Gibson Avenue Basin was combined with the Neale Avenue & OK Flats Basin to minimize cost and easement locations for the conveyance alternative. The recommended minimum 18-inch RCP storm sewer was estimated to be able to convey the 10-year event; therefore, the need for a 5-year conveyance alternative was eliminated. 10-Year Conveyance Alternative: The 10-year conveyance alternative for the Gibson Avenue Basin was combined with the Neale Avenue & OK Flats Basin to minimize cost and easement locations. The combined conveyance alternative for these two basins is described in Section 5.4.4. 5.4.3 Neale Avenue and OK Flats Basin 5-Year Detention Alternative: Using the minimum recommended 18-inch RCP for proposed storm sewer improvements coupled with the maximum amount of attenuation possible within the available detention area at P04-N15ALT, the proposed downstream storm system can convey the 10-year event which eliminated the need for a 5-year detention alternative. 10-Year Detention Alternative: A conceptual detention pond located on the south side of Park Circle on the undeveloped northern portion of the Smuggler Racquet Club parcel (P04-N15ALT) was evaluated and found to attenuate the 10-year event without overtopping. The detention pond is comprised of a berm with 4H:1V sides slopes proposed to skirt around the southwest corner of the area coupled with some excavation to yield approximately 0.32 ac-ft to the spillway and 0.55 ac-ft to the pond crest. The total depth of the detention pond is 7 feet to the pond crest and 5.25 feet to the spillway crest. A 2-inch orifice outlet structure was sized iteratively in the InfoSWMM model. During the 100-year event, this pond would overtop the spillway by approximately 0.7 feet (approximately 17 cfs). The pond offers no significant attenuation during the 100-year event but attenuates the 10-year event from approximately 3.1 cfs to 0.2 cfs, yielding a 10-year event peak reduction of approximately 94 percent. Although the proposed Neale Avenue & OK Flats Basin detention pond offers a high percent reduction in peak flow during the 10-year event, these flows are still relatively low and do little to minimize peak flows further downstream along Park Circle. With the proposed Smuggler Racquet Club detention pond, there are still a number of conveyance improvements needed to be able to convey runoff from 10-year storm event to the P148 I. April 2015 5-7 | Alternative Development Roaring Fork River without possible flooding within the Neale Avenue & OK Flats basin. An 18-inch RCP storm sewer is proposed to begin at N11 on Silverlode Drive that collects runoff to the intersection of Park Circle and then runs under Park Circle to the proposed Smuggler Racquet Club detention pond. The 2-inch orifice outlet structure discharges into a downstream 18-inch storm sewer system that runs back to and parallel Park Circle to J17-N17 at the intersection of Park Circle and Brown Lane. A separate proposed storm sewer originates at the intersection of Brown Lane and Nicholas Lane where an 18-inch RCP is proposed southwest of the intersection of Brown Lane at D15-N12 to existing inlets on either side of the road, just before the intersection with Park Circle. The existing dual inlet system is proposed to be reconnected with an 18-inch RCP to the confluence with the Park Circle system. It was unclear whether this existing storm sewer was originally connected to the private underground detention tank under the Centennial Condominiums to the west. The proposed system is assumed to not be connected to the underground tank and to continue parallel to Park Circle with an 18-inch RCP to the intersection with Gibson Avenue where the system crosses private property onto East Francis Street and will require an easement. The system continues in 24-inch RCP on East Francis Street to D20-N25 where it continues along the road and through another private property area until it outfalls to the Roaring Fork River at OFALL-6. A separate 18-inch storm system is proposed along King Street that will connect to the Neale Avenue storm system at the King Street and Neale Avenue intersection to alleviate a known flooding area. The stretch along Neale Avenue from Gibson Avenue to Queen Street is proposed to be replaced by 36-inch RCPs to accommodate the incoming proposed storm sewer system from King Street. All other existing pipe sections were estimated to be able to convey the 10-year event. 5-Year Conveyance Alternative: The Neale Avenue & OK Flats Basin was combined with the Gibson Avenue Basin to minimize cost and easement locations for the conveyance alternative. The recommended minimum 18-inch RCP storm sewer was estimated to be able to convey the 10-year event; therefore the need for a 5-year conveyance alternative was eliminated. 10-Year Conveyance Alternative: The 10-year conveyance alternative for the Neale Avenue & OK Flats Basin Gibson Avenue Basin was combined with the Gibson Avenue Basin to minimize cost and easement locations. The combined conveyance alternative for these two basins is described in Section 5.4.4. 5.4.4 Combined Gibson Avenue and Neale Avenue & OK Flats Basins Conveyance Alternatives To simplify the conveyance alternatives and minimize proposed storm sewer construction and required easements, the Gibson Avenue and Neale Avenue & OK Flats Basins were combined into one alternative. The following sections describe each alternative in detail. 5-Year Conveyance Alternatives: The recommended minimum 18-inch RCP storm sewer was estimated to be able to convey the 10-year event; therefore, the need for 5-year conveyance alternatives for the combined Gibson Avenue and Neale Avenue & OK Flats Basins was eliminated. P149 I. 5-8 | Alternative Development April 2015 10-Year Conveyance Alternative (With Minimal Easements): For the 10-year conveyance alternative with minimal easements, the combined Gibson Avenue and Neale Avenue & OK Flats Basin model redirected flow from the upper reaches of the Gibson Avenue Basin to Park Circle. The upper existing storm sewer systems collecting runoff from sub-basins G01, G02, and G03 are allowed to flow into the existing underground seepage facility at P01-G03ALT and several in-line dry wells. During a significant storm event (the 25-year event or greater), runoff overflows this seepage area and spills into the Teal Court parking lot where the proposed storm sewer system begins. An 18-inch RCP storm sewer system is proposed to begin in Teal Court at D25-G05 and will require an easement along the proposed alignment until the intersection with Williams Ranch Court. The system continues down Brown Lane where it intersects with the proposed Park Circle system. This reach is known as the Brown Lane Branch in Table 5.3. The proposed system along Park Circle, known as the Main Gibson Avenue Basin and Neale Avenue & OK Flats Combined Main Stem in Table 5.3 begins at N11 as an 18-inch RCP along Silverlode Drive. The proposed piped network then heads downhill where it takes a sharp turn toward the northwest along Park Circle. After connecting with the Brown Lane Branch, the system continues down Park Circle as an 18-inch RCP it takes a turn down Gibson Avenue and is upsized to a 24-inch RCP at D34-G07. The final reach of the combined main stem continues down Gibson Avenue as a 24-inch RCP to where it joins the existing outfall from a previous 24- inch CMP section at OFALL-3. A small separate 18-inch RCP storm sewer is proposed along East Francis Street in the Oklahoma Flats area. This system begins at N25 and follows East Francis Street to where it requires a private easement before discharging into the Roaring Fork River at OFALL-6. Another separate storm sewer is proposed to replace an assumed 8-inch polyvinyl chloride (PVC) pipe that discharges into a private detention area at D08-G08. An 18-inch RCP is proposed to collect flow from the existing ditch at G08 and discharge into this private detention area. This 18-inch RCP improvement will require a private easement. The detention area was not modeled to estimate the attenuation for peak flows as it is small and has a relatively high normal pool. The detention pond overflows into an undersized 6-inch CMP but overflow is conveyed into a road side ditch along Red Mountain Road. An existing 12-inch CMP at D10- G10 collects the overflow and discharges to the Roaring Fork River at OFALL-2. This existing 12-inch CMP was shown to have 100-year capacity with this combined basin storm system. The rest of the storm sewer improvements for this combined conveyance alternative are identical to the 10-year detention alternatives for the Gibson Avenue Basin and the Neale Avenue & OK Flats Basin as described in Sections 5.4.2 and 5.4.3. All other existing piped systems were shown to be able to convey the 10-year event with this combined configuration. 5.4.5 Riverside McSkimming Basin The Riverside McSkimming Basin has four proposed alternatives. Two proposed alternatives that can convey up to the 5-year event; one with easements to minimize construction costs and one with minimal easements to minimize easements cost to the overall project. The same minimal easements and with easements scenarios are also proposed for systems that can convey the 10-year event. The following sub-sections describe these proposed alternatives in detail. P150 I. April 2015 5-9 | Alternative Development 5-Year Detention Alternative: No detention sites were identified in the Riverside McSkimming basin because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 10-Year Detention Alternative: No detention sites were identified in the Riverside McSkimming basin because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 5-Year Conveyance Alternative (With Easements): The Riverside McSkimming basin has two main proposed storm systems: the East Cooper Avenue (OFALL-06) and East Hopkins Avenue outfalls (OFALL-10). All other drainage areas in the basin were considered direct flow areas to the Roaring Fork River. The proposed East Hopkins Avenue Outfall consists of two main southern and northern storm systems. The proposed northern system begins as an 18-inch RCP starting close to the beginning of Midland Park Place at D20-R07 where it runs along Midland Avenue to the intersection for Park Avenue and Regent Street at D31-R05. An easement would be needed from D29-R07 to R07 to connect to the existing system. From this proposed system confluence, the piped system is upgraded to a 24-inch RCP. The 24-inch RCP northern system continues to the confluence with the southern system at the intersection of Park Avenue an East Hopkins Avenue at D22-R10 and then to the proposed storm sewer system outfall to the Roaring Fork River at OFALL-06. The East Hopkins Avenue southern system has two sections: one that begins as an 18-inch RCP at the beginning of Mascotte Lane at D21-R05 and the other beginning as an 18-inch RCP at the intersection of Ardmore Drive and Ardmore Court at D25-R08. The two sections meet at the intersection of Midland Avenue and Smuggler Grove Road at D35-R05 where the southern system flows to the intersection of Midland Avenue and East Hopkins Avenue. An easement is required through a private property in the southern branch from D33-R05 to D34-R05. The southern system then continues along East Hopkins Avenue to the main system confluence with the northern branch at the intersection of Park Avenue and East Hopkins Avenue at D22-R10. The aesthetic ponds in the area that contribute to this proposed system (P04-R08 and P03-R08S) were modeled as full during the simulation to be conservative with the proposed storm system capacity and provided minimal attenuation during all storm events. The proposed East Cooper Avenue storm sewer system begins at the lower end of Eastwood Drive at D06-R11 as an 18-inch RCP where it continues northwest along Eastwood Drive then cuts to the southwest through a private parcel to Highway 82 that will require an easement from D09-R09 to D10-R09. The proposed system then continues northwest along Highway 82 as a 18-inch RCP as it turns into East Cooper Avenue and outfalls to the Roaring Fork River at OFALL-10. An 18-inch RCP storm sewer is proposed at the downstream end of Lacet Lane at D16-R17 which will discharge into the main East Cooper Avenue storm sewer system at the intersection of Midland Avenue and East Cooper Avenue. All other existing evaluated systems and pipes were shown to have 5-year capacity. 5-Year Conveyance Alternative (With Minimal Easements): The 5-year conveyance alternative with minimal easements includes one piped system change within the proposed East Hopkins Avenue proposed storm system relative to the scenario with easements. The south system at D33-R05 is connected to the north system at D21-R05, eliminating two sections to create one large southern branch. It also eliminates the private easement and reach along Smuggler Grove Road, decreasing costs for the overall proposed alternative. The easement along the East Cooper Avenue Outfall system (D09-R09 to D10-R09) still remains for this P151 I. 5-10 | Alternative Development April 2015 option as there is no alternative route to avoid private easements in this area and still capture and convey runoff safely from private residences. All pipe sizes remain the same as the easement alternative for the 5-year event. 10-Year Conveyance Alternative (With Easements): The 10-year conveyance alternative with easements resembles the 5-year conveyance storm systems with easements with pipe size upgrades to convey the 10-year event. The proposed East Cooper Avenue storm system requires a 24-inch RCP from R19 to the systems outfall at OFALL-10. Easements are required from D29-R07 to R07, D33-R05 to D34-R05, and D09-R09 to D10-R09. All other proposed alignments and pipe sizes for the 10-year conveyance alternative with easements are identical to the 5-year conveyance alternative with easements. 10-Year Conveyance Alternative (With Minimal Easements): The 10-year conveyance alternative with minimal easements resembles the storm sewer system alignments for the 5-year conveyance alternative with minimal easements. The proposed East Cooper Avenue storm system requires a 24-inch RCP from R19 to the outfall at OFALL-10. All other proposed alignments and pipe sizes for the 10-year conveyance alternative with easements are identical to the 5-year conveyance alternative with minimal easements (as a single easement from D09-R09 to D10-R09). All other proposed storm system alignments and existing pipes were shown to have 10-year capacity. 5.4.6 Combined Eastwood and Stillwater Bridge Basins Conveyance Alternatives The Eastwood and Stillwater Bridge Basins were combined to minimize private easements and construction costs. Each alternative has a scenario that either contains private easements to minimize construction and itemized costs or eliminates easements to minimize the overall costs for the alternative. The following sub-sections describe each alternative in detail. 5-Year Detention Alternative: No detention sites were identified in either of the Eastwood or Stillwater Bridge basins because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 10-Year Detention Alternative: No detention sites were identified in either of the Eastwood or Stillwater Bridge basins because no undeveloped land was available within the basin with sufficient area to provide effective storm runoff flow attenuation or water quality benefits. 5-Year Conveyance Alternative: The recommended minimum 18-inch RCP storm sewer was estimated to be able to convey the 10-year event; therefore, the need for 5-year conveyance alternatives for the combined Eastwood and Stillwater Bridge Basins was eliminated. 10-Year Conveyance Alternative (With Easements): The combined Eastwood and Stillwater Bridge Basins 10-year conveyance alternative with easements is mainly comprised of two separate proposed storm sewer systems: The Stillwater Bridge Basin storm system and the Eastwood Basin storm system. The proposed Stillwater Bridge storm system consists of a main stem and a south system. The main stem starts at D13-S03 along Mountain Laurel Drive as an 18-inch RCP. The system heads to the north, following Mountain Laurel Drive until it intersects with West Lupine Drive and follows West Lupine Drive south. At the intersection of Lupine Drive and East Lupine Drive the alignment turns toward the southwest down Lupine Drive where at Highway 82 (S09) the pipe system is upsized to a 24-inch RCP and jacked under the highway to D19-S10. The final reach requires a private easement to outfall to the Roaring Fork River at OFALL-3. The south system begins at D02-S06, on the other side of a high point along Mountain Laurel Drive and heads to the south, following the road as an 18-inch RCP. The south P152 I. April 2015 5-11 | Alternative Development system follows Mountain Laurel Drive until D03-S04 where the alignment crosses a private easement to meet East Lupine Drive to the west. The system then runs north along East Lupine Drive where it turns to the west at D06-S10 to cross a private easement to join with the main stem at D07-S10, just before crossing Highway 82. The Eastwood Basin proposed storm system begins just downstream of the intersection of Northway Drive and Westview Drive at D12-E02 as an 18-inch RCP. The proposed system then heads south along Northway Drive where it turns toward the east along Roaring Fork Drive and follows the road until Highway 82. At Highway 82 (D18-E02) the pipe size is increased to a 24- inch RCP before being jacked underneath the highway and directed toward the intersection of Stillwater Drive. The final reach of the proposed storm system follows Stillwater Drive until discharging downstream of the bridge at OFALL-01. 10-Year Conveyance Alternative (With No Easements): This combined Eastwood and Stillwater Bridge Basins alternative eliminates the need for any private easements to minimize costs and closely resembles the 10-year conveyance alternative with easements with a few modifications. First, the south section of the Stillwater Bridge storm system is altered at D03- S04 to continue along Mountain Laurel Drive as an 18-inch RCP to East Lupine Drive where it turns to the northwest and continues along East Lupine Drive to D05-S07 and follows the road toward the north to Lupine Drive and joins the main stem at D31-S10. The main stem requires the storm system to be upsized to a 30-inch RCP at Highway 82 (S09) before being jacked under the highway toward Stillwater Drive where it joins the Eastwood Basin storm system at D32-E06. The final reach of combined Eastwood Basin and Stillwater Bridge Basin storm systems continues down Stillwater Drive as a 30-inch RCP before discharging into the Roaring Fork River on the downstream side of the bridge at OFALL-01. A small storm sewer collects flow along Highway 82, beginning at D07-S10 as an 18-inch RCP, and joins with the Stillwater Basin storm system main stem at S09. The Eastwood Basin storm system is identical to the 10-year conveyance easement scenario as no easements were required for this alignment. P153 I. 5-12 | Alternative Development April 2015 This page intentionally left blank P154 I. !!!!!!!!!!!!!! !!!! !!!! ! !%, %, %O %O Note: This proposed improvement affects this single property and will be obligation of the owner upon redevelopment. HunterCreek RoaringForkRiver "~ 748 ft of 18-in RCP; ~ 7 MH; 1 FES; riprap apron People have to sandbag Basement flooding in 2006 storm." ~ 68 ft long private easement for 18-in RCP Gibson Ave. Aspen Art Museum Park 7 9 7 0 7880 7950 7960 787079407860793078907910 7 9 2 079007850 7980 7990800080108020784080308040783079307 8 3 0 78507980 79007890 78907860 79407940 7 8 5 0 7900 79507880786079107 8 8 0 7840 7930 7 8 3 0 7840 78307840784079007960 7 8 4 0 78707910 797078907890 8 0 3 0 7 8 9 0 7950797079307880 7 9 2 0 7 8 4 07890 7 9 1 07840 7940 7940 7880 7 9 2 0 7920 78407 9 3 0 79007 9 3 0 7960SalvationM o c k l i n M o c k l i n Mocklin M o ck lin Hunter Creek Basin Hunter Creek Basin H03 H05 H02 H04 H01 REDMTNRDSPRUCESTLONEPINERD VINESTGIBSONAVE TEALCTNMILLSTSPRUCECTRACESTBROWNLNS H A D Y L N PUPPYSMI THSTNSPRI NGSTCOWENHOVENCTWALNUT STINDEPENDENCEPL BRENDENCTOFALL-13 OFALL-12 H04 D16-H03 D12-H03 D11-H03 D10-H03 D09-H03 D08-H03 D06-H03 H02 H05 H03 H01 J02-H03 OFALL-11 0 200 Feet o 10-year Hunter Creek Basin Conveyance Alternative Smuggler/Hunter Surface Drainage Master Plan 5.1 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig5-01 Hunter Alternativer90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Conduit Overflow Legend %,Known Deficiencies %O Potential Water Quality Locations Proposed Improvements Easement Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water Existing 100-yr Floodplain P155I. !!!!!!!!!!!!!!!!!! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! ! ! ! !!!%, %, %, %, %, ?> ?> UT ^_ ^_ ^_ %O %O %O %O %O SOUTH AVE "~270 ft long private easement for 18-in RCP RoaringForkRiver GIBSONAVE PARKCIREHOPKINSAVE SMUGGLERMTNRDSPRUCESTSILVERLODEDROAKLNLONEPINERD PARKAVENSPRINGSTNEALEAVE VINEST SSPRINGSTEMAINST KINGSTMAPLELNRACEST SORIGINALSTTEALCTAJAXAVEMIDLANDAVENI CHOLAS LN QUEEN STWALNUTST COTTONWOODLNRIOGRANDEPL WILLIAMSRANCHDRWILLIAMSWAYMASCOTTE LN BAYST FREESI LVERCTCOWENHOVENCTEFRANCISST EBLEEKERST MATCHLESSDRHAROLDROSSCTREGENTSTBRENDENCTNSPRINGSTPeople have to sandbag Dry well plugged and floods System needed to drain low spot Basement flooding in 2006 storm. Snowmelt flooding. Localized flooding. No outlet. N26 N16 N06 N03 N01 G03 J20-12 J22-N23 J19-N12 J14-N12 J13-N12 J12-N12 J11-N10 J10-N10 J09-N10 J08-N10 J07-N05 J06-N10 J04-N05 J03-N09 J06-G10 J01-G06 J21-N23 N24 N23 N21 N20 N19 N18 N17 N15 N14 N13 N11 N10 N09 N08 N07 N05 N04 N25 G13 G11 G08 G12 G10 G05 G07 G06 G04 G02 G01 D2-N12J18-N17 J17-N17 D26-N23 D25-N22 D23-N13 D22-N13 D22-N04 D18-N17 D17-N17 D16-N17 D15-N12 D14-N12 D11-N21 D10-N21 D09-N21 D08-N21 D07-N21 D06-N26 D05-N21 D04-N20 D03-N19 D01-N06 D01-N02 D25-G05 D24-N13 D34-G07 D33-N17 D32-G05 D27-G06 D26-G06 D25-G06 D24-G06 D12-G03 D10-G10 D09-G10 D08-G08 D08-G10 D07-G09 D06-G02 D05-G02 D03-G02 N22 N12 N02 G09 D21-N25 D13-N23 D12-N23 D30-G08 D02-G02 P03-N16 P02-N01 DW07-G03 DW04-G03 DW02-G04 DW01-G04 DW06-G03 DW05-G03 DW08-G03 DW03-G03 P01-G03ALT"~245 ft long private easement for 18-in RCP "~1023 ft of 18-in RCP; 7 MHs "~1115 ft of 18-in RCP; 7 MHs; Pipe intake "~2567 ft of 18-in RCP; 15 MHs"~960 ft of 24-in RCP; 7 MHs; 1 FES "~542 ft of 36-in RCP; 2 MHs"~374 ft of 18-in RCP; 2 MHs; 1 FES "~283 ft if 18-in RCP; 2 MHs"~245 ft of 18-in RCP; 0 MHs; 1 FES; Pipe intake OFALL-8 OFALL-7 OFALL-6 OFALL-2 OFALL-5 OFALL-4 OFALL-3 OFALL-1 OFALL-DW Neale Avenue and OK Flats Basin Gibson Avenue Basin Gibson Ave. Herron Park Garrison Park N. Spring St. Aspen Art Museum Park Johnson Shaft Unknown Source Mollie Gibson ShaftSalvat i onAstorMoc kl i nM o c k l i n Mocklin N02 G01 G05 N01 N04 G04 N12 N20 N05 N13 N15 N25 G08 N14 N21 N17 N24 N06 N23 N19 G13 N18 G02 G06 N09 N10 N03 N22 N08 N07 G07 G09 N11 G11 N26 N16 G03 G10 G12 0 300 Feet o 10-year Combined Gibson Avenue Basin and Neale Avenue & OK Flats Basin Conveyance Alternative (With Limited Easements) Smuggler/Hunter Surface Drainage Master Plan 5.2 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig5-02 Gibson Neal Alternativer90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Dry Well ?>Pond UT Underground Storage Conduit Overflow Orifices Outlet Weirs Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Proposed Improvements Easement !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Riparian Areas Surface Water Existing 100-yr Floodplain!!!!!!!!! ! ! ! ! ! ! !!!!!!!!?>"~270 ft long private easement for 18-in RCP "~1023 ft of 18-in RCP; 7 MHs DW07-G03 DW06-G03 DW05-G03 DW04-G03 DW03-G03 DW02-G04 DW01-G04 P01-G03ALT DW08-G03 G04 G02 G01D25-G05 D12-G03 D06-G02 D05-G02 D03-G02 D02-G02 OFALL-DW79807990 8000801079708020 803080408 0 1 0 80108010J01-G06 Sal vat i onSILVERLODEDR TEALCTWILLIAMSRANCHDRG05 G02 G04 G03 G01 G03 P156I. !!!!!!! ! ! ! ! ! !!!%, %, %, ?> ?> ?> ?> ^_%O %O %O ECOOPERAVE PARKAVEMCSKI MMI NGRDSWESTENDSTUTEPLMIDLANDAVEEASTWOOD DR KINGST WESTVIEW DR WATERSAVE SKIMMINGLNROARING FORK DRARDMOREDR WLUPI NEDRNORTHWAYDRRIVERSIDEDRSRIVERSIDEAVEASPEN GROVE RD QUEENST CLEVELANDSTCRYSTALLAKERDFREDLNMASCOTTELN DALEAVE ARDMORECTALICELNALPINE CTNRIVERSIDEAVELACETCT EHOPKINSAVE EHYMANAVE System needed in area Dry well plugged and floods " ~2006 ft of 18-in RCP; 11 MHs " ~1416 ft of 8-in RCP; 8 MHs"~799 ft of 18-in RCP; 6 MHs "~318 ft of 24-in RCP; 3 MHs; 1 FES "~218 ft of 24-in RCP; 1 MH; 1 FES "~68 ft of Jacked 18-in RCP; 1 MH"~57 ft of Jacked 18-in RCP; 1 MH"" ~205 ft long private easement for 18-in RCP R04 R03 R02 R01 R14 R17 R12 R18 R20 R13 R05 R10 R08 R09 R06 R15 J25-R05 J20-R19 J18-R05 J17-R08 R19 R11 D36-R07 D35-R05 D33-R05 D32-R05 D31-R05 D30-R05 D29-R07 D28-R05 D27-R05 D26-R05 D25-R08 D24-R08 D22-R10 D21-R05 D20-R07 D17-R19 D16-R17 D15-R19 D14-R04 D13-R19 D12-R19 D11-R09 D10-R09 D09-R09 D08-R11 D07-R11 D06-R11 D05-R19 D23-R10 P02-R13 P01-R15 P03-R08S P04-R08N DW01-R07 Snyder Park Herron Park Garrison Park Unknown Source RoaringForkRiver8110809081208100 8080 8070 8130 8 06 080 4 0 805080308020 8140815081608010800081707990 8180819079708200821082208230824079608250 8260 8270 8280829083008310 832083307950 83408350 8360 8370 8380 83908400841084208430 794084408450846084708480 7980849085008510 852085307930854085507910 7 9 2 0 8 5 6 0 7900 857085807890859086008610 862086308640 7880 80108 01 0 8010 855079207950 7950 79908030 7980 7950 7970 793 0 8000 7930 79408140 81608010798079408000 8150 8060 8000 808079707940 8010 859085708030 8 0 2 0 8 0 3 0 80007960 85408050 7980 79908000 7960 8 1 2 0 8040 7980 8020 7950811080008070 80107 9 8 0 805080607960 80308 6 0 07930 7990 8 0 0 080007940 8170 80208010 8150 8180858079 50 809079808060 7980 802081407950 8 0 0 0 7940 7 9 8 0 81208010 7990 8030 8020 7 9 6 0 80007940 806079407930Salvat i onRiversideDitchAstor Riverside McSkimming Basin R04 R01 R05 R02 R08 R13 R11 R09 R19 R07 R10 R16 R03 R14 R15 R12 R06 R17 R20 R18 OFALL-14 OFALL-10 OFALL-09 OFALL-08 OFALL-07 OFALL-06 OFALL-DW01-R07 0 300 Feet o 10-year Riverside McSkimming Basin Conveyance Alternative (With Limited Easements) Smuggler/Hunter Surface Drainage Master Plan 5.3 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig5-03 Riverside Alternativer90.mxd Plot Date: 3/31/2015 InfoSWMM Elements Junction Divider Outfall Dry Well ?>Pond Conduit Overflow Orifices Weirs Legend %,Known Deficiencies %O Potential Water Quality Locations ^_Mine Flow Sources Proposed Improvements Easement Topographic Contour Interval = 10 feet !!Irrigation Ditch, Culvert Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water Existing 100-yr Floodplain P157I. RoaringForkRiver HWY82MTNLAURELDREASTWOODDR WESTVIEW DR ROARING FORKDR NORTHWAYDRSTILLWATERLN STILLWATERDRASPEN GROVE RD FABILOOPMTNLAURELCTMCSKIMMINGRD CRYSTALLAKERDMCSKIMMING RD ALICELNLUPINEDRWLUPINEDRELUPI NEDR" ~3468 ft of 18-in RCP; 19 MHs " ~2833 ft of 18-in RCP; 13 MHs"~917 ft of 18-in RCP; 4 MHs "~382 ft of 30-in RCP; 4 MHs; 1 FES "~202 ft of 24-in RCP; 3 MHs "~161 ft of Jacked 30-in RCP; 0 MH"~171 ft of Jacked 24-in RCP; 0 MH E05 E02 S09 S08 D34-E06 D33-E06 D32-E06 D31-S10 D30-S10 D20-E03 D25-S04 D24-S04 D23-S04 D22-S04 D21-S04 D22-E02 D21-E02 D20-E02 D19-E02 D17-E02 D16-E02 D15-E02 D14-E02 D12-E02 D11-E02 D10-E02 D09-E04 D08-E04 D07-E04 D06-E03 D18-S08 D17-S08 D16-S04 D15-S04 D14-S01 D13-S03 D12-S08 D11-S02 D08-S02 D07-S10 D06-S10 D05-S07 D03-S04 D02-S06 D01-S05 D18-E02 E04 E03 E01 S02 S12 S10 S11 S04 S07 S06 S05 S01 S03 J09-E05 OFALL-2 OFALL-1 OFALL-01 OFALL-02 8070 808080908100 8 06 0 81108040 8050 8120813081408150 81608170819082108200 8180 82208230824082508260827082808290830083108330834083508360 8370838083908400841084208430 84408450846084708480 8490 8500851085208530832085408550856085708020 858085908000803086307 9 9 0 8640865086608670868086008010 86108620869087008710 80508 0 6 0 8140 86608010 8020 811081408150 803080308040 8040 8120 80508060 8 0 7 0 8690801086107990 839081608010 80807990 8150 8040804086508020 818079908080809081208630812080708 0 4 0 8050 8 0 0 0 8 0 6 0803 0869081108 0 2 0 80408 1 3 0 8 0 2 0 8400801080908000 8020809080408 0 0 0 86208080 8380869084108 1 2 0 8030 86408 1 0 0 805086008040 8 0 1 0 8010 805 0803080408040 81608030 8120815086408060 8060 8120837081908 0 4 0 80208050 8140 8060 S a l v a t i o n Eastwood Basin Stillwater Bridge Basin E02 S01 S03 E04 E03 S08 S04 S05 E06 S07 S10 E05 S09 E01 S06 S12 S02 S11 0 300 Feet o 10-year Combined Stillwater Bridge Basin and Eastwood Basin Conveyance Alternative (Without Easements) Smuggler/Hunter Surface Drainage Master Plan 5.4 T:\Projects\22242939_Aspen_Smuggler_MP\Sub_00\7.0_CAD_GIS\7.01_GIS_Maps\2015-01 Revised 90pct Submittal\Fig5-04 Stillwater Eastwood Alternativer90.mxd Plot Date: 4/8/2015 InfoSWMM Elements Junction Divider Outfall Conduit Overflow Legend Proposed Improvements Topographic Contour Interval = 10 feet Irrigation Ditch, Open Study Area Boundary Sub-basins Major Basins Wetland Areas Surface Water Existing 100-yr Floodplain P158I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year D06-H03 C11-H03 O11-H03 Spruce St.18" RCP; 66 ft 55.5 Local 23 0.1 0.2 0.5 1.5 1.9 9 D16-H03 C20-H03 O20-H03 Spruce St. & Spruce Ct.18" RCP; 131 ft 55.5 Local 24 0.1 0.2 0.5 1.5 1.9 9 D09-H03 C13-H03 O13-H03 Spruce St.18" RCP; 111 ft 55.5 Local 26 0.1 0.2 0.5 1.5 1.9 9 D08-H03 C14-H03 O14-H03 Spruce St.18" RCP; 74 ft 55.5 Local 25 0.1 0.2 0.5 1.5 1.9 9 D10-H03 C15-H03 O15-H03 Spruce St. & Williams Way 18" RCP; 196 ft 55.5 Local 25 0.1 0.2 0.5 1.5 1.9 9 D11-H03 C16H03 O16-H03 Williams Way 18" RCP; 139 ft 55.5 Local 18 0.1 0.2 0.5 1.5 1.9 9 D12-H03 C17-H03 O17-H03 Williams Way 18" RCP; 67 ft 69.0 Local 19 1.3 2.0 2.9 5 7 16 J02-H03 C18-H03 -Existing ditch to Hunter Creek Ditch/swale 69.0 --1.3 2.0 2.9 5 7 16 H02 C19-H02 -End of Spruce Ct.Overland runoff 8.7 --0.1 0.2 0.4 0.8 1.2 2.3 OFALL-11 --Williams Woods Outfall Outfall 77.7 --1.4 2.0 3.0 6 8 18 H05 C58-H05 -Overland runoff Swale 11.5 --7 10 12 16 19 22 OFALL-12 --Hunter Creek Development Outfall Outfall 11.5 --7 10 12 16 19 22 H04 C59-H04 O59-H04 Red Mountain Road Bridge Inlet 12" CMP 3.0 Local 5 1.8 2.3 2.8 3.7 4.4 5 OFALL-13 --Red Mountain Road Bridge Outfall Outfall 3.0 --1.8 2.3 2.8 3.7 4.4 5 * Storm system capacity determined using StormCAD. Design Point Summary Table Hunter Creek Basin 10-yr Conveyance Alternative Contributing Area (ac) Road Classification Capacity *(cfs) Conduit IDSWMM Element ID Location Existing & Proposed Structures Description Overflow ID Flow Rates (cfs) Green = Sufficient Capacity Red Mountain Road Outfall (H) Hunter Creek Development Outfall Williams Woods Proposed System Page 1 of 11 P159I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year G08 C58-G08 O58-G08 River Bluff Townhome Intake 18" RCP; 57 ft 5.4 -10 2.8 3.7 5 6 7 9 D28-G08 C59-G08 O58-G08 River Bluff Townhomes 18" RCP; 124 ft 5.4 -10 2.8 3.7 5 6 7 9 D29-G08 C60-G08 O60-G08 River Bluff Townhomes 18" RCP; 173 ft 5.4 -12 2.8 3.7 5 6 7 9 G01 C01-G01 O01-G01 Williams Ranch Dr. (East)24" RCP 12.3 Local 30 1.3 1.8 2.5 4.1 5 8 D02-G02 C02-G02 O02-G02 Williams Ranch Dr. (East)24" CMP 12.3 Local 49 1.3 1.8 2.5 4.1 5 8 G02 C05-G02 O05-G02 Silverlode Dr. (Center)24" RCP 2.6 Local 25 0.6 0.7 0.9 1.4 1.7 2.2 D05-G02 C04-G02 O04-G02 Silverlode Dr. (Center)24" CMP 2.6 -58 0.6 0.7 0.9 1.4 1.7 2.2 D06-G02 C03-G02 O03-G02 Silverlode Dr. (Center)24" CMP 2.6 -30 0.6 0.7 0.9 1.4 1.7 2.2 D03-G02 C35-G03 O35-G03 Williams Ranch Parcel 24" RCP; 118 ft 14.9 Local 45 1.8 2.5 3.4 6 7 10 G04 C32-G04 O32-G04 Silverlode Dr. (West Branch)18" RCP; 33 ft 12.6 Local 20 0.2 0.4 0.6 1.3 1.6 3.1 D10-G04 C33-G04 O33-G04 Silverlode Dr. (West Branch)18" RCP; 42 ft 12.6 Local 17 0.2 0.4 0.6 1.3 1.6 3.1 D11-G04 C36-G05 O32-G05 Silverlode Dr. (West Branch)18" RCP; 122 ft 12.6 -22 0.2 0.4 0.6 1.3 1.6 3.1 D13-G05 C37-G03 O37-G03 Silverlode Dr. (West Branch)18" RCP; 123 ft 12.6 -30 0.2 0.4 0.6 1.3 1.6 3.1 P01-G03ALT C66-G03 WEIR01-G03 Proposed Detention (0.47 ac-ft); 3"Orifice 18" RCP; 40 ft 28.1 -6 2.5 3.3 4.4 7 9 13 D12-G03 C38-G05 O38-G05 Teale Ct.18" RCP; 215 ft 28.1 -25 0.6 0.6 0.7 4.1 6 12 D14-G05 C39-G05 O39-G05 Centennial Building's common grounds 18" RCP; 105 ft 28.1 -21 0.6 0.6 0.7 4.1 6 12 D15-G05 C48-G05 O48-G05 Spruce St.18" RCP; 263 ft 28.1 Local 16 0.6 0.6 0.7 4.1 6 12 D16-G05 C47-G05 O47-G05 Stpurce St.18" RCP; 116 ft 28.1 Local 13 0.6 0.6 0.7 4.1 6 12 D17-G05 C46-G05 O46-G05 Spruce St.18" RCP; 231 ft 28.1 Local 13 0.6 0.6 0.7 4.1 6 12 D18-G05 C45-G05 O45-G05 Race St. & Spruce St.18" RCP; 254 ft 28.1 Local 20 0.6 0.6 0.7 4.1 6 12 D19-G13 C44-G13 O44-G13 Private Dr.18" RCP; 159 ft 28.1 Local 23 0.6 0.6 0.7 4.1 6 12 D20-G13 C43-G13 O43-G13 Walnut St.18" RCP; 158 ft 28.1 Local 11 0.6 0.6 0.7 4.1 6 12 D21-G13 C50-G06 O50-G06 Lone Pine Rd. & Walnut St.18" RCP; 178 ft 28.1 Local 15 0.6 0.6 0.7 4.1 6 12 G13 C58-G13 O58-G13 Lone Pine Rd.18" RCP; 33 ft 2.7 Local 16 0.8 1.0 1.3 1.8 2.2 2.8 G05 C59-G05 O12-G05X Lone Pine Rd.18" RCP; 26 ft 11.5 Local 12 7 10 12 16 18 22 D30-G08 C57-G06 O57-G06 Lone Pine Rd.18" RCP; 66 ft 42.3 Local 14 8 11 13 18 21 27 D24-G06 C51-G06 O51-G06 Lone Pine Rd.18" RCP; 242 ft 42.3 Local 21 8 11 13 18 21 27 D25-G06 C52-G06 O52-G06 Lone Pine Rd.18" RCP; 279 ft 42.3 Local 23 8 11 13 18 21 27 D26-G06 C53-G06 O53-G06 Lone Pine Rd. & Vine St.18" RCP; 328 ft 42.3 Local 15 8 11 13 18 21 27 D27-G06 C54-G06 O54-G06 Lone Pine Rd. & Independence Pl.24" RCP; 141 ft 47.7 Local 30 11 15 18 23 27 32 G06 C16-G06 O16-G06 Lone Pine Rd. & Rd Mtn. Rd.24" CMP 50.1 Local 32 12 17 20 26 31 36 OFALL-1 --Lone Pine Rd. Outfall Outfall 50.1 --12 17 20 26 31 36 G07 C19-G09 O19-G09 Gibson Ave. Storm System 24" CMP 1.5 Local 29 0.5 0.7 0.8 1.2 1.4 1.8 D07-G09 C20-G09 O20-G09 Gibson Ave. Stem 18" CMP 1.5 -16 0.5 0.7 0.8 1.2 1.4 1.8 G09 C22-G09 O22-G09 Gibson Ave. Curb Inlet 12" PVC 2.9 Local 4 0.6 0.8 1.0 1.3 1.6 2.0 D08-G10 C21-G10 O21-G10 Gibson Ave. Storm Stem 18" CMP 2.9 -10 1 2 1.8 2.5 3.0 3.8 J04-G10 C29-G10 -Gibson Ave. Storm Stem Ditch 2.9 --1 2 1.8 2.5 3.0 3.8 G10 C18-G11 O18-C11 Red Mtn Rd Crossing 18" CMP 3.6 Local 15 2 2 3 3.5 4.1 5 OFALL-3 --Gibson Ave. Outfall Outfall 3.6 --2 2 3 3.5 4.1 5 G11 C17-G11 O17-G11 Bridge Curb Inlet at N. Mill St.12" CMP 0.7 Local 4 0.3 0.4 0.4 0.6 0.7 0.9 OFALL-4 --N. Mill St. Bridge Outfall (N.)Outfall 0.7 --0.3 0.4 0.4 0.6 0.7 0.9 G12 C23-G12 O23-G12 Bridge Grate Inlet at N. Mill St.12" CMP 0.2 Local 8 0.1 0.1 0.1 0.2 0.2 0.3 OFALL-5 --N. Mill St. Bridge Outfall (S.)Outfall 0.2 --0.1 0.1 0.1 0.2 0.2 0.3 * Storm system capacity determined using StormCAD. N. Mill St. Bridge Flow Rates (cfs) Green = Sufficient Capacity SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Capacity* (cfs) Conduit ID Design Point Summary Table Gibson Avenue Basin 10-yr Detention Alternative (With Easements) Overflow ID River Bluff Townhomes Branch Lone Pine Rd. Outfall Gibson Ave. Storm System Page 2 of 11 P160I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 19 0.0 0.0 0.1 0.3 0.3 2.5 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 4.2 0.0 0.0 0.1 0.3 0.4 2.8 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local -0.0 0.0 0.1 0.3 0.4 2.8 N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 7 0.0 0.0 0.2 0.4 0.6 3.8 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 --0.1 0.2 0.6 1.8 2.2 8 N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 25 0.1 0.1 0.2 0.3 0.4 0.7 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local -0.2 0.2 0.6 1.9 2.5 8 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local -0.2 0.2 0.8 2.4 3.1 12 N11 C77-N04 O77-N04 Silverlode Dr.18" RCP; 185 ft 0.7 Local 18 0.4 0.5 0.7 0.9 1.1 1.2 D22-N04 C78-N04 O78-N04 Silverlode Dr.18" RCP; 116 ft 0.7 Local 19 0.4 0.5 0.7 0.9 1.1 1.2 N04 C79-N10 O79-N10 Silverlode Dr.18" RCP; 206 ft 9.1 Local 25 1.4 1.8 2.3 3.7 4.5 6 N10 C80-N13 O12-N10 Park Cir. & Smuggler Mtn Rd. Confluence 18" RCP; 170 ft 89.3 Local 22 1.8 2.4 3.1 6 7 17 P04-N15ALT C92-N15 WEIR04-N15ALT Proposed Detention (~0.55 ac-ft); 2" Orifice 18" RCP; 160 ft 89.3 Local -1.8 2.4 3.1 5.7 7 17 D22-N13 C81-N13 O81-N13 Park Cir. & Nicholas Ln.18" RCP; 226 ft 89.3 Local 15 0.2 0.2 0.2 3.3 5.0 17 D23-N13 C82-N13 O82-N13 Park Cir.18" RCP; 215 ft 89.3 Local 14 0.2 0.2 0.2 3.3 5.0 17 N13 C91-N13 O91-N13 End of Tributary at Brown Ln.18" RCP; 40 ft 95.0 Local 17 1.7 2.2 2.6 4.0 6 20 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -35 0.0 0.1 0.3 1.0 1.3 9 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 105 0.0 0.1 0.3 1.0 1.3 9 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 12 0.2 0.3 0.4 0.6 0.7 1.0 J20-12 C34-N12 -Free Silver Ct. Roadside Ditch Ditch 60.9 --0.2 0.4 0.6 1.5 2.0 10 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local -0.2 0.4 0.6 1.5 2.0 10 D14-N12 C65-N16 O65-N16 Upstream Brown Ln & Nocholas Ln.12" PVC 60.9 Local 6 0.2 0.4 0.6 1.5 2.0 10 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.18" RCP; 178 ft 60.9 Local 24 0.2 0.4 0.6 1.5 2.0 10 N12 C28-N12 O28-N12 Brown Ln & Park Cir.18" RCP; 29 ft 6.7 Local 13 6 9 11 14 16 18 D2-N12 C67-N12 O67-N12 Brown Ln & Park Cir.18" RCP; 26 ft 67.6 Local 18 6 9 11 13 14 16 J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.18" RCP; 170 ft 163.3 Local 22 8 10 13 17 20 32 P03-N16 WEIR03-N16 -Centennial Apts. Underground Infiltration Tank 10'x80' Tank 0.6 -2 0.5 0.6 0.8 1.1 1.2 1.4 J18-N17 C68-N17 O68-N17 Park Cir.18" RCP; 240 ft 163.9 Local 21 8 11 14 18 21 33 D16-N17 C69-N17 O69-N17 Park Cir. & Spruce St.18" RCP; 75 ft 163.9 Local 18 8 11 14 18 21 33 D17-N17 C70-N17 O70-N17 South Ave. & Cottonwood Ln.18" RCP; 237 ft 163.9 Local 18 8 11 14 18 21 33 D18-N17 C71-N17 O71-N17 South Ave. & Gibson Ave.18" RCP; 89 ft 163.9 Local 14 8 11 14 18 21 33 N17 C72-N25 O72-N25 Gibson Ave Inlet 18" RCP; 153 ft 167.5 Local 29 10 13 16 22 25 34 D19-N25 C73-N25 O73-N25 Hillside off of Gibson Ave.18" RCP; 198 ft 167.5 Local 25 10 13 16 22 25 34 D20-N25 C74-N25 O74-N25 End of E. Francis St.24" RCP; 198 ft 167.5 Local 31 10 13 16 22 25 34 N25 C63-N25 O63-N25 E. Francis St. & N. Spring St.24" RCP; 176 ft 172.8 Local 23 12 16 20 27 31 38 OFALL-6 --Oklahoma Flats Outfall Outfall 172.8 --12 16 20 27 31 38 N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 35 2.3 3.1 3.8 5 6 8 N18 C38-N18 O38-N18 Cottonwood Ln.18" RCP; 191 ft 2.5 Local 10 1.6 2.2 2.7 3.6 4.1 5 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 11 4.0 5 7 9 10 13 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 25 6 8 9 13 15 18 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 12 6 8 9 13 15 18 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 12 6 8 9 13 15 18 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 13 6 8 9 13 15 18 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 30 6 8 9 13 15 18 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 25 2.1 2.6 3.2 4.6 6 8 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 40 2.0 2.6 3.2 4.6 6 8 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 50 2.0 2.6 3.2 4.6 6 8 N21 C87-N23 O87-N23 Neale Ave & Gibson Ave Confluence 36" RCP; 279 ft 21.8 Local 40 10 13 16 22 25 32 D26-N23 C88-N23 O88-N23 Neale Ave. & King St.36" RCP; 263 ft 24.8 Local 85 11 14 17 24 27 34 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 33 12 15 19 26 30 37 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 19 12 15 19 26 30 37 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 3.6 0.0 0.0 0.0 7 11 18 OFALL-7 --Neale Ave. Outfall Outfall 24.8 --12 15 19 26 30 37 N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 6 1.5 1.9 2.2 3.2 3.7 5 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -23 1.6 1.9 2.3 3.3 3.9 5 OFALL-8 --Smuggler Mine Outfall Outfall 5.6 --2.2 2.8 3.4 4.9 6 8 N22 C75-N22 O75-N22 King St. (Flooding)18" RCP; 52 ft 1.7 Local 10 0.9 1.2 1.4 2.0 2.3 2.8 D25-N22 C86-N22 O86-N22 King St. (Flooding)18" RCP; 231 ft 1.7 Local 18 0.9 1.2 1.4 2.0 2.3 2.8 * Storm system capacity determined using StormCAD. **Assumed pipe sizes. King Street ALT to Neale Ave. Storm System SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Capacity* (cfs) Conduit ID Overflow ID Flow Rates (cfs) Green = Sufficient Capacity Park Circle Tributary to Oklahoma Flats Outfall Design Point Summary Table Neale Ave. and OK Flats Basin 10-year Detention Alternative (With Easements) Oklahoma Flats Outfall Neale Avenue Storm System Smuggler Mine Outfall Page 3 of 11 P161I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year G08 C27-G08 O27-G08 River Bluff Townhome Intake 18" RCP; 245 ft 5.4 -10 2.8 3.7 5 6 7 9 D08-G08 C25-G08 O25-G08 River Bluff Townhomes 6" CPP 5.4 -0.5 2.8 3.7 5 6.1 7.2 8.6 J06-G10 C26-G10 -River Bluff Townhomes Overflow 5.4 -2.8 3.7 5 6 7 9 D10-G10 C31-G10 O31-G10 Red Mtn. Rd. Crossing 12" CMP**5.4 9 2.8 3.7 5 6 7 9 D09-G10 C24-G10 O24-G10 Red Mtn Rd.18" CMP 5.4 8 0.0 0.0 0.0 0.0 0.0 0.1 G13 C58-G13 O58-G13 Lone Pine Rd.18" RCP; 33 ft 2.7 Local 16 0.8 1.0 1.3 1.8 2.2 2.8 G05 C12-G05 O12-G05X Lone Pine Rd.18" RCP; 26 ft 11.5 Local 12 7 10 12 16 18 22 D30-G08 C57-G06 O57-G06 Lone Pine Rd.18" RCP; 66 ft 14.2 Local 15 8 11 13 17 20 24 D24-G06 C51-G06 O51-G06 Lone Pine Rd.18" RCP; 242 ft 14.2 Local 22 8 11 13 17 20 24 D25-G06 C52-G06 O52-G06 Lone Pine Rd.18" RCP; 279 ft 14.2 Local 19 8 11 13 17 20 24 D26-G06 C53-G06 O53-G06 Lone Pine Rd. & Vine St.18" RCP; 328 ft 14.2 Local 15 8 11 13 17 20 24 D27-G06 C54-G06 O54-G06 Lone Pine Rd. & Independence Pl.18" RCP; 141 ft 14.2 Local 14 8 11 13 17 20 24 G06 C16-G06 O16-G06 Lone Pine Rd. & Rd Mtn. Rd.24" CMP 16.6 Local 39 9 12 15 20 23 27 OFALL-1 --Lone Pine Rd. Outfall Outfall 16.6 --9 12 15 20 23 27 G04 C06-G04 O06-G04 Silverlode Dr. (West)12" HDPE 12.6 Local 18 0.2 0.4 0.6 1.3 1.6 3.1 DW01-G04 ORI01-G04 WEIR01-G04 Silverlode Dr. (West)12" CMP/ Dry Well 12.6 Local 2 0.2 0.4 0.6 1.3 1.6 3.0 DW02-G04 OLET-DW02-G04 WEIR02-G04 Silverlode Dr. (West)Dry Well 12.6 Local 0.0 0.2 0.4 0.6 1.3 1.6 3.0 G02 C05-G02 O05-G02 Silverlode Dr. (Center)24" RCP 2.6 Local 32 0.6 0.7 0.9 1.4 1.7 2.2 D05-G02 C04-G02 O04-G02 Silverlode Dr. (Center)24" CMP 2.6 -47 0.6 0.7 0.9 1.4 1.7 2.2 D06-G02 C03-G02 O03-G02 Silverlode Dr. (Center)24" CMP 2.6 -28 0.6 0.7 0.9 1.4 1.7 2.2 G01 C01-G01 O01-G01 Williams Ranch Dr. (East)24" RCP 12.3 Local 33 1.3 1.8 2.5 4.1 5 8 D02-G02 C02-G02 O02-G02 Williams Ranch Dr. (East)24" CMP 12.3 Local 40 1.3 1.8 2.5 4.1 5 8 D03-G02 C07-G02 O07-G02 Upper Gibson Ave Confluence 36" CMP 14.9 -65 1.8 2.5 3.3 6 7 10 DW08-G03 OLET-DW08-G03 WEIR03-G03 1st Dry Well in Series Dry Well 1 14.9 -0.0 2.3 3.0 4.0 6 7 11 DW05-G03 OLET-DW05-G03 WEIR04-G03 2nd Dry Well in Series Dry Well 2 14.9 -0.0 2.3 3.0 4.0 6 7 11 DW06-G03 OLET-DW06-G03 WEIR06-G03 3rd Dry Well in Series Dry Well 3 14.9 -0.0 2.3 3.0 4.0 6 7 11 DW03-G03 OLET-DW03-G03 WEIR07-G03 4th Dry Well in Series Dry Well 4 14.9 -0.0 2.5 3.0 4.0 6 8 11 DW07-G03 OLET-DW07-G03 WEIR08-G03 5th Dry Well in Series Dry Well 5 14.9 -0.0 2.6 3.2 4.0 6 8 11 DW04-G03 OLET-DW04-G03 WEIR09-G03 6th Dry Well in Series Dry Well 6 14.9 -0.0 2.3 3.2 4.0 6 8 11 P01-G03ALT -WEIR01-G03 Underground Seepage Area Seepage Area 14.9 -9 2.3 3.2 4.0 6 8 11 D25-G05 C86-G05 O86-G05 Teal Ct.18" RCP; 134 ft 12.6 Local 4.0 0.2 0.4 0.6 1.3 1.6 3.1 D12-G03 C69-G05 O69-G05 Teal Ct.18" RCP; 276 ft 27.5 Local 7 0.2 0.4 0.6 1.3 1.6 4.4 N02 C21-N02 O21-N02 Drainage collector above Silverlode Dr.36" CMP 59.4 -25 0.0 0.1 0.3 1.0 1.3 9 D01-N02 C22-N12 O22-N12 Silverlode Dr.36" CMP 59.4 Local 105 0.0 0.1 0.3 1.0 1.3 9 J13-N12 C23-N12 Silverlode Dr.36" CMP 59.4 -75 0.0 0.1 0.3 1.0 1.3 9 N07 C24-N12 O24-N12 Silverlode Dr.12" CMP 1.5 Local 12 0.2 0.3 0.4 0.6 0.7 1.0 J20-12 C34-N12 -Free Silver Ct. Roadside Ditch Ditch 60.9 --0.2 0.4 0.6 1.5 2.0 10 J19-N12 C35-N12 -Free Silver Ct. to Brown Ln.Road runoff 60.9 Local -0.2 0.4 0.6 1.5 2.0 10 D32-G05 C68-N12 O68-N12 Brown Ln.18" RCP; 281 ft 88.4 Local 8 0.4 0.7 1.2 2.8 3.5 13 D14-N12 C65-N16 O65-N16 Brown Ln.18" RCP; 99 ft 88.4 Local 8 0.4 0.7 1.2 2.8 3.5 13 D15-N12 C66-N12 O66-N12 Downstream Brown Ln. & Nicholas Ln.18" RCP; 178 ft 88.4 Local 14 0.4 0.7 1.2 2.8 3.5 13 N12 C28-N12 O28-N12 Brown Ln & Park Cir.18" RCP; 29 ft 6.7 Local 13 6 9 11 14 16 18 D2-N12 C67-N12 O67-N12 Brown Ln & Park Cir.18" RCP; 26 ft 95.1 Local 18 6 9 11 13 14 18 D01-N06 C04-N09 O04-N09 Smuggler Mtn. Rd.18" CMP 14.9 Local 19 0.0 0.0 0.1 0.3 0.4 2.5 N09 C06-N09 O06-N09 Smuggler Mtn. Rd.12" CMP 16.8 Local 4.2 0.0 0.0 0.1 0.3 0.4 2.8 J07-N05 C10-N05 -Smuggler Mtn. Rd.Confluence 16.8 Local -0.0 0.0 0.1 0.3 0.4 2.8 N05 C09-N10 O09-N10 Smuggler Mtn. Rd.12" CMP 23.2 Local 7 0.0 0.0 0.2 0.4 0.6 3.8 P02-N01 OLET03-N10 -Mine retention pit Retention 53.8 --0.1 0.2 0.6 1.8 2.2 8 N08 C15-N08 O15-N08 Smuggler Mtn. Rd.18" CMP 1.5 Local 25 0.1 0.1 0.2 0.3 0.4 0.7 J10-N10 C19-N10 -Smuggler Mtn. Rd.Confluence 55.3 Local -0.2 0.2 0.6 1.9 2.5 8 J08-N10 C14-N10 -Smuggler Mtn. Rd.Confluence 78.5 Local -0.2 0.2 0.8 2.4 3.1 12 N11 C77-N04 O77-N04 Silverlode Dr.18" RCP; 185 ft 0.7 Local 21 0.4 0.5 0.7 0.9 1.1 1.2 D22-N04 C78-N04 O78-N04 Silverlode Dr.18" RCP; 116 ft 0.7 Local 24 0.4 0.5 0.7 0.9 1.0 1.2 N04 C79-N10 O79-N10 Silverlode Dr.18" RCP; 206 ft 9.8 Local 28 1.4 1.8 2.3 3.7 5 6 N10 C84-N13 O84-N13 Park Cir.18" RCP; 172 ft 90.0 Local 22 1.8 2.4 3.1 6 7 18 D24-N13 C85-N13 O85-N13 Park Cir.18" RCP; 185 ft 90.0 Local 16 1.8 2.4 3.1 6 7 18 D22-N13 C81-N13 O81-N13 Park Cir. & Nicholas Ln.18" RCP; 226 ft 90.0 Local 15 1.8 2.4 3.1 6 7 18 D23-N13 C82-N13 O82-N13 Park Cir.18" RCP; 215 ft 90.0 Local 14 1.8 2.4 3.1 6 7 17 N13 C91-N13 O91-N13 End of Tributary at Brown Ln.18" RCP; 40 ft 95.7 Local 17 3.3 4.4 6 9 11 21 SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Design Point Summary Table Gibson Avenue Basin and Neale Avenue & OK Flats Combined 10-yr Conveyance Alternative (With Minimal Easements) River Bluff Townhomes Branch Lone Pine Rd. Outfall Brown Ln. Branch Main Gibson Avenue Basin & Neale Avenue & OK Flats Combined Main Stem Capacity* (cfs) Conduit ID Overflow ID Flow Rates Page 4 of 11 P162I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Design Point Summary Table Gibson Avenue Basin and Neale Avenue & OK Flats Combined 10-yr Conveyance Alternative (With Minimal Easements) River Bluff Townhomes Branch Capacity* (cfs) Conduit ID Overflow ID Flow Rates J17-N17 C31-N17 O31-N17 Brown Ln & Park Cir.18" RCP; 170 ft 190.8 Local 22 9 12 15 21 24 37 J18-N17 C68-N17 O68-N17 Park Cir.18" RCP; 240 ft 191.4 Local 20 10 13 16 22 25 38 D16-N17 C69-N17 O69-N17 Park Cir. & Spruce St.18" RCP; 75 ft 191.4 Local 18 10 13 16 21 25 38 D17-N17 C70-N17 O70-N17 South Ave. & Cottonwood Ln.18" RCP; 237 ft 191.4 Local 18 10 13 16 21 25 38 D18-N17 C71-G07 O71-G07 South Ave. & Gibson Ave.18" RCP; 63 ft 191.4 Local 19 10 13 16 21 25 38 N17 C71-N17 O71-N17 Gibson Ave Inlet 18" RCP; 153 ft 3.6 Local 8 1.7 2.2 2.7 3.7 4.4 6 D33-N17 C72-G07 O72-G07 Gibson Ave.18" RCP; 284 ft 195.0 Local 20 11 15 18 25 30 40 D34-G07 C73-G07 O73-G07 Gibson Ave.24" RCP; 121 ft 195.0 Local 29 11 15 18 25 29 40 G07 C19-G09 O19-G09 Gibson Ave.24" RCP; 373 ft 196.5 Local 40 12 15 19 26 31 42 D07-G09 C20-G09 O20-G09 Gibson Ave.24" RCP; 280 ft 196.5 Local 45 12 15 19 26 31 42 G09 C22-G09 O22-G09 Gibson Ave. Curb Inlet 24" RCP; 16 ft 1.5 Local 5 0.6 0.8 1.0 1.3 1.6 2.0 D08-G10 C21-G10 O21-G10 Gibson Ave.24" RCP; 69 ft 198.0 -20 12 16 20 27 32 43 G10 C18-G11 O18-C11 Red Mtn Rd Crossing 24" RCP; 101 ft 198.7 Local 35 13 17 21 28 33 44 OFALL-3 --Gibson Ave. Outfall Outfall 198.7 --13 17 21 28 33 44 G11 C17-G11 O17-G11 Bridge Curb Inlet at N. Mill St.12" CMP 0.7 Local 4 0.3 0.4 0.4 0.6 0.7 0.9 OFALL-4 --N. Mill St. Bridge Outfall (N.)Outfall 0.7 --0.3 0.4 0.4 0.6 0.7 0.9 G12 C23-G12 O23-G12 Bridge Grate Inlet at N. Mill St.12" CMP 0.2 Local 8 0.1 0.1 0.1 0.2 0.2 0.3 OFALL-5 --N. Mill St. Bridge Outfall (S.)Outfall 0.2 --0.1 0.1 0.1 0.2 0.2 0.3 N25 C74-N25 O74-N25 E. Francis St.18" RCP; 198 ft 5.3 Local 13 2.4 3.1 3.8 5 7 9 D21-N25 C63-N25 O63-N25 E. Francis St.18" RCP; 176 ft 5.3 Local 11 2.3 3.1 3.8 5 7 9 OFALL-6 --E. Francis St. Outfall -5.3 Outfall -2.3 3.1 3.8 5 6 9 N15 C37-N19 O37-N19 Oak Ln. & Cottonwood Ln 24" RCP 5.5 Local 43 2.3 3.1 3.8 5 6 8 N18 C38-N18 O38-N18 Cottonwood Ln.12" RCP 2.5 Local 4 1.6 2.2 2.7 3.6 4.1 5 D03-N19 C39-N19 O39-N19 Cottonwood Ln. Confluence 24" CMP 8.0 Local 11 4.0 5 7 9 10 13 N19 C44-N21 O44-N21 Maple Ln. Confluence 24" RCP 10.6 Local 26 6 8 10 13 15 18 D08-N21 C45-N21 O45-N21 Gibson Ave. & Maple Ln.24" RCP 10.6 Local 12 6 8 10 13 15 18 D09-N21 C46-N21 O46-N21 Gibson Ave.24" CMP 10.6 Local 10 6 8 10 13 15 18 D10-N21 C47-N21 O47-N21 Gibson Ave 24" CMP 10.6 Local 10 6 8 10 13 15 18 D11-N21 C48-N21 O48-N21 East of Gibson Ave & Neale Ave.36" CMP 10.6 Local 15 5.8 7.7 9.4 13 15 18 D04-N20 C41-N21 O41-N21 Gibson Ave. & Matchless Dr.24" PVC 6.3 Local 21 2.1 2.6 3.2 5 6 8 D05-N21 C42-N21 O42-N21 Gibson Ave Tributary 24" RCP 6.3 Local 41 2.1 2.6 3.2 5 6 8 D07-N21 C43-N21 O43-N21 Gibson Ave Tributary 24" RCP 6.3 Local 41 2.0 2.6 3.2 5 6 8 N21 C87-N23 O87-N23 Neale Ave & Gibson Ave Confluence 36" RCP; 279 ft 21.8 Local 35 10 13 16 21 25 32 D26-N23 C88-N23 O88-N23 Neale Ave. & King St.36" RCP; 263 ft 23.5 Local 87 11 14 17 23 27 34 N23 C50-N23 O50-N23 Neale Ave & Queen St.36" CMP 24.8 Local 25 12 15 19 25 30 37 D12-N23 C51-N23 O51-N23 Near Neale Ave Bridge; Grate Inlet 36" CMP 24.8 Local 25 12 15 19 25 30 37 D13-N23 C52-N23 O52-N23 Near Neale Ave. Bridge 12" CMP 24.8 Local 3.6 0.0 0.0 0.0 0.0 5 12 OFALL-7 --Neale Ave. Outfall Outfall 24.8 --12 15 19 25 30 37 N22 C75-N22 O75-N22 King St. (Flooding)18" RCP; 52 ft 1.7 Local 5 0.9 1.2 1.4 2.0 2.3 2.8 D25-N22 C86-N22 O86-N22 King St. (Flooding)18" RCP; 231 ft 1.7 Local 12 0.9 1.2 1.4 2.0 2.3 2.8 N14 C58-N14 O58-N14 Park Ave. Crossing 18" CMP**5.0 Local 6 1.5 1.9 2.2 3.2 3.7 5 D06-N26 C59-N26 O59-N26 Improvised CMP to outfall 18" CMP**5.6 -23 1.6 1.9 2.3 3.3 3.9 5 OFALL-8 --Smuggler Mine Outfall Outfall 5.6 --2.2 2.8 3.4 5 6 8 * Storm system capacity determined using StormCAD. **Assumed pipe sizes. N. Mill St. Bridge Oklahoma Flats Outfall Neale Avenue Storm System King Street ALT to Neale Ave. Storm System Smuggler Mine Outfall Page 5 of 11 P163I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 -32 4.2 6 7 10 12 15 OFALL-09 --Gordon Outfall Outfall 1.3 --0.8 1.0 1.2 1.7 2.0 2.4 OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 --0.7 0.9 1.1 1.5 1.8 2.5 R13 C47-R13 -Aesthetic Pond off of Riverside Ditch Overland runoff 9.1 Local -3.3 4.3 5.2 7 9 11.2 P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 9.1 --3.3 4.3 5.2 7 9 11.2 OFALL-07 --Gordon/Callhan 2 Outfall Outfall 9.1 --3.3 4.2 5.2 7 9 11.3 D06-R11 C65-R11 O65-R11 Eastwood Dr.18" RCP; 182 ft.7.7 Local 7 3.6 4.8 6 8 10 12 D07-R11 C66-R11 O66-R11 Eastwood Dr.18" RCP; 127 ft.7.7 Local 7 3.6 4.8 6 8 10 12 D08-R11 C67-R09 O67-R09 Eastwood R.18" RCP; 123 ft.7.7 Local 8 3.6 4.8 6 8 10 12 D09-R09 C68-R09 O68-R09 Eastwood Dr. to Hwy. 82 18" RCP; 145 ft.7.7 Local 8 3.6 4.8 6 8 10 12 D10-R09 C69-R09 O69-R09 Hwy. 82 18" RCP; 68 ft.7.7 Local 10 5.0 6 8 11 13 18 D11-R09 C70-R19 O70-R19 Hwy. 82 & Crystal Lake Rd.18" RCP; 197 ft.7.7 Local 10 5.0 6 8 11 13 18 D16-R17 C76-R14 O76-R14 Hwy. 82 & McSkimming Rd.18" RCP; 68 ft.2.6 Local 11 0.6 0.7 0.9 1 2 2.1 D12-R19 C71-R19 O71-R19 Hwy. 82 & McSkimming Rd.18" RCP; 284 ft.10.3 Local 20 6 7 9 12 15 20 D13-R19 C72-R04 O72-R04 E. Cooper Ave.18" RCP; 307 ft.10.3 Local 23 6 7 9 12 15 20 R04 C77-R04 -Upper Salvation Ditch runoff Road runoff 40.2 --3.0 4.4 6.0 10 13 21 D14-R04 C73-R19 O73-R19 E. Cooper Ave. & Alpine Ct.18" RCP; 165 ft.50.5 Local 27 8 11 14 22 27 39 D15-R19 C74-R19 O74-R19 E. Cooper Ave.18" RCP; 170 ft.50.5 Local 25 8 11 14 22 27 39 R12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -1.4 1.9 2.3 3 4 4.5 R17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.7 0.9 1.1 2 2 2.3 D17-R19 C76-R19 O76-R19 E. Cooper Ave. & Lacet Ln.18" RCP; 57 ft.4.7 Local 11 2.1 2.7 3.2 4 5 6.6 D05-R19 C50-R19 O50-R19 E. Cooper Ave. & Midland Ave.18" RCP; 238 ft.55.2 Local 19 10 14 17 26 32 44 R19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.18" RCP; 218 ft.63.0 Local 22 14 18 22 33 40 55 OFALL-10 --E. Cooper Ave. Outfall Outfall 63.0 --14 18 22 33 40 55 R06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.0 0.0 0.1 0.2 0.3 0.9 D20-R07 C90-R07 O90-R07 Midland Park Pl.18" RCP; 198 ft.5.0 22 0.0 0.0 0.1 0.2 0.3 0.9 D28-R05 C91-R07 O91-R07 Miland Park Pl.18" RCP; 160 ft.5.0 26 0.0 0.0 0.1 0.2 0.3 0.9 D29-R07 C92-R07 O92-R07 Midland Park Pl.18" RCP; 172 ft.5.0 19 0.0 0.0 0.1 0.2 0.3 0.9 R07 C35-R07 O35-R07 Park Ave. & North side of Midland Ave.18" RCP; 48 ft.12.3 Local 12 2.9 3.7 4.5 6 8 10.3 DW01-R07 ORI02-R07 WEIR02-R07 Park Ave. & Midland Ave.18" RCP; 57 ft.12.3 Local 10 2.9 3.7 4.5 6 8 10.3 D30-R05 C93-R05 O93-R05 Park Ave.18" RCP; 150 ft.12.3 Local 18 6 7 9 13 14 14 D31-R05 C94-R05 O94-R05 Park Ave. & Regent St.24" RCP; 64 ft.25.0 Local 21 11 14 17 23 26 27 D32-R05 C95-R05 O95-R05 Park Ave.24" RCP; 114 ft.25.0 Local 26 11 14 17 21 22 27 D22-R10 C81-R10 O81-R10 Park Ave. & E. Hopkins Ave.24" RCP; 140 ft.90.6 Local 57 21 27 32 41 45 55 OFALL-06 --E. Hopkins Ave. Outfall Outfall 90.6 --21 27 32 41 45 55 R02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.0 0.1 0.2 0.6 0.7 2.6 R03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --2.2 2.8 3.4 4.7 6 7 J17-R08 C84-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -2.1 2.8 3.4 4.8 6 8 D25-R08 C85-R08 O85-R08 Ardmore Dr. & Ardmore Ct.18" RCP; 73 ft.24.0 10 2.1 2.7 3.3 4.7 6 8 D24-R08 C86-R05 O86-R05 Ardmore Dr.18" RCP; 89 ft.24.0 17 2.1 2.7 3.3 4.7 6 8 D26-R05 C87-R05 O87-R05 Ardmore Dr.18" RCP; 133 ft.24.0 15 2.1 2.7 3.3 4.7 6 8 D33-R05 C98-R05 O98-R05 Ardmore Dr.18" RCP; 185 ft.24.0 16 2.1 2.7 3.3 4.7 6 8 D34-R05 C99-R05 O99-R05 Smuggler Grove Rd.18" RCP; 242 ft.24.0 12 2.1 2.7 3.3 4.7 6 8 R01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.1 0.2 0.4 1.2 1.6 6 D21-R05 C88-R05 O88-R05 Moscotte Ln./Ardmore Dr.18" RCP; 379 ft.31.6 19 0.1 0.2 0.4 1.2 1.6 6 D27-R05 C89-R05 O89-R05 Midland Ave. Mascotte Ln.18" RCP; 127 ft.31.6 6 0.1 0.2 0.4 1.2 1.6 6 D35-R05 C100-R05 O100-R05 Midland Ave. & Smuggler Grove Rd.18" RCP; 127 ft.55.6 10 2.2 2.8 3.6 6 7 14 R08 C39-R08 -Snyder Park Overland runoff 10.0 --7 9 11 15 17 20 P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --7 9 11 15 17 20 P04-R08N ORI-01-R08 WEIR07-R08 North Snyder Park Pond 18" RCP; 128 ft.10.0 -14 6 8 10 13 16 19 D23-R10 C83-R10 O83-R10 E. Hopkins Ave. & Midland Ave.18" RCP; 258 ft.65.6 Local 19 14 14 14 15 17 25 * Storm system capacity determined using StormCAD. Design Point Summary Table Riverside McSkimming Basin 5-year Conveyance Alternative (With Easements) Contributing Area (ac) Road Classification Capacity *(cfs) Conduit ID E. Hopkins Avenue Outfall South Branch Flow Rates (cfs) Green = Sufficient Capacity E. Cooper Avenue Outfall E. Hopkins Avenue Outfall North Branch Gordon Outfall (R) Gordon/Callahan 1 Outfall Gordon/Callahan 2 Outfall SWMM Element ID Location Existing & Proposed Structures Description Overflow ID Callahan Sub OS Retention Page 6 of 11 P164I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 -32 4.2 6 7 10 12 15 OFALL-09 --Gordon Outfall Outfall 1.3 --0.8 1.0 1.2 1.7 2.0 2.4 OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 --0.7 0.9 1.1 1.5 1.8 2.5 R13 C47-R13 -Aesthetic Pond off of Riverside Ditch Overland runoff 9.1 Local -3.3 4.3 5 7 9 11 P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 9.1 --3.3 4.3 5 7 9 11 OFALL-07 --Gordon/Callhan 2 Outfall Outfall 9.1 --3.3 4.2 5 7 9 11 D06-R11 C65-R11 O65-R11 Eastwood Dr.18" RCP; 182 ft.7.7 Local 7 3.6 5 6 8 10 12 D07-R11 C66-R11 O66-R11 Eastwood Dr.18" RCP; 127 ft.7.7 Local 7 3.6 5 6 8 10 12 D08-R11 C67-R09 O67-R09 Eastwood R.18" RCP; 123 ft.7.7 Local 12 3.6 5 6 8 10 12 D09-R09 C68-R09 O68-R09 Eastwood Dr. to Hwy. 82 18" RCP; 145 ft.7.7 Local 35 3.6 5 6 8 10 12 D10-R09 C69-R09 O69-R09 Hwy. 82 18" RCP; 68 ft.7.7 Local 10 5 6 8 11 13 18 D11-R09 C70-R19 O70-R19 Hwy. 82 & Crystal Lake Rd.18" RCP; 197 ft.7.7 Local 10 5 6 8 11 13 18 D16-R17 C76-R14 O76-R14 Hwy. 82 & McSkimming Rd.18" RCP; 68 ft.2.6 Local 11 0.6 0.7 0.9 1.3 1.6 2.1 D12-R19 C71-R19 O71-R19 Hwy. 82 & McSkimming Rd.18" RCP; 284 ft.10.3 Local 20 6 7 9 12 15 20 D13-R19 C72-R04 O72-R04 E. Cooper Ave.18" RCP; 307 ft.10.3 Local 23 6 7 9 12 15 20 R04 C77-R04 -Upper Salvation Ditch runoff Road runoff 40.2 --3.0 4.4 6 10 13 21 D14-R04 C73-R19 O73-R19 E. Cooper Ave. & Alpine Ct.18" RCP; 165 ft.50.5 Local 27 8 11 14 22 27 39 D15-R19 C74-R19 O74-R19 E. Cooper Ave.18" RCP; 170 ft.50.5 Local 25 8 11 14 22 27 39 R12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -1.4 1.9 2.3 3.1 3.6 4.5 R17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.7 0.9 1.1 1.5 1.8 2.3 D17-R19 C76-R19 O76-R19 E. Cooper Ave. & Lacet Ln.18" RCP; 57 ft.4.7 Local 11 2.1 2.7 3.2 4.4 5 7 D05-R19 C50-R19 O50-R19 E. Cooper Ave. & Midland Ave.18" RCP; 238 ft.55.2 Local 19 10 14 17 26 32 44 R19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.18" RCP; 218 ft.63.0 Local 22 14 18 22 33 40 55 OFALL-10 --E. Cooper Ave. Outfall Outfall 63.0 --14 18 22 33 40 55 R06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.0 0.0 0.1 0.2 0.3 0.9 D20-R07 C90-R07 O90-R07 Midland Park Pl.18" RCP; 198 ft.5.0 23 0.0 0.0 0.1 0.2 0.3 0.9 D28-R05 C91-R07 O91-R07 Miland Park Pl.18" RCP; 160 ft.5.0 26 0.0 0.0 0.1 0.2 0.3 0.9 D29-R07 C77-R07 O77-R07 Midland Park Pl.18" RCP; 105 ft.5.0 15 0.0 0.0 0.1 0.2 0.3 0.9 D36-R07 C78-R07 O78-R07 Park Ave. & North side of Midland Ave.18" RCP; 129 ft.12.3 Local 17 0.0 0.0 0.1 0.2 0.3 0.9 DW01-R07 ORI02-R07 WEIR02-R07 Park Ave. & Midland Ave.18" RCP; 57 ft.12.3 Local 14 0.0 0.0 0.1 0.2 0.3 0.9 D30-R05 C93-R05 O93-R05 Park Ave.18" RCP; 150 ft.12.3 Local 17 0.0 0.0 0.0 0.2 0.3 0.9 D31-R05 C94-R05 O94-R05 Park Ave. & Regent St.24" RCP; 64 ft.25.0 Local 22 5 6 8 11 13 16 D32-R05 C95-R05 O95-R05 Park Ave.24" RCP; 114 ft.25.0 Local 26 5 6 8 11 13 16 D22-R10 C81-R10 O81-R10 Park Ave. & E. Hopkins Ave.24" RCP; 140 ft.90.6 Local 56 15 19 23 30 35 46 OFALL-06 --E. Hopkins Ave. Outfall Outfall 90.6 --15 19 23 30 35 46 R02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.0 0.1 0.2 0.6 0.7 2.6 R03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --2.2 2.8 3.4 5 6 7 J17-R08 C84-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -2.1 2.8 3.4 5 6 8 D25-R08 C85-R08 O85-R08 Ardmore Dr. & Ardmore Ct.18" RCP; 73 ft.24.0 10 2.1 2.7 3.3 5 6 8 D24-R08 C86-R05 O86-R05 Ardmore Dr.18" RCP; 89 ft.24.0 17 2.1 2.7 3.3 5 6 8 D26-R05 C87-R05 O87-R05 Ardmore Dr.18" RCP; 133 ft.24.0 16 2.1 2.7 3.3 5 6 8 D33-R05 C76-R05 O76-R05 Ardmore Dr.18" RCP; 102 ft.24.0 14 2.1 2.7 3.3 5 6 8 R01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.1 0.2 0.4 1.2 1.6 6 D21-R05 C88-R05 O88-R05 Moscotte Ln./Ardmore Dr.18" RCP; 379 ft.55.6 12 2.2 2.8 3.6 6 7 14 D27-R05 C89-R05 O89-R05 Midland Ave. Mascotte Ln.18" RCP; 127 ft.55.6 9 2.2 2.8 3.6 6 7 14 D35-R05 C100-R05 O100-R05 Midland Ave. & Smuggler Grove Rd.18" RCP; 127 ft.55.6 12 2.2 2.8 3.6 6 7 14 R08 C39-R08 -Snyder Park Overland runoff 10.0 --7 9 11 15 17 20 P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --7 9 11 15 17 20 P04-R08N ORI-01-R08 WEIR07-R08 North Snyder Park Pond 18" RCP; 128 ft.10.0 -14 6 8 10 13 16 19 D23-R10 C83-R10 O83-R10 E. Hopkins Ave. & Midland Ave.18" RCP; 258 ft.65.6 Local 18 14 14 14 15 17 25 * Storm system capacity determined using StormCAD. E. Hopkins Avenue Outfall South Branch Flow Rates (cfs) Green = Sufficient Capacity E. Cooper Avenue Outfall E. Hopkins Avenue Outfall North Branch Gordon Outfall (R) Gordon/Callahan 1 Outfall Gordon/Callahan 1 Outfall SWMM Element ID Location Existing & Proposed Structures Description Overflow ID Callahan Sub OS Retention Design Point Summary Table Riverside McSkimming Basin 5-year Conveyance Alternative (With Minimal Easements) Contributing Area (ac) Road Classification Capacity *(cfs) Conduit ID Page 7 of 11 P165I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 -32 4.2 6 7 10 12 15 OFALL-09 --Gordon Outfall Outfall 1.3 --0.8 1.0 1.2 1.7 2.0 2.4 OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 --0.7 0.9 1.1 1.5 1.8 2.5 R13 C47-R13 -Aesthetic Pond off of Riverside Ditch Overland runoff 9.1 Local -3.3 4.3 5 7 9 11.2 P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 9.1 --3.3 4.3 5 7 9 11.2 OFALL-07 --Gordon/Callhan 2 Outfall Outfall 9.1 --3.3 4.2 5 7 9 11.3 D06-R11 C65-R11 O65-R11 Eastwood Dr.18" RCP; 182 ft.7.7 Local 7 3.6 4.8 6 8 10 12 D07-R11 C66-R11 O66-R11 Eastwood Dr.18" RCP; 127 ft.7.7 Local 7 3.6 4.8 6 8 10 12 D08-R11 C67-R09 O67-R09 Eastwood R.18" RCP; 123 ft.7.7 Local 12 3.6 4.8 6 8 10 12 D09-R09 C68-R09 O68-R09 Eastwood Dr. to Hwy. 82 18" RCP; 145 ft.7.7 Local 35 3.6 4.8 6 8 10 12 D10-R09 C69-R09 O69-R09 Hwy. 82 18" RCP; 68 ft.7.7 Local 9 5 6 8 11 13 18 D11-R09 C70-R19 O70-R19 Hwy. 82 & Crystal Lake Rd.18" RCP; 197 ft.7.7 Local 13 5 6 8 11 13 18 D16-R17 C76-R14 O76-R14 Hwy. 82 & McSkimming Rd.18" RCP; 68 ft.2.6 Local 12 0.6 0.7 1 1 2 2 D12-R19 C71-R19 O71-R19 Hwy. 82 & McSkimming Rd.18" RCP; 284 ft.10.3 Local 19 6 7 9 12 15 20 D13-R19 C72-R04 O72-R04 E. Cooper Ave.18" RCP; 307 ft.10.3 Local 23 6 7 9 12 15 20 R04 C77-R04 -Upper Salvation Ditch runoff Road runoff 40.2 --3.0 4.4 6 10 13 21 D14-R04 C73-R19 O73-R19 E. Cooper Ave. & Alpine Ct.18" RCP; 165 ft.50.5 Local 27 8 11 14 22 27 39 D15-R19 C74-R19 O74-R19 E. Cooper Ave.18" RCP; 170 ft.50.5 Local 25 8 11 14 22 27 39 R12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -1.4 1.9 2 3 4 4.5 R17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.7 0.9 1 2 2 2.3 D17-R19 C76-R19 O76-R19 E. Cooper Ave. & Lacet Ln.18" RCP; 57 ft.4.7 Local 11 2.1 2.7 3 4 5 7 D05-R19 C50-R19 O50-R19 E. Cooper Ave. & Midland Ave.18" RCP; 238 ft.55.2 Local 20 10.2 13.6 17 26 32 44 R19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.24" RCP; 218 ft.63.0 Local 44 13.5 17.8 22 33 40 55 OFALL-10 --E. Cooper Ave. Outfall Outfall 63.0 --13.5 17.8 22 33 40 55 R06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.0 0.0 0.1 0.2 0.3 0.9 D20-R07 C90-R07 O90-R07 Midland Park Pl.18" RCP; 198 ft.5.0 22 0.0 0.0 0.1 0.2 0.3 0.9 D28-R05 C91-R07 O91-R07 Miland Park Pl.18" RCP; 160 ft.5.0 26 0.0 0.0 0.1 0.2 0.3 0.9 D29-R07 C92-R07 O92-R07 Midland Park Pl.18" RCP; 172 ft.5.0 19 0.0 0.0 0.1 0.2 0.3 0.9 R07 C35-R07 O35-R07 Park Ave. & North side of Midland Ave.18" RCP; 48 ft.12.3 Local 12 2.9 3.7 5 6 8 10 DW01-R07 ORI02-R07 WEIR02-R07 Park Ave. & Midland Ave.18" RCP; 57 ft.12.3 Local 10 2.9 3.7 5 6 8 10 D30-R05 C93-R05 O93-R05 Park Ave.18" RCP; 150 ft.12.3 Local 18 6 7 9 13 14 14 D31-R05 C94-R05 O94-R05 Park Ave. & Regent St.24" RCP; 64 ft.25.0 Local 21 11 14 17 23 26 27 D32-R05 C95-R05 O95-R05 Park Ave.24" RCP; 114 ft.25.0 Local 26 11 14 17 21 22 27 D22-R10 C81-R10 O81-R10 Park Ave. & E. Hopkins Ave.24" RCP; 140 ft.90.6 Local 57 21 27 32 41 45 55 OFALL-06 --E. Hopkins Ave. Outfall Outfall 90.6 --21 27 32 41 45 55 R02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.0 0.1 0.2 0.6 0.7 2.6 R03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --2.2 2.8 3.4 5 6 7.4 J17-R08 C84-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -2.1 2.8 3.4 5 6 8 D25-R08 C85-R08 O85-R08 Ardmore Dr. & Ardmore Ct.18" RCP; 73 ft.24.0 10 2.1 2.7 3.3 5 6 8 D24-R08 C86-R05 O86-R05 Ardmore Dr.18" RCP; 89 ft.24.0 17 2.1 2.7 3.3 5 6 8 D26-R05 C87-R05 O87-R05 Ardmore Dr.18" RCP; 133 ft.24.0 15 2.1 2.7 3.3 5 6 8 D33-R05 C98-R05 O98-R05 Ardmore Dr.18" RCP; 185 ft.24.0 16 2.1 2.7 3.3 5 6 8 D34-R05 C99-R05 O99-R05 Smuggler Grove Rd.18" RCP; 242 ft.24.0 12 2.1 2.7 3.3 5 6 8 R01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.1 0.2 0.4 1.2 1.6 6 D21-R05 C88-R05 O88-R05 Moscotte Ln./Ardmore Dr.18" RCP; 379 ft.31.6 19 0.1 0.2 0.4 1.2 1.6 6 D27-R05 C89-R05 O89-R05 Midland Ave. Mascotte Ln.18" RCP; 127 ft.31.6 6 0.1 0.2 0.4 1.2 1.6 6 D35-R05 C100-R05 O100-R05 Midland Ave. & Smuggler Grove Rd.18" RCP; 127 ft.55.6 10 2.2 2.8 3.6 6 7 14 R08 C39-R08 -Snyder Park Overland runoff 10.0 --7 9 11 15 17 20 P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --7 9 11 15 17 20 P04-R08N ORI-01-R08 WEIR07-R08 North Snyder Park Pond 18" RCP; 128 ft.10.0 -14 6 8 10 13 16 19 D23-R10 C83-R10 O83-R10 E. Hopkins Ave. & Midland Ave.18" RCP; 258 ft.65.6 Local 19 14 14 14 15 17 25 * Storm system capacity determined using StormCAD. E. Hopkins Avenue Outfall South Branch Flow Rates (cfs) Green = Sufficient Capacity E. Cooper Avenue Outfall E. Hopkins Avenue Outfall North Branch Gordon Outfall (R) Existing & Proposed Structures Gordon/Callahan 2 Outfall SWMM Element ID Location Existing & Proposed Structures Description Overflow ID Callahan Sub OS Retention Design Point Summary Table Riverside McSkimming Basin 10-year Conveyance Alternative (With Easements) Contributing Area (ac) Road Classification Capacity *(cfs) Conduit ID Page 8 of 11 P166I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year P01-R15 WEIR06-P01-R15 -Callahan Sub OS Retention Area Retention 2.6 -32 4.2 6 7 10 12 15 OFALL-09 --Gordon Outfall Outfall 1.3 --0.8 1.0 1.2 1.7 2.0 2.4 OFALL-08 --Gordon/Callahan 1 Outfall Outfall 1.9 --0.7 0.9 1.1 1.5 1.8 2.5 R13 C47-R13 -Aesthetic Pond off of Riverside Ditch Overland runoff 9.1 Local -3.3 4.3 5 7 9 11 P02-R13 WEIR04-P02-R13 -Aesthetic Pond off of Riverside Ditch Aesthetic Pond 9.1 --3.3 4.3 5 7 9 11 OFALL-07 --Gordon/Callhan 2 Outfall Outfall 9.1 --3.3 4.2 5 7 9 11 D06-R11 C65-R11 O65-R11 Eastwood Dr.18" RCP; 182 ft.7.7 Local 7 3.6 5 6 8 10 12 D07-R11 C66-R11 O66-R11 Eastwood Dr.18" RCP; 127 ft.7.7 Local 7 3.6 5 6 8 10 12 D08-R11 C67-R09 O67-R09 Eastwood R.18" RCP; 123 ft.7.7 Local 12 3.6 5 6 8 10 12 D09-R09 C68-R09 O68-R09 Eastwood Dr. to Hwy. 82 18" RCP; 145 ft.7.7 Local 35 3.6 5 6 8 10 12 D10-R09 C69-R09 O69-R09 Hwy. 82 18" RCP; 68 ft.7.7 Local 9 5.0 6 8 11 13 18 D11-R09 C70-R19 O70-R19 Hwy. 82 & Crystal Lake Rd.18" RCP; 197 ft.7.7 Local 13 5.0 6 8 11 13 18 D16-R17 C76-R14 O76-R14 Hwy. 82 & McSkimming Rd.18" RCP; 68 ft.2.6 Local 12 0.6 0.7 0.9 1.3 1.6 2.1 D12-R19 C71-R19 O71-R19 Hwy. 82 & McSkimming Rd.18" RCP; 284 ft.10.3 Local 19 6 7 9 12 15 20 D13-R19 C72-R04 O72-R04 E. Cooper Ave.18" RCP; 307 ft.10.3 Local 23 6 7 9 12 15 20 R04 C77-R04 -Upper Salvation Ditch runoff Road runoff 40.2 --3.0 4.4 6 10 13 21 D14-R04 C73-R19 O73-R19 E. Cooper Ave. & Alpine Ct.18" RCP; 165 ft.50.5 Local 27 8 11 14 22 27 39 D15-R19 C74-R19 O74-R19 E. Cooper Ave.18" RCP; 170 ft.50.5 Local 25 8 11 14 22 27 39 R12 C51-R19 -Riverside Ditch & E. Cooper Ave.Road runoff 2.6 Local -1.4 1.9 2.3 3.1 3.6 4.5 R17 C54-R19 -Riverside Ditch & Lacet Ln Road runoff 2.1 Local -0.7 0.9 1.1 1.5 1.8 2.3 D17-R19 C76-R19 O76-R19 E. Cooper Ave. & Lacet Ln.18" RCP; 57 ft.4.7 Local 11 2.1 2.7 3.2 4.4 5 7 D05-R19 C50-R19 O50-R19 E. Cooper Ave. & Midland Ave.18" RCP; 238 ft.55.2 Local 20 10 14 17 26 32 44 R19 C52-R19 O52-R19 E. Cooper Ave. & S. Riverside Ave.24" RCP; 218 ft.63.0 Local 44 14 18 22 33 40 55 OFALL-10 --E. Cooper Ave. Outfall Outfall 63.0 --13.5 17.8 22 33 40 55 R06 C63-R05 -Smuggler Mtn. Rd.Overland runoff 5.0 --0.0 0.0 0.1 0.2 0.3 0.9 D20-R07 C90-R07 O90-R07 Midland Park Pl.18" RCP; 198 ft.5.0 23 0.0 0.0 0.1 0.2 0.3 0.9 D28-R05 C91-R07 O91-R07 Miland Park Pl.18" RCP; 160 ft.5.0 26 0.0 0.0 0.1 0.2 0.3 0.9 D29-R07 C77-R07 O77-R07 Midland Park Pl.18" RCP; 105 ft.5.0 15 0.0 0.0 0.1 0.2 0.3 0.9 D36-R07 C78-R07 O78-R07 Park Ave. & North side of Midland Ave.18" RCP; 129 ft.12.3 Local 17 0.0 0.0 0.1 0.2 0.3 0.9 DW01-R07 ORI02-R07 WEIR02-R07 Park Ave. & Midland Ave.18" RCP; 57 ft.12.3 Local 14 0.0 0.0 0.1 0.2 0.3 0.9 D30-R05 C93-R05 O93-R05 Park Ave.18" RCP; 150 ft.12.3 Local 17 0.0 0.0 0.0 0.2 0.3 0.9 D31-R05 C94-R05 O94-R05 Park Ave. & Regent St.24" RCP; 64 ft.25.0 Local 22 5 6 8 11 13 16 D32-R05 C95-R05 O95-R05 Park Ave.24" RCP; 114 ft.25.0 Local 26 5 6 8 11 13 16 D22-R10 C81-R10 O81-R10 Park Ave. & E. Hopkins Ave.24" RCP; 140 ft.90.6 Local 56 15 19 23 30 35 46 OFALL-06 --E. Hopkins Ave. Outfall Outfall 90.6 --15 19 23 30 35 46 R02 C21-R01 -Salvation Ditch overflow/Skimming Ln Overland runoff 18.3 --0.0 0.1 0.2 0.6 0.7 2.6 R03 C22-R03 -Salvation Ditch overflow/Skimming Ln Overland runoff 5.7 --2.2 2.8 3.4 5 6 7.4 J17-R08 C84-R08 -Ardmore Ct. & Ardmore Dr.Road runoff 24.0 Local -2.1 2.8 3.4 5 6 8.0 D25-R08 C85-R08 O85-R08 Ardmore Dr. & Ardmore Ct.18" RCP; 73 ft.24.0 10 2.1 2.7 3.3 5 6 8.0 D24-R08 C86-R05 O86-R05 Ardmore Dr.18" RCP; 89 ft.24.0 17 2.1 2.7 3.3 5 6 8.0 D26-R05 C87-R05 O87-R05 Ardmore Dr.18" RCP; 133 ft.24.0 16 2.1 2.7 3.3 5 6 8.0 D33-R05 C76-R05 O76-R05 Ardmore Dr.18" RCP; 102 ft.24.0 14 2.1 2.7 3.3 5 6 8.0 R01 C62-R05 -Entrance to Salvation Ditch piped section Overland runoff 31.6 --0.1 0.2 0.4 1.2 1.6 6.4 D21-R05 C88-R05 O88-R05 Moscotte Ln./Ardmore Dr.18" RCP; 379 ft.55.6 12 2.2 2.8 3.6 6 7 14 D27-R05 C89-R05 O89-R05 Midland Ave. Mascotte Ln.18" RCP; 127 ft.55.6 9 2.2 2.8 3.6 6 7 14 D35-R05 C100-R05 O100-R05 Midland Ave. & Smuggler Grove Rd.18" RCP; 127 ft.55.6 12 2.2 2.8 3.6 6 7 14 R08 C39-R08 -Snyder Park Overland runoff 10.0 --7 9 11 15 17 20 P03-R08S WEIR01-P03-R08S -South Snyder Park Pond Aesthetic Pond 10.0 --7 9 11 15 17 20 P04-R08N ORI-01-R08 WEIR07-R08 North Snyder Park Pond 18" RCP; 128 ft.10.0 -14 6 8 10 13 16 19 D23-R10 C83-R10 O83-R10 E. Hopkins Ave. & Midland Ave.18" RCP; 258 ft.65.6 Local 18 14 14 14 15 17 25 * Storm system capacity determined using StormCAD. E. Hopkins Avenue Outfall South Branch Flow Rates (cfs) Green = Sufficient Capacity E. Cooper Avenue Outfall E. Hopkins Avenue Outfall North Branch Gordon Outfall (R) Gordon/Callahan 1 Outfall Gordon/Callahan 1 Outfall SWMM Element ID Location Existing & Proposed Structures Description Overflow ID Callahan Sub OS Retention Design Point Summary Table Riverside McSkimming Basin 10-year Conveyance Alternative (With Minimal Easements) Contributing Area (ac) Road Classification Capacity *(cfs) Conduit ID Page 9 of 11 P167I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year D13-S03 C37-S01 O37-S01 Upper Mtn. Laurel Dr. low spot 18" RCP; 227 ft 293.5 Local 5 0.3 0.5 0.8 1.5 1.9 4.1 D14-S01 C38-S01 O37-S01 Upper Mtn. Laurel Dr.18" RCP; 189 ft 293.5 Local 9 0.3 0.5 0.8 1.5 1.9 4.1 D08-S02 C32-S02 O32-S02 Upper Mtn. Laurel Dr.18" RCP; 134 ft 478.5 Local 22 0.3 0.6 1.4 4.0 5 36 D20-E03 C52-E03 O52-E03 Upper Mtn. Laurel Dr.18" RCP; 143 ft 478.5 Local 28 0.3 0.6 1.4 4.0 5 36 D06-E03 C21-E04 O21-E04 Upper Mtn. Laurel Dr.18" RCP; 124 ft 490.1 Local 24 0.4 0.7 1.6 5 6 37 D07-E04 C22-E04 O22-E04 Upper Mtn. Laurel Dr.18" RCP; 207 ft 490.1 Local 27 0.4 0.7 1.6 5 6 37 D08-E04 C23-E04 O23-E04 Upper Mtn. Laurel Dr.18" RCP; 134 ft 490.1 Local 25 0.4 0.7 1.6 5 6 37 D09-E04 C24-E02 O24-E02 Upper Mtn. Laurel Dr.18" RCP; 92 ft 490.1 Local 31 0.4 0.7 1.6 5 6 37 D10-E02 C25-E02 O25-E02 Upper Mtn. Laurel Dr.18" RCP; 107 ft 604.1 Local 25 0.4 0.9 2.1 6 8 51 D11-E02 C38-E02 O38-E02 Upper Mtn. Laurel Dr.18" RCP; 233 ft 604.1 Local 27 0.4 0.9 2.1 6 8 51 D20-E02 C39-E02 O39-E02 Upper Mtn. Laurel Dr.18" RCP; 168 ft 604.1 Local 28 0.4 0.9 2.1 6 8 51 D21-E02 C40-E02 O40-E02 Upper Mtn. Laurel Dr.18" RCP; 245 ft 604.1 Local 26 0.4 0.9 2.1 6 8 51 D22-E02 C41-E02 O41-E02 Upper Mtn. Laurel Dr.18" RCP; 47 ft 604.1 Local 23 0.4 0.9 2.1 6 8 51 D11-S02 C31-S08 O31-S08 W. Lupine Dr. & Mtn. Laurel Dr.18" RCP; 261 ft 605.6 Local 25 0.9 1.3 2.5 7 9 52 D12-S08 C44-S08 O44-S08 W. Lupine Dr.18" RCP; 271 ft 605.6 Local 19 0.9 1.3 2.5 7 9 52 D17-S08 C43-S08 O43-S08 W. Lupine Dr.18" RCP; 197 ft 605.6 Local 31 0.9 1.3 2.5 7 9 52 D18-S08 C45-S08 O45-S08 W. Lupine Dr.18" RCP; 169 ft 605.6 Local 26 0.9 1.3 2.5 7 9 52 S08 C46-S09 O46-S09 Lupine Dr. & W. Lupine Dr.18" RCP; 104 ft 611.1 Local 20 3.2 4.1 5 10 13 54 D31-S10 C64-S09 O64-S09 Lupine Dr.18" RCP; 190 ft 611.1 Local 25 3.2 4.1 5 10 13 54 S09 C47-S10 O47-S10 Lupine Dr. & Hwy 82 24" RCP; 226 ft 613.5 Arterial 27 4.1 5 7 11 15 55 D07-S10 C48-S10 O48-S10 Hwy 82 24" RCP; 95 ft 628.8 Arterial 25 12 15 19 27 33 62 D19-S10 C49-S12 O49-S12 Hwy 82 to Sparovic Lot (Private Easement) Outfall 24" RCP; 108 ft 628.8 -33 12 15 19 27 33 62 OFALL-3 --Proposed Central Outfall Outfall 628.8 --12 15 19 27 33 62 D02-S06 C39-S05 O39-S05 Mtn. Laurel Dr. low spot 18" RCP; 397 ft 2.1 Local 9 0.9 1.2 1.5 2.1 2.5 3.2 D01-S05 C40-S04 O40-S04 Mtn. Laurel Dr. low spot 18" RCP; 291 ft 6.4 Local 9 2.6 3.4 4.1 6 7 9 D15-S04 C41-S04 O41-S04 Mtn. Laurel Dr. & Private Dr.18" RCP; 234 ft 6.4 Local 18 2.6 3.4 4.1 6 7 9 D16-S04 C42-S04 O42-S04 Mtn. Laurel Dr.18" RCP; 156 ft 6.4 Local 30 2.6 3.4 4.1 6 7 9 D03-S04 C26-S04 O26-S04 Mountain Valley Easement 18" RCP; 132 ft 11.7 Local 29 5 6 7 10 12 15 D04-S07 C25-S07 O25-S07 Mountain Valley Easement 18" RCP; 106 ft 11.7 -34 5 6 7 10 12 15 D05-S07 C23-S07 O23-S07 E. Lupine Dr.18" RCP; 304 ft 11.7 Local 19 5 6 7 10 12 15 D06-S10 C24-S10 O24-S10 E. Lupine Dr. & Mountain Valley Easement 18" RCP; 206 ft 15.3 Local 27 6 8 10 14 16 21 OFALL-2 -- Private Northern Outfall Outfall 0.8 --0.4 0.5 0.6 0.9 1.0 1.2 OFALL-1 --Private Southern Outfall Outfall 2.0 --0.0 0.1 0.1 0.3 0.5 1.0 D12-E02 C33-E02 O33-E02 Northway Dr.18" RCP; 182 ft 24.9 Local 22 10 13 16 22 26 35 D15-E02 C32-E02 O32-E02 Northway Dr.18" RCP; 165 ft 24.9 Local 31 10 13 16 22 26 35 D16-E02 C28-E02 O28-E02 Northway Dr. & Roaring Fork Dr.18" RCP; 176 ft 24.9 Local 25 10 13 16 22 26 35 D17-E02 C29-E02 O29-E02 Roaring Fork Dr.18" RCP; 130 ft 24.9 Local 28 10 13 16 22 26 35 D14-E02 C31-E02 O31-E02 Roaring Fork Dr.18" RCP; 264 ft 24.9 Local 25 10 13 16 22 26 35 D18-E02 C30-E02 O30-E02 Hwy 82 & Roaring Fork Dr.24" RCP; 171 ft 24.9 Arterial 16 10 13 16 22 26 35 D19-E02 C35-E02 O35-E02 Hwy 82 crossing 24" RCP; 202 ft 24.9 Arterial 16 10 13 16 22 26 35 D32-E06 C69-E06 O69-E06 Hwy 82 & Stillwater Dr.24" RCP; 202 ft 24.9 Arterial 22 10 13 16 22 26 34 D34-E06 C70-E06 O70-E06 Stillwater Dr.24" RCP; 150 ft 24.9 Arterial 33 10 13 16 22 26 34 D33-E06 C71-E06 O71-E06 Stillwater Dr.24" RCP; 30 ft 24.9 Local 22 10 13 16 22 26 34 OFALL-01 --Stillwater Dr. Bridge Outfall Outfall 24.9 --10 13 16 22 26 34 E05 C34-E05 O34-E05 Hwy 82 crossing 18" CMP 2.6 Arterial 5 1.4 1.8 2.2 3.0 3.6 4.3 OFALL-02 --Stillwater Ranch Outfall Outfall 6.2 --1.4 1.8 2.2 3.0 3.6 4.3 *Capacities estimated separately in StormCAD. Eastwood Basin North System Stillwater Bridge Basin Main Stem Stillwater Bridge Basin South Branch Private Outfall Eastwood Basin Main System Design Point Summary Table Stillwater Bridge Basin & Eastwood Basin 10-year Conveyance Alternative (With Easements) Flow Rates (cfs) Green = Sufficient Capacity SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Capacity (cfs) * Conduit ID Overflow ID Page 10 of 11 P168I. Table 5.3 Alternatives Summary Table 2-year 5-year 10-year 25-year 50-year 100-year D13-S03 C37-S01 O37-S01 Upper Mtn. Laurel Dr. low spot 18" RCP; 227 ft 293.5 Local 5 0.3 0.5 0.8 1.5 1.9 4.1 D14-S01 C38-S01 O37-S01 Upper Mtn. Laurel Dr.18" RCP; 189 ft 293.5 Local 9 0.3 0.5 0.8 1.5 1.9 4.1 D08-S02 C32-S02 O32-S02 Upper Mtn. Laurel Dr.18" RCP; 134 ft 478.5 Local 22 0.3 0.6 1.4 4.0 5 36 D20-E03 C52-E03 O52-E03 Upper Mtn. Laurel Dr.18" RCP; 143 ft 478.5 Local 28 0.3 0.6 1.4 4.0 5 36 D06-E03 C21-E04 O21-E04 Upper Mtn. Laurel Dr.18" RCP; 124 ft 490.1 Local 24 0.4 0.7 1.6 4.5 6 37 D07-E04 C22-E04 O22-E04 Upper Mtn. Laurel Dr.18" RCP; 207 ft 490.1 Local 27 0.4 0.7 1.6 4.5 6 37 D08-E04 C23-E04 O23-E04 Upper Mtn. Laurel Dr.18" RCP; 134 ft 490.1 Local 25 0.4 0.7 1.6 4.5 6 37 D09-E04 C24-E02 O24-E02 Upper Mtn. Laurel Dr.18" RCP; 92 ft 490.1 Local 31 0.4 0.7 1.6 4.5 6 37 D10-E02 C25-E02 O25-E02 Upper Mtn. Laurel Dr.18" RCP; 107 ft 604.1 Local 25 0.4 0.9 2.1 6 8 51 D11-E02 C38-E02 O38-E02 Upper Mtn. Laurel Dr.18" RCP; 233 ft 604.1 Local 27 0.4 0.9 2.1 6 8 51 D20-E02 C39-E02 O39-E02 Upper Mtn. Laurel Dr.18" RCP; 168 ft 604.1 Local 28 0.4 0.9 2.1 6 8 51 D21-E02 C40-E02 O40-E02 Upper Mtn. Laurel Dr.18" RCP; 245 ft 604.1 Local 26 0.4 0.9 2.1 6 8 51 D22-E02 C41-E02 O41-E02 Upper Mtn. Laurel Dr.18" RCP; 47 ft 604.1 Local 23 0.4 0.9 2.1 6 8 51 D11-S02 C31-S08 O31-S08 W. Lupine Dr. & Mtn. Laurel Dr.18" RCP; 261 ft 605.6 Local 25 0.9 1.3 2.5 7 9 52 D12-S08 C44-S08 O44-S08 W. Lupine Dr.18" RCP; 271 ft 605.6 Local 19 0.9 1.3 2.5 7 9 52 D17-S08 C43-S08 O43-S08 W. Lupine Dr.18" RCP; 197 ft 605.6 Local 31 0.9 1.3 2.5 7 9 52 D18-S08 C45-S08 O45-S08 W. Lupine Dr.18" RCP; 169 ft 605.6 Local 27 0.9 1.3 2.5 7 9 52 S08 C46-S09 O46-S09 Lupine Dr. & W. Lupine Dr.18" RCP; 104 ft 611.1 Local 27 3.2 4.1 5.4 10 13 54 D31-S10 C64-S09 O64-S09 Lupine Dr.18" RCP; 190 ft 626.4 Local 21 9 12 15 23 28 60 S09 C72-S09 O72-S09 Lupine Dr. & Hwy 82 30" RCP; 161 ft 616.5 Arterial 28 11 15 18 27 32 62 D07-S10 C47-S10 O47-S10 Hwy 82 18" RCP; 226 ft 3.0 Arterial 4 1.8 2.4 2.8 3.9 4.7 6 D32-E06 C69-E06 O69-E06 Hwy 82 & Stillwater Dr.30" RCP; 202 ft 641.4 Arterial 34 21 27 34 48 58 88 D34-E06 C70-E06 O70-E06 Stillwater Dr.30" RCP; 150 ft 641.4 Arterial 40 21 27 34 48 58 88 D33-E06 C71-E06 O71-E06 Stillwater Dr.30" RCP; 30 ft 641.4 Local 40 21 27 34 48 58 88 OFALL-01 --Stillwater Dr. Bridge Outfall Outfall 641.4 --21 27 34 48 58 88 D02-S06 C39-S05 O39-S05 Mtn. Laurel Dr. low spot 18" RCP; 397 ft 2.1 Local 10 0.9 1.2 1.5 2.1 2.5 3.2 D01-S05 C40-S04 O40-S04 Mtn. Laurel Dr. low spot 18" RCP; 291 ft 6.4 Local 8 2.6 3.4 4.1 6 7 9 D15-S04 C41-S04 O41-S04 Mtn. Laurel Dr. & Private Dr.18" RCP; 234 ft 6.4 Local 30 2.6 3.4 4.1 6 7 9 D16-S04 C42-S04 O42-S04 Mtn. Laurel Dr.18" RCP; 156 ft 6.4 Local 30 2.6 3.4 4.1 6 7 9 D03-S04 C53-S04 O53-S04 Mtn. Laurel Dr.18" RCP; 87 ft 11.7 Local 22 4.5 6 7 10 12 15 D21-S04 C54-S04 O54-S04 Mtn. Laurel Dr.18" RCP; 120 ft 11.7 Local 23 4.5 6 7 10 12 15 D22-S04 C55-S04 O55-S04 Mtn. Laurel Dr.18" RCP; 92 ft 11.7 Local 10 4.5 6 7 10 12 15 D23-S04 C56-S04 O56-S04 Mtn. Laurel Dr.18" RCP; 259 ft 11.7 Local 19 4.5 6 7 10 12 15 D24-S04 C57-S04 O57-S04 E. Lupine Dr.18" RCP; 256 ft 11.7 Local 13 4.5 6 7 10 12 15 D25-S04 C58-S04 O58-S04 E. Lupine Dr.18" RCP; 302 ft 11.7 Local 20 4.5 6 7 10 12 15 D05-S07 C23-S07 O23-S07 E. Lupine Dr.18" RCP; 304 ft 11.7 Local 23 4.5 6 7 10 12 15 D06-S10 C65-S07 O65-S07 E. Lupine Dr.18" RCP; 176 ft 15.3 Local 10 6 8 10 13 16 20 D30-S10 C67-S10 O67-S10 E. Lupine Dr.18" RCP; 159 ft 15.3 Local 10 6 8 10 13 16 20 OFALL-2 -- Private Northern Outfall Outfall 0.8 --0.4 0.5 0.6 0.9 1.0 1.2 OFALL-1 --Private Southern Outfall Outfall 2.0 --0.0 0.1 0.1 0.3 0.5 1.0 D12-E02 C33-E02 O33-E02 Northway Dr.18" RCP; 182 ft 24.9 Local 22 10 13 16 22 26 35 D15-E02 C32-E02 O32-E02 Northway Dr.18" RCP; 165 ft 24.9 Local 31 10 13 16 22 26 35 D16-E02 C28-E02 O28-E02 Northway Dr. & Roaring Fork Dr.18" RCP; 176 ft 24.9 Local 25 10 13 16 22 26 35 D17-E02 C29-E02 O29-E02 Roaring Fork Dr.18" RCP; 130 ft 24.9 Local 30 10 13 16 22 26 35 D14-E02 C31-E02 O31-E02 Roaring Fork Dr.18" RCP; 264 ft 24.9 Local 34 10 13 16 22 26 35 D18-E02 C30-E02 O30-E02 Hwy 82 & Roaring Fork Dr.24" RCP; 171 ft 24.9 Arterial 22 10 13 16 22 26 35 D19-E02 C35-E02 O35-E02 Hwy 82 crossing 24" RCP; 202 ft 24.9 Arterial 23 10 13 16 22 26 34 E05 C34-E05 O34-E05 Hwy 82 crossing 18" CMP 2.6 Arterial 5 1.4 1.8 2.2 3.0 3.6 4.3 OFALL-02 --Stillwater Ranch Outfall Outfall 6.2 --1.3 1.8 2.1 3.0 3.5 4.3 *Capacities estimated separately in StormCAD. Eastwood Basin North System Stillwater Bridge Basin Main Stem Stillwater Bridge Basin South Branch Private Outfall Eastwood Basin Main System Design Point Summary Table Stillwater Bridge Basin & Eastwood Basin 10-year Conveyance Alternative (Without Easements) Flow Rates (cfs) Green = Sufficient Capacity SWMM Element ID Location Existing & Proposed Structures Description Contributing Area (ac) Road Classification Capacity (cfs) * Conduit ID Overflow ID Page 11 of 11 P169I. P170I. 5-28 | Alternative Development April 2015 5.5 ALTERNATIVE COST ESTIMATES The capital costs of detention and structure improvements, conveyance improvements, and local structure improvements alternatives were estimated by assembling necessary design requirements using the previously discussed criteria, and estimating the unit costs of each component in a set of improvements. Unit costs for each proposed item for each alternative were calculated based on the 2011, 2012, and 2013 Colorado Department of Transportation (CDOT) cost data as well as recorded costs from Ute Avenue work in Aspen in 2013 and the UD-MP Cost software from UDFCD (Version 2.2). Available values for each cost item were averaged and a 20% location adjustment was added to account for inflation and uncertainty of costs for obtaining and transporting materials to Aspen. These unit costs are presented in the “Unit Cost Database” spreadsheet in Appendix F. Land acquisition costs were included for the detention facilities in the alternatives analysis, and for other improvements on private land. Land easement costs are listed in the cost estimation calculation packet in Appendix F. Culvert costs are based on a per linear foot of pipe with flared end sections or two wing walls as appropriate, complete-in-place, with the estimated number of manholes needed for the system. The cost of detention ponds is based on the cubic yards of excavation and embankment, an estimated cost for an outlet structure, and the cost of the land required for the facility. Design engineering costs are added to the total cost of each alternative as 20 percent of the construction costs. Construction contingencies (30 percent) are also added to the total construction cost of each alternative to account for such items as utility relocations, mobilization, temporary erosion control, and construction engineering. Operations and maintenance costs have not been specifically estimated for the improvements; however, given the nature of the proposed improvements, maintenance should be limited to periodic inspection and sediment removal. Permitting costs have also not been specifically estimates for the improvements, as the permits may vary based on final configuration of a given project. The total estimated capital costs for each alternative are based on the sum of the cost of the proposed facilities, plus costs for engineering and construction contingencies. Detailed cost estimates for each alternative for each basin are included in Table 5.4. P171 I. April 2015 5-29 | Alternative Development This page intentionally left blank P172 I. Table 5.4 Alternative Cost Estimates Projects Location Size Construction Cost Construction Contingency (30%) Subtotal Construction Cost Design Contingency (20%) Land Cost Total Cost (x$1,000) 1. Williams Woods Proposed System ft 1-18" RCP H-05 to J02-H03 784 86,450$25,935$112,385$17,290$-$130$ 18" RCP Easement D12-H03 to J02-H03 68 -$-$-$-$53,857$54$ 18" FES J02-H03 -1,189$357$1,546$238$-$2$ yd3 Proposed system outfall riprap protection J02-H03 3 459$138$597$92$-$1$ Total Cost 88,098$26,429$114,527$17,620$53,857$186$ 10-year Conveyance Alternative Hunter Creek Basin Page 1 of 4 P173 I. Table 5.4 Alternative Cost Estimates Projects Location Size Construction Cost Construction Contingency (30%) Subtotal Construction Cost Design Contingency (20%) Land Cost Total Cost (x$1,000) 1. River Bluff Townhomes Branch ft 1-18" RCP with FES and Pipe headwalls/wingwalls G08 to D27-G06 354 39,358$11,807$51,165$7,872$-$59$ Subtotal 59$ 2. Lone Pine Rd. Outfall ft 1-24" RCP with FES D03-G02 to Proposed Detention 118 16,148$4,844$20,992$3,230$-$24$ 1-18" RCP with FES G04 to Proposed Detention 320 41,237$12,371$53,608$8,247$-$62$ 1-18" RCP D12-G03 to D27-G06 2,653 248,631$74,589$323,220$49,726$-$373$ 18" RCP Easements D12-G03 to D32-G05 175 -$-$-$-$174,759$175$ 1-24" RCP D27-G06 to G06 141 16,886$5,066$21,951$3,377$-$25$ 18" RCP Easements D11-G04 to D15-G05 598 -$-$-$-$551,928$552$ 18" RCP Easements D03-G02 to Proposed Detention 118 -$-$-$-$81,267$81$ 18" RCP Easements D18-G05 to D20-G13 243 -$-$-$-$30,303$30$ 18" RCP Easements G08 to D27-G06 305 -$-$-$-$139,463$139$ Subtotal 1,462$ 3. Proposed Detention ft2 Detention Area Easement Proposed Detention (P01-G03ALT)440 -$-$-$-$30,303$30$ Proposed Detention Proposed Detention (P01-G03ALT)0.47 ac-ft 48,915$14,675$63,590$9,783$-$73$ Subtotal 104$ Total Cost 411,174$123,352$534,527$82,235$1,008,023$1,625$ 1. Park Circle Tributary to Oklahoma Flats Outfall ft 1-18" RCP with FES and Pipe headwalls/wingwalls N11 to Proposed Detention 677 70,426$21,128$91,554$14,085$-$106$ 18" RCP Easements N10 to D22-N13 240 -$-$-$-$309,917$310$ 1-18" RCP D22-N13 to J17-N17 481 46,365$13,910$60,275$9,273$-$70$ Subtotal 485$ 2. Oklahoma Flats Outfall ft 1-18" RCP D15-N12 to J17-N17 233 29,561$8,868$38,430$5,912$-$44$ 1-18" RCP J17-N17 to D20-N25 1,162 110,874$33,262$144,136$22,175$-$166$ 18" RCP Easements N17 to D20-N25 313 -$-$-$-$404,184$404$ 1-24" RCP with FES D20-N25 to OFALL-6 374 43,061$12,918$55,980$8,612$-$65$ ft Subtotal 679$ 3. Neale Avenue Storm System 1-36" RCP N21 to N23 542 81,832$24,550$106,382$16,366$-$123$ Subtotal 123$ 4. Smuggler Mine Outfall ft 1-18" RCP N22 to D26-N23 283 28,358$8,507$36,865$5,672$-$43$ Subtotal 43$ 5. Proposed Detention ft2 Detention Area Easement Proposed Detention (P04-N15ALT)780 -$-$-$-$80,579$81$ Proposed Detention Proposed Detention (P04-N15ALT)0.55 ac-ft 49,694$14,908$64,603$9,939$-$75$ Subtotal 155$ Total Cost 460,172$138,052$598,224$92,034$794,680$1,485$ 1. River Bluff Townhomes Branch ft 1-18" RCP with FES and Pipe headwalls/wingwalls G08 to D08-G08 245 22,790$6,837$29,627$4,558$-$34$ 18" RCP Easements G08 to D08-G08 245 -$-$-$-$112,489$112$ Subtotal 147$ 2. Lone Pine Rd. Outfall ft 1-18" RCP with pipe headwall/wingwalls G13 & G05 to G06 1115 112,689 33,807$146,496$22,538$-$169$ Subtotal 169$ 3. Brown Ln. Branch & N12 Branch 1-18" RCP D25-G05 to D2-N12 1023 101,455 30,437$131,892$20,291$-$152$ 18" RCP Easements D25-G05 to D32-G05 270 -$-$-$-$381,198$381$ Subtotal 533$ 4. Main Gibson Ave. Main Stem, N17 Branch, & G09 Branch 1-18" RCP N11 to D34-G07 2567 242,804$72,841$315,645$48,561$-$364$ 1-24" RCP with FES D34-G07 to OFALL-3 960 117,114$35,134$152,248$23,423$-$176$ Subtotal 540$ 5. Oklahoma Flats Outfall 1-18" RCP with FES N25 to OFALL-6 374 35,713$10,714$46,427$7,143$-$54$ Subtotal 54$ 6. Neale Avenue Storm System 1-36" RCP N21 to N23 542 81,832$24,550$106,382$16,366$-$123$ Subtotal 123$ 7. King Street Branch 1-18" RCP N22 to D26-N23 283 28,358$8,507$36,865$5,672$-$43$ Subtotal 43$ Total Cost 742,755$222,826$965,581$148,551$493,687$1,608$ 10-year Gibson Avenue Basin Detention Alternative (With Easements) Combined Gibson Avenue Basin and Neale Avenue & OK Flats Basin 10-year Neale Avenue & OK Flats Basin Detention Alternative (With Easements) 10-year Combined Gibson Avenue Basin and Neale Avenue & OK Flats Basin Conveyance Alternative (With Limited Easements) Page 2 of 4 P174 I. Table 5.4 Alternative Cost Estimates Projects Location Size Construction Cost Construction Contingency (30%) Subtotal Construction Cost Design Contingency (20%) Land Cost Total Cost (x$1,000) 1. E. Cooper Avenue Outfall, Midland and Cooper Branch, & McSkimming Branch ft 1-18" RCP with FES D06-R11 TO OFALL-10 2224 206,978$62,093$269,071$41,396$-$310$ 1-18" RCP Jacked D16-R17 to D12-R19 68 28,391$8,517$36,909$5,678$-$43$ 1-18" RCP Jacked D17-R19 to D05-R19 57 24,541$7,362$31,904$4,908$-$37$ 18" RCP Easement D08-R11 to D10-R09 205 -$-$-$-$149,793$150$ Subtotal 540$ 2. E. Hopkins Outfall North Branch ft 1-18" RCP D20-R07 to D31-R05 785 80,738$24,221$104,959$16,148$-$121$ 1-24" RCP with FES D31-R05 to OFALL-6 318 42,770$12,831$55,600$8,554$-$64$ Subtotal 185$ 3. E. Hopkins Outfall South Branch ft 1-18" RCP D25-R08 to D35-R05 722 71,878$21,563$93,441$14,376$-$108$ 18" RCP Easement D33-R05 to D34-R05 80 -$-$-$60,606$61$ 1-18" RCP D21-R05 to D22-R10 1019 87,410$26,223$113,634$17,482$-$131$ Subtotal 300$ Total Cost 542,705$162,812$705,517$108,541$210,399$1,024$ 1. E. Cooper Avenue Outfall, Midland and Cooper Branch, & McSkimming Branch ft 1-18" RCP with FES D06-R11 TO OFALL-10 2224 206,978$62,093$269,071$41,396$-$310$ 1-18" RCP Jacked D16-R17 to D12-R19 68 28,391$8,517$36,909$5,678$-$43$ 1-18" RCP Jacked D17-R19 to D05-R19 57 24,541$7,362$31,904$4,908$-$37$ 18" RCP Easement D08-R11 to D10-R09 205 -$-$-$-$149,793$150$ Subtotal 540$ 2. E. Hopkins Outfall North Branch ft 1-18" RCP D20-R07 to D31-R05 799 81,686$24,506$106,192$16,337$-$123$ 1-24" RCP with FES D31-R05 to OFALL-6 318 42,770$12,831$55,600$8,554$-$64$ Subtotal 187$ 3. E. Hopkins Outfall South Branch ft 1-18" RCP D25-R08 to D22-R10 1416 132,675$39,803$172,478$26,535$-$199$ Subtotal 199$ Total Cost 517,041$155,112$672,154$103,408$149,793$925$ 1. E. Cooper Avenue Outfall, Midland and Cooper Branch, & McSkimming Branch ft 1-18" RCP D06-R11 to R19 2006 186,426$55,928$242,354$37,285$-$280$ 1-24" RCP with FES R19 to OFALL-10 218 24,868$7,460$32,328$4,974$-$37$ 1-18" RCP Jacked D16-R17 to D12-R19 68 28,391$8,517$36,909$5,678$-$43$ 1-18" RCP Jacked D17-R19 to D05-R19 57 24,541$7,362$31,904$4,908$-$37$ 18" RCP Easement D08-R11 to D10-R09 205 -$-$-$-$149,793$150$ Subtotal 546$ 2. E. Hopkins Outfall North Branch ft 1-18" RCP D20-R07 to D31-R05 785 80,738$24,221$104,959$16,148$-$121$ 1-24" RCP with FES D31-R05 to OFALL-6 318 42,770$12,831$55,600$8,554$-$64$ Subtotal 185$ 3. E. Hopkins Outfall South Branch ft 1-18" RCP D25-R08 to D35-R05 722 71,878$21,563$93,441$14,376$-$108$ 18" RCP Easement D33-R05 to D34-R05 80 -$-$-$-$60,606$61$ 1-18" RCP D21-R05 to D22-R10 1019 88,599$26,580$115,179$17,720$-$133$ Subtotal 301$ Total Cost 548,211$164,463$712,674$109,642$210,399$1,033$ 1. E. Cooper Avenue Outfall, Midland and Cooper Branch, & McSkimming Branch ft 1-18" RCP D06-R11 to R19 2006 186,426$55,928$242,354$37,285$-$280$ 1-24" RCP with FES R19 to OFALL-10 218 24,868$7,460$32,328$4,974$-$37$ 1-18" RCP Jacked D16-R17 to D12-R19 68 28,391$8,517$36,909$5,678$-$43$ 1-18" RCP Jacked D17-R19 to D05-R19 57 24,541$7,362$31,904$4,908$-$37$ 18" RCP Easement D08-R11 to D10-R09 205 -$-$-$-$149,793$150$ Subtotal 546$ 2. E. Hopkins Outfall North Branch ft 1-18" RCP D20-R07 to D31-R05 799 81,686$24,506$106,192$16,337$-$123$ 1-24" RCP with FES D31-R05 to OFALL-6 318 42,770$12,831$55,600$8,554$-$64$ Subtotal 187$ 3. E. Hopkins Outfall South Branch ft 1-18" RCP D25-R08 to D22-R10 1416 132,675$39,803$172,478$26,535$-$199$ Subtotal 199$ Total Cost 521,358$156,407$677,765$104,272$149,793$932$ Riverside McSkimming Basin 10-year Conveyance Alternative (With Easements) 10-year Conveyance Alternative (With Limited Easements) 5-year Conveyance Alternative (With Easements) 5-year Conveyance Alternative (With Limited Easements) Page 3 of 4 P175 I. Table 5.4 Alternative Cost Estimates Projects Location Size Construction Cost Construction Contingency (30%) Subtotal Construction Cost Design Contingency (20%) Land Cost Total Cost (x$1,000) 1. Stillwater Bridge Basin Main Stem ft 1-18" RCP D13-S03 to S09 3,242 306,905$92,072$398,977$61,381$-$460$ 1-24" RCP S09 to OFALL-3 334 44,165$13,249$57,414$8,833$-$66$ Jacked 1-24" RCP D07-S10 95 33,250$9,975$43,225$6,650$-$50$ Subtotal 576$ 2. Stillwater Bridge Basin South Branch ft 1-18" RCP D02-S06 to D07-S10 1,826 160,456$48,137$208,593$32,091$-$241$ 18" RCP Easements D03-S04 to D05-S07 238 -$-$-$-$142,654$143$ 18" RCP Easements D06-S10 206 -$-$-$-$148,301$148$ Subtotal 532$ 3. Eastwood Main System ft 1-18" RCP D12-E02 to D14-E02 917 80,499$24,150$104,649$16,100$-$121$ Jacked 1-24" RCP D18-E02 171 59,850$17,955$77,805$11,970$-$90$ 1-24" RCP D14-E02 to OFALL-01 584 79,737$23,921$103,658$15,947$-$120$ Subtotal 330$ Total Cost 764,862$229,459$994,321$152,972$290,955$1,438$ 1. Stillwater Bridge Basin Main Stem ft 1-18" RCP D13-S03 to S09 3,468 306,905$92,072$398,977$61,381$-$460$ 1-30" RCP S09 to OFALL-01 382 44,165$13,249$57,414$8,833$-$66$ Jacked 1-30" RCP S09 161 33,250$9,975$43,225$6,650$-$50$ Subtotal 576$ 2. Stillwater Bridge Basin South Branch ft 1-18" RCP D02-S06 to D31-S10 2,833 251,645$75,493$327,138$50,329$-$377$ Subtotal 377$ 3. Eastwood Main System ft 1-18" RCP D12-E02 to D14-E02 917 80,499$24,150$104,649$16,100$-$121$ Jacked 1-24" RCP D18-E02 171 59,850$17,955$77,805$11,970$-$90$ 1-24" RCP D14-E02 to D32-E06 202 31,387$9,416$40,803$6,277$-$47$ Subtotal 258$ Total Cost 807,701$242,310$1,050,011$161,540$-$1,212$ 10-year Conveyance Alternative (With Easements) Combined Stillwater Bridge Basin & Eastwood Basin 10-year Conveyance Alternative (Without Eastments) Page 4 of 4 P176 I. April 2015 5-33 | Alternative Development 5.6 DISCUSSION AND RECOMMENDATIONS Based on the evaluation of project benefits, and cost effectiveness, the preferred alternatives suggested for implementation are projects listed in Table 5.5. These chosen alternatives were primarily based on the least amount of cost compared to the other alternatives for each basin. The 10-year conveyance alternative with limited easements in Riverside McSkimming was chosen over the 5-year conveyance alternative with limited easements because of the small cost upgrade to achieve a 10-year system over a 5-year capacity system. All basins have conveyance improvements proposed. The proposed detention alternatives provided little attenuation of peak flows in the upper reaches of each basin to affect flows downstream and proved to be extremely expensive. The locations of these chosen improvements are shown on Figures 5.1 through 5.4. Table 5.5 Proposed Project Costs by Watershed (2013 Dollars) Proposed Projects by Major Basin Land Cost (x$1,000) Construction Cost (x$1,000) Total Cost (x$1,000) Hunter Creek Basin (10-year Conveyance) $54 $132 $186 Combined Gibson Avenue and Neale Avenue & OK Flats Basins (10-year Conveyance) $494 $1,114 $1,608 Riverside McSkimming Basin (10-year Conveyance with Limited Easements) $150 $782 $932 Combined Eastwood and Stillwater Bridge Basins (10-year Conveyance with No Easements) $0 $1,212 $1,212 Total Cost of Proposed Projects $698 $3,240 $3,938 P177 I. 5-34 | Alternative Development April 2015 This page intentionally left blank P178 I. SECTION SIX CONCEPTUAL DESIGN April 2015 6-1 | Conceptual Design 6 Conceptual Design 6.1 CONCEPTUAL DESIGN OVERVIEW Based on the evaluation of the proposed improvement benefits and cost effectiveness, the preferred alternatives for each major basin have been selected, as discussed in Section 5.6 and summarized in Table 5.5. These projects were designed conceptually to confirm performance and probable construction cost. Generally, the overall objectives of implementing drainage and flood control alternatives in Aspen are to: 1. Remove buildings from the 100-year floodplain and reduce flooding. 2. Improve public safety. 3. Improve stormwater quality. 4. Limit costs by reducing land acquisition needed for easements. 5. Leverage cost sharing opportunities. The elements of the conceptual design of the selected projects are summarized in this section. Each selected alternative is described in detail in Section 6.6 with conceptual drawings presented in Appendix G. Per direction from Aspen, only those improvements within the City’s jurisdiction are included in the final Proposed Improvements Plan shown on the conceptual drawings. 6.2 GENERAL RECOMMENDATIONS As part of master planning for urbanizing watersheds, it is generally recommended that Aspen implement the following: • Continue implementing water quality treatment as much as practicable throughout Aspen in accordance with the standards in Chapter 8 of the URMP. • Coordinate with Pitkin County and the Smuggler Mine to ensure that Smuggler Mountain Road is maintained with positive drainage to the existing cross culverts. • Many basins in this Master Plan have significant area within Pitkin County’s jurisdiction. Alternatives were proposed for those areas, but were not included in the conceptual design, per Aspen’s direction. Coordinate future improvement projects with Pitkin County to leverage funding and increase functionality by including the upstream areas. • Coordinate with existing and future land owners to align these proposed improvements with future development such as the private property within the Hunter Creek basin where proposed improvements will be tied to the single affected land parcel and will be the obligation of the land owner. 6.3 OPERATIONS AND MAINTENANCE RECOMMENDATIONS Aspen currently performs routine maintenance for City-owned storm sewer systems and those within their right-of-way. Aspen manages sediment and debris accumulation by periodically removing sediment from the inlets and storm sewer systems, and through street sweeping on a P179 I. 6-2 | Conceptual Design April 2015 regular basis, which reduces the potential for accumulation within the storm sewer system and promotes stormwater quality. However, there are a few maintenance issues related to dry wells, snow removal storage, and roadway grading. Recommendations to enhance the current level of service for these issues are noted below. • Provide regular maintenance of existing dry wells in the study area by cleaning out any accumulated silt and debris that affects the infiltration rate of collected stormwater in each well. • Provide regular maintenance to existing and proposed storm sewer networks to ensure the conveyance capacity is not hindered during a major precipitation event. • Provide designated snow storage areas that do not block any storm sewer systems, and that would not drain to private property. 6.4 PRIORITIZING AND PHASING Prioritization of the selected projects is shown in Table 6.1, and is based on an evaluation of the projects effectiveness in meeting the study objectives using ranking criteria. Several criteria and weighting percentages were selected to prepare the ranking of the suggested projects, and the project ranking scores were calculated. In addition, each project must be implementable, i.e., be constructible, financially feasible, and environmentally sound. Each project was evaluated by assigning a number between 0 and 4, where 0 = “no benefit” and 4 = “best benefit,” as follows: Buildings Removed from the Floodplain: 0 = none, 1 = value <0.9 project cost, 2 = value of 0.9 to 1.5 project cost, 3 = value of 1.5 to 2 project cost, and 4 = value > 2x project cost. (Value = Actual land cost taken from Aspen’s parcel dataset.) Public Safety (pedestrian and motorist safety, emergency response and government facilities): 0 = no improvement or N/A; 1 = local, residential street flooding within criteria; 2 = collector, commercial street flooding within criteria; 3 = arterial, business/commercial-industrial street flooding within criteria; and 4 = no highway or major transportation route overtopping, emergency response facilities and access protected. Water Quality Improvement Possible: 0 = none, no potential water quality location in basin; 2 = water quality location in basin but not near project or existing drainage system; 4 = water quality location along proposed project alignment. Requires Easement: 0 = easement cost > 3x project cost; 1 = easement cost > 1x project cost; 2 = easement cost > 0.5x project cost; 3 = easement cost > 0.25x project cost; 4 = no easement required. Cost Sharing Opportunities: 0 = none; 1 = < 10 percent of project costs paid by others; 2 = 10 to 25 percent of project costs paid by others; 3 = 25 to 50 percent of project costs paid by others; 4 = > 50 percent of project costs paid by others. Implementability: 0 = outside of jurisdiction and not on any planning horizon; 1 = project not on jurisdiction’s planning horizon but could be added; 2 = project is on planning horizon but needs funding; 3 = project is on multiple entities’ planning horizons waiting on known funding; 4 = project is planned, funded, and ready for execution. P180 I. April 2015 6-3 | Alternative Development Proposed project phasing over the next 10 years is suggested in Table 6.2. The proposed phasing is driven by project rank, sequence with related projects, and by financing and cost sharing opportunities with Pitkin County, CDOT, or other entities. Phasing is shown over only 10 years due to the relative average cost of the projects related to Aspen’s existing budget priorities (Reference 43). It should be revisited every year as part of Aspen’s budgeting process. P181 I. 6-4 | Conceptual Design April 2015 This page intentionally left blank P182 I. April 2015 6-5 | Conceptual Design Table 6.1 Project Ranking Matrix Proposed Stormwater Projects Location Land Cost (x$1,000) Total Cost (x$1,000) Buildings Removed from Floodplain Improves Public Safety Water Quality Improvement Possible Requires Easement Cost Sharing Opportunities Implement- ability Total Score (0 to 4) Rank (1 to 11) Comments 25% 20% 20% 15% 10% 10% 100% Hunter Creek Basin 1. Williams Woods Proposed System H05 to J02-H03 $54 $186 4 1 0 3 4 1 2.15 4 By development Combined Gibson Avenue and Neale Avenue & OK Flats Basins 1. River Bluff Townhomes Branch G08 to D08-G08 $112 $147 0 1 2 0 0 1 0.70 11 2. Lone Pine Rd. Outfall G13 and G05 to G06 $0 $169 0 1 2 4 0 1 1.30 10 3. Brown Ln. Branch and N12 Branch D25-G05 to D2-N12 and C86-G05 to C69-G05 $381 $533 0 1 0 1 0 1 0.45 12 4. Gibson Avenue Main Stem, N17 Branch, & G09 Branch N11 to OFALL-3 $0 $540 4 1 4 4 2 1 2.90 1 County cost-sharing for full project 5. Oklahoma Flats Outfall N25 to OFALL-6 $0 $54 4 1 0 4 0 1 1.90 6 6. Neale Avenue Storm System N21 to N23 $0 $123 0 1 4 4 0 1 1.70 8 7. King Street Branch N22 to D26-N23 $0 $43 0 1 2 4 0 1 1.30 10 Riverside McSkimming Basin 1. E. Cooper Avenue Outfall, Midland and Cooper Branch, & McSkimming Branch D06-R11 to OFALL-10 and D16-R17 to D10- R09 $150 $546 0 4 0 3 2 1 1.55 9 County cost-sharing for full project 2. E. Hopkins Outfall North Branch D20-R07 to OFALL-6 $0 $187 4 1 2 4 3 1 2.60 2 County cost-sharing for full project 3. E. Hopkins Outfall South Branch D25-R08 to D22-R10 $0 $199 4 1 0 4 0 1 1.90 6 Combined Eastwood and Stillwater Bridge Basins 1. Stillwater Bridge Basin Main Stem D13-S03 to OFALL-01 $0 $576 4 3 0 4 4 0 2.60 2 County Project 2. Stillwater Bridge Basin South Branch D02-S06 to D31-S10 $0 $377 4 1 0 4 4 0 2.20 3 County Project 3. Eastwood Main System D12-E02 to D32-E06 and D18-E02 $0 $258 0 4 0 4 3 1 1.80 7 County cost-sharing for full project, CDOT cost sharing along Highway 82 Note: All costs are in 2013 dollars. P183I. 6-6 | Conceptual Design April 2015 Table 6.2 Stormwater Capital Improvements Phasing 2016-2026 Rank (1 to 11) Proposed Stormwater Projects Basin Total Project Cost (x$1,000) Aspen Capital Costs Proposed Phasing (x$1,000) Potential Funding Sources Land Cost (x$1,000) Construction Cost (x$1,000) Total Cost (x$1,000) 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 1 Gibson Avenue Main Stem, N17 Branch, & G09 Branch Combined Gibson Avenue and Neale Avenue and OK Flats Basins $540 $0 $432 $432 $58 $374 County cost-sharing 2 E. Hopkins Outfall North Branch Riverside McSkimming Basin $187 $0 $187 $187 $187 County cost-sharing 2 Stillwater Bridge Basin Main Stem Combined Eastwood and Stillwater Bridge Basins $576 $0 $0 $0 Coordinate with Pitkin County to add to County's CIP. County Project 3 Stillwater Bridge Basin South Branch Combined Eastwood and Stillwater Bridge Basins $377 $0 $0 $0 Coordinate with Pitkin County to add to County's CIP. County Project 4 Williams Woods Proposed System Hunter Creek Basin $186 $0 $0 $0 Add information to permitting file for property to ensure inclusion in future development. By development 6 Oklahoma Flats Outfall Neale Avenue Basin $54 $0 $54 $54 $54 6 E. Hopkins Outfall South Branch Riverside McSkimming Basin $199 $0 $73 $73 $73 7 Eastwood Main System Eastwood Basin $258 $0 $121 $121 $121 County cost-sharing, CDOT cost sharing along Highway 82 8 Neale Avenue Storm System Neale Avenue Basin $123 $0 $123 $123 $123 9 E. Cooper Avenue Outfall, Mildland and Cooper Branch, & McSkimming Branch Riverside McSkimming Basin $546 $150 $396 $546 $53 $493 County cost-sharing 10 Lone Pine Rd. Outfall Gibson Avenue Basin $169 $0 $169 $169 $169 10 King Street Branch Neale Avenue Basin $43 $0 $43 $43 $43 11 River Bluff Townhomes Branch Gibson Avenue Basin $147 $112 $34 $147 $147 12 Brown Ln. Branch and N12 Branch Combined Gibson Avenue and Neale Avenue and OK Flats Basins $533 $381 $152 $533 $20 $513 TOTAL $3,938 $644 $1,783 $2,427 $54 $78 $513 $374 $260 $121 $166 $53 $493 $169 $147 Note: All costs are in 2013 dollars. P184I. April 2015 6-7 | Conceptual Design 6.5 FINAL PROPOSED COSTS The final proposed costs for each major basin within Aspen’s jurisdiction, and for which the city would be responsible, are presented in Table 6.3. Table 6.3 Final Proposed Project Costs for Aspen by Watershed (2013 Dollars) Proposed Projects by Major Basin Land Cost (x$1,000) Construction Cost (x$1,000) Total Cost (x$1,000) Combined Gibson Avenue and Neale Avenue & OK Flats Basins (10-year Conveyance) $494 $1,006 $1,500 Riverside McSkimming Basin (10-year Conveyance with Limited Easements) $150 $656 $806 Combined Eastwood and Stillwater Bridge Basins (10-year Conveyance with No Easements) $0 $121 $121 Total Cost of Proposed Projects $644 $1,783 $2,427 6.6 SELECTED PROJECTS BY BASIN The selected projects described below reflect only the proposed improvements that are within Aspen’s jurisdiction. The projects are shown on the conceptual drawings in Appendix G. 6.6.1 Combined Gibson Avenue and Neale Avenue & OK Flats Basins 10-year Conveyance Alternative To simplify the conveyance alternatives and minimize proposed storm sewer construction and required easements, the Gibson Avenue and Neale Avenue & OK Flats Basins were combined into one alternative. The selected alternative for this combined basin approach was the Combined Gibson Avenue and Neale Avenue & OK Flats Basins 10-year Conveyance Alternative with Minimal Easements. A new 18-inch RCP storm sewer system is proposed to begin in Teal Court at D25-G05 and will require an easement along the proposed alignment until the intersection with Williams Ranch Court. The system continues down Brown Lane where it intersects with the proposed Park Circle system. This reach is known as the Brown Lane Branch. This project is not highly ranked, but the project is tied to the mainstem Gibson Avenue improvements, which are dependent on the functionality of this system. The proposed system along Park Circle, known as the Main Gibson Avenue Basin and Neale Avenue & OK Flats Combined Main Stem, begins at D22-N13 as an 18-inch RCP along Park Circle and heads northwest toward Brown Lane. After connecting with the Brown Lane Branch, the system continues down Park Circle as an 18-inch RCP it takes a turn down Gibson Avenue and is upsized to a 24-inch RCP at D34-G07. The final reach of the combined main stem continues down Gibson Avenue as a 24-inch RCP to where it joins the existing outfall from a previous 24-inch CMP section at OFALL-3. This is the highest ranked project with significant floodplain improvement and water quality potential with no easements required. Two 18-inch storm sewers are proposed at G05 and G13. The G05 storm sewer is proposed to collect upstream runoff currently routed to an existing undersized cross-culvert. The G13 storm sewer is proposed to collect street runoff along Lone Pine Road from the intersection of the cross P185 I. 6-8 | Conceptual Design April 2015 culvert and the proposed 18-inch RCP storm system to D27-G06, where the system is proposed to be upsized to a 24-inch RCP system that ties into the existing 24-inch CMP. This existing piped section outfalls to the Roaring Fork River at OFALL-1. This is amongst the lowest ranked projects, because it requires an easement and there is no flooding to be resolved. A small separate 18-inch RCP storm sewer is proposed along East Francis Street in the Oklahoma Flats area. This system begins at N25 and follows East Francis Street to where it requires a private easement before discharging into the Roaring Fork River at OFALL-6. This Oklahoma Flats Outfall is amongst the highest ranked projects because it removes several buildings from the floodplain and resolves a known deficiency in the area. Another separate storm sewer, the River Bluff Townhomes Branch, is proposed to replace an assumed 8-inch polyvinyl chloride (PVC) pipe that discharges into a private detention area at D08-G08. An 18-inch RCP is proposed to collect flow from the existing ditch at G08 and discharge into this private detention area. This 18-inch RCP improvement will require a private easement. The detention pond outlet is an undersized 6-inch CMP but overflow is conveyed into a road side ditch along Red Mountain Road. An existing 12-inch CMP at D10-G10 collects the overflow and discharges to the Roaring Fork River at OFALL-2. This existing 12-inch CMP was shown to have 100-year capacity. This project is not highly rated due to the need for an easement; however, there is potential for water quality in the area. A separate 18-inch storm system is proposed along King Street that will connect to the Neale Avenue storm system at the King Street and Neale Avenue intersection to alleviate a known flooding area. The stretch along Neale Avenue from Gibson Avenue to Queen Street (N21 to N23) is proposed to be replaced by 36-inch RCPs to accommodate the incoming proposed storm sewer system from King Street. All other existing piped systems were shown to be able to convey the 10-year event with this combined configuration. The Neale Avenue Storm System project is dependent on the King Street Branch project for full functionality. Both projects are not highly rates because easements are required; however, there is potential for water quality improvements in the area. 6.6.2 Riverside McSkimming Basin 10-year Conveyance with Limited Easements Alternative The Riverside McSkimming basin has two main proposed storm systems: the East Cooper Avenue (OFALL-06) and East Hopkins Avenue outfalls (OFALL-10). The proposed East Hopkins Avenue Outfall consists of main southern and northern storm systems. The proposed northern system begins as an 18-inch RCP starting close to the beginning of Midland Park Place at D20-R07 where it runs along Midland Avenue to the intersection for Park Avenue and Regent Street at D31-R05. From this proposed system confluence, the piped system is upgraded to a 24-inch RCP. The 24-inch RCP northern system continues to the confluence with the southern system at the intersection of Park Avenue an East Hopkins Avenue at D22-R10 and then to the proposed storm sewer system outfall to the Roaring Fork River at OFALL-06. The East Hopkins Avenue southern system begins as an 18-inch RCP along Midland Avenue at D27-R05 and travels south to the intersection at East Hopkins Avenue and then to the west where it meets with the East Hopkins Avenue system at R10. The aesthetic ponds in the area that contribute to this proposed system (P04-R08 and P03-R08S) were modeled as full during the simulation to be conservative with the proposed storm system capacity and provided minimal P186 I. 6-9 | Conceptual Design April 2015 attenuation during all storm events. The East Hopkins Outfall North Branch is highly ranked due to removing floodplain areas, potential for water quality and cost sharing opportunities; however the downstream reach is dependent on the East Hopkins Outfall South Branch for full functionality. Therefore, the South Branch is phased with the North Branch. The proposed East Cooper Avenue storm sewer system begins at the lower end of Eastwood Drive at D06-R11 as an 18-inch RCP where it continues northwest along Eastwood Drive then cuts to the southwest through a private parcel to Highway 82 that will require an easement from D09-R09 to D10-R09. This reach from D09-R09 to Highway 82 (D10-R09) follows the natural grade of the hillside and results in a relatively steep slope that can result high storm water flow velocities. Final design of this section should include dissipaters to ensure the system is not damaged during high flows resulting in high velocities. The proposed system then continues northwest along Highway 82 as an 18-inch RCP as it turns into East Cooper Avenue and outfalls to the Roaring Fork River at OFALL-10. The proposed East Cooper Avenue storm system requires a 24-inch RCP from R19 to the outfall at OFALL-10. An 18-inch RCP is proposed to be jacked underneath East Cooper Avenue from R14 and connect to the East Cooper Avenue storm system at D12-R19 downstream of the intersection of McSkimming Road and East Cooper Avenue. An 18-inch RCP storm sewer is proposed at the downstream end of Lacet Lane at D16- R17 which will discharge into the main East Cooper Avenue storm sewer system at the intersection of Midland Avenue and East Cooper Avenue. This project is not highly ranked because but it does offer cost-sharing potential as well as improving public safety. 6.6.3 Combined Eastwood and Stillwater Bridge Basins 10-year Conveyance with No Easements Alternative The Eastwood Basin proposed storm system begins just downstream of the intersection of Northway Drive and Westview Drive at D12-E02 as an 18-inch RCP. The proposed system then heads south along Northway Drive where it turns toward the east along Roaring Fork Drive and follows the road until Highway 82 at D18-E02 where the City limits end. This project improves public safety along Highway 82 and has cost sharing potential, but it also requires an easement, so it is amongst the middle rankings. P187 I. 6-10 | Conceptual Design April 2015 This page intentionally left blank P188 I. SECTION SEVEN REFERENCES April 2015 7-1 | References 7 Section 6 SIX References Reference Number Reference (Author, Date, Title) 1. AMEC Earth & Environmental, Wright Water Engineers, Inc., Wenk & Associates. April 2010, Revised September 2014. Urban Runoff Management Plan, A Guide to Stormwater in the City of Aspen. . 2. American Society for Testing and Materials. 2009. Standard Specification for Perforated Concrete Pipe. Designation: C444 – 03. 3. Arattano, M. and Marchi, L. 2008. Systems and Sensors for Debris-flow Monitoring and Warning. Sensors, 8, pp. 2436-2452. 4. Arcement and Schneider. 1989. Guide for Selecting Manning’s Roughness Coefficients of Natural Channels and Floodplains. U.S. Geological Survey Water- Supply Paper 2339. 5. Benda, L. and Dunne, T. 1987. Sediment Routing by Debris Flow. Publication 165, Oxford, England, International Association of Hydrological Sciences. 6. Bentley Systems. 2009. FlowMaster V8i. Service Pack 3, 08.11.003.00. 7. Chang, S.Y. 2003. Evaluation of a system for detecting debris flows and warning road traffic at bridges susceptible to debris-flow hazard. In Rickenmann, D. and Chen, C-L (eds), Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment, Millpress, Rotterdam, Netherlands, pp. 731-742. 8. Chow, V.T. 1964. Handbook of Applied Hydrology, McGraw-Hill. 9. City of Aspen Engineering Department. June 2005. City of Aspen, Colorado, Design Standards. 10. City of Springfield, Missouri. March 8, 2007. Drainage Criteria Manual, Easements and Maintenance. 11. Colorado Climate Center, Climatological Data from Station 50370. 12. Colorado Climate Center, Climatological Data from Station 50372. 13. Colorado Water Conservation Board. September 2008. Floodplains and Stormwater Criteria Manual, Volumes 1 and 2. 14. Colorado Water Conservation Board. Accessed February 14, 2013 “Decision Support Systems”. http://cwcb.state.co.us/technical-resources/decision-support- systems/Pages/main.aspx. 15. Dunne, T. 1991. Stochastic aspects of the relations between climate, hydrology and landform evolution. Transactions, Japanese Geomorphological Union 12, pp. 1-24. 16. Federal Emergency Management Agency (FEMA). October 19, 2004. Flood Insurance Study, Pitkin County, Colorado and Incorporated Areas. Volumes 1-3. 17. FLO Engineering, Inc. January 1998. FLO-2D User’s Manual (and Program), Version 98.1. P189 I. 7-2 | Conceptual Design April 2015 18. Garcia, R., Lopez, J.L., Noya, M., Bello, M.E., Bello, M.T., Gonzalez, N., Paredes, G., Vivas, M.I., O’Brien, J.S. 2003. Hazard mapping for debris flow events in the alluvial fans of northern Venezuela. In Rickenmann, D. and Chen C-L. (eds), Debris-Flow Hazards, Mitigation: Mechanics, Prediction and Assessment. Millpress, Rotterdam, Netherlands, ISBN 907701778X. 19. Greminger, P. 2003. Managing the risks of natural hazards. In Rickenmann, D. and Chen CL. (eds), Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment. Millpress, Rotterdam, Netherlands, ISBN 907701778X. 20. Guzzetti, F., Peruccacci, S., Rossi, M., and Stark, C.P. 2007. Rainfall thresholds for the initiation of landslides in central and southern Europe. Meteorology and Atmospheric Physics, 98, pp. 239-267. 21. Huebl, J. and Fiebiger, G. 2005. Debris-flow mitigation measures. In Jakob, M. and Hunger, O. (eds), Debris-flow Hazards and Related Phenomena, Springer, 18, pp. 445-487. 22. Innovyze, Inc. 2011. InfoSWMM Suite 11.0, SP 1, Update #7. 23. Itakura, Y., Inaba, H., and Sawada, T. 2005. A debris-flow monitoring devices and methods bibliography. Natural Hazards and Earth System Sciences, 5, pp. 971-977. 24. Maidment, D.R. 1993. Handbook of Hydrology, McGraw-Hill. 25. Mizuyama. 2008. Sediment hazards and SABO works in Japan. International Journal of Erosion Control Engineering, v. 1, no.1, 4 p. 26. Mussetter Engineering, Inc. 2008. Cornet Creek Drainage Maintenance and Flood Mitigation Study, Colorado. Submitted to the Town of Telluride, Colorado, Public Works Dept., March, 107 p. 27. Mussetter Engineering, Inc. and Aquatic and Wetland Company. 1998. San Miguel River Corridor Restoration Plan. Submitted to the Town of Telluride. 28. National Oceanic and Atmospheric Administration (NOAA). November 1990. Climatological Data, Colorado, Volume 94. 29. National Research Council. 1982. Selecting a methodology for delineating mudslide hazard areas for the National Flood Insurance Program. National Academy of Sciences report by the advisory Board on the Built Environment, Washington, D.C. 30. NOAA. 2013. Precipitation-Frequency Atlas of the United States, Midwestern States, NOAA Atlas 14, Volume 8. 31. O’Brien, J.S. 2004. Simulating Mudflow Guidelines. Guidelines provided with FLO-2D model. 32. O’Brien, J.S., and Lenzotti & Fullerton Consulting Engineers, Inc. 1989. Flood Hazard Delineation on Alluvial Fans and Urban Floodplains. P190 I. April 2015 7-3 | References 33. OFEE, OFAT, ODEFP (Switzerland) ED. 1997. Prise en compte des dangers dus aux crues dams le cadre des activitiés de l’aménagment du territoire. Bienne, 1997. Office federal de l’économie de aux (OFEE), Office fédéral de l’économie des aue (OFEE), Office fédéral de l’aménagment du territoire (OFAT), Office federal de l’environment, de forets et du paysage (OFEFP) (In French) 34. Overton, D.E. and Meadows, M.E. 1976. Stormwater Modeling 35. Petrascheck, A. and Kienholz, H. 2003. Hazard assessment and mapping of mountain risks in Switzerland. In Rickenmann, D. and Chen C-L. (eds), Debris- Flow Hazards Mitigation: Mechanics, Prediction and Assessment, Millpress, Rotterdam, Netherlands, ISBN 907701778X. 36. Reneau, S.L. and Dietrich, W.E. 1991. Erosion rates in the Southern Oregon Coast Range: evidence of an equilibrium between hillslope erosion and sediment yield. Earth Surface Processes and Landforms 16, pp. 307-322. 37. Roth, A., Kästli, A., and Frenez, Th. 2004. Debris Flow Mitigation by Means of Flexible Barriers. Proceedings of the International Symposium Interpraevent, Riva del Garda, Italy, Klagenfurt: Interpraevent. 38. Russ Means, Colorado Department of Natural Resources. January 9, 2013. Email to Joel Jones of URS. 39. Simons, Li and Associates, Inc. and O’Brien, J.S. March 1989a. Flood Hazard Delineation for Cornet Creek, Telluride, Colorado. Submitted to the Federal Emergency Management Agency, Region VIII. 40. Simons, Li and Associates, Inc. and O’Brien, J.S. March 1989b. Supplemental Study - Flood Hazard Delineation for Cornet Creek, Telluride, Colorado. Submitted to the Federal Emergency Management Agency, Region VIII. 41. Tabata, S., Watari, M., Moriyama, H., and Shimojo, K. 2004. Improving wire net dams and capturing results. Research abstract, Sabo Frontier Foundation. 42. Takahashi, T. 2007. Debris Flow: Mechanics, Prediction and Countermeasures. Taylor & Francis, London, UK, 448 p. 43. The City of Aspen & Pitkin County Website. 2008. Accessed April 2015. http://www.aspenpitkin.com/Portals/0/docs/City/Finance/2015%20Budget%20Book %20-%20Web.pdf 44. The City of Aspen & Pitkin County Website. 2008. Accessed Dec. 2012. http://www.aspenpitkin.com/Departments/Street/Winter-Services/Snow-Plowing/. 45. United States Army Corps of Engineers (USACE). 1960. Engineering and Design – Runoff from Snowmelt. Engineering Manual 1110-2-1406. 46. United States Army Corps of Engineers. August 2009. Hydrologic Engineering Center, Computer Program HEC-HMS 3.4. 47. United States Army Corps of Engineers. September 1990. HEC-1 Flood Hydrograph Package, User’s Manual. P191 I. 7-4 | Conceptual Design April 2015 48. United States Army Corps of Engineers. January 2010. Hydrologic Engineering Center, Computer Program HEC-RAS 4.1.0. 49. United States Army Corps of Engineers. July 1993. Introduction and Application of Kinematic Wave Routing Techniques Using HEC-1. 50. United States Department of Agriculture (USDA), National Resources Conservation Service (NRCS). July 2004. Part 630 Hydrology, National Engineering Handbook, Chapter 11 Snowmelt. 210-VI-NEH. 51. United States Environmental Protection Agency (USEPA). Apri1 2011. EPA SWMM 5.0 Storm Water Management Model. 5.0.022. 52. United States Geological Survey and National Oceanic and Atmospheric Administration. 2005. Debris Flow Warning System—Final Report. Circular 1283, 47 p. 53. Urban Drainage and Flood Control District. January 1995. UDSWMM. 54. Urban Drainage and Flood Control District. January 2010. Colorado Urban Hydrograph Procedure 2005, Version 1.3.3. . 55. Urban Drainage and Flood Control District. 2011. Urban Stormwater Drainage Criteria Manual, Volume 1, pg. DP-23. 56. Urban Drainage and Flood Control District. Revised April 2008. Urban Stormwater Drainage Criteria Manual, Volume 2. 57. Volkwein, A., Wendeler, C., McArdell, B., Denk, M., Roth, A., and Wartmann, S. May 26 -30, 2008. Load Model for the Interaction between Debris Flow and Flexible Barriers. Extended Abstracts from the Proceedings of the 11th Congress Interpraevent, pp. 420-421. 58. Wei, F., Hu, K., and Cui, P. 2008. A decision support system for debris-flow hazard mitigation in towns based on numerical simulation: a case study at Dongchuan, Yannan Province. International Journal of Risk Assessment and Management, v. 8, no. 4, pp. 373-383. 59. Wendeler, C., McArdell, B.W., Rickenmann, D., Volkwein, A., Roth, A., and Denk, M., 2005. Field testing and numerical modeling of flexible debris flow barriers. 6 p. 60. Wendeler, C., McArdell, B.W., Volkwein, A., Denk, M., and Groner, E. 2008a. Debris flow mitigation with flexible ring net barriers—field tests and case studies. In de Wrachien, D., Brebbia, C.A., and Lenzi, M.A. (eds), Monitoring Simulation, Prevention and Remediation of Dense and Debris Flow II. WIT Press, pp. 23-31. 61. Wendeler, C., Volkwein, A., Roth, A., Herzog, B., Hahlen, N., and Wenger, M. 2008b. Hazard prevention using flexible multi-level debris flow barriers: Protection against debris flows installing 13 flexible barriers in the Milibach River (Canton Berne, Switzerland). Conference proceedings of the 2008 Interpraevent, v. 1, pp. 547-554. P192 I. April 2015 7-5 | References 62. Wireless Sensor Networks for Debris Flow Observation. Institute of Electrical and Electronics Engineers, pp. 615-617. 63. WRC Engineering, Inc. (WRC). 1998. Drainage Facility Capacity Analysis of the City of Aspen, Colorado. 64. WRC. November 2001. Surface Drainage Master Plan for the City of Aspen. 65. Wu, C.C. and Chang, Y.R. 2003. Debris-trapping efficiency of crossing-truss open-type check dams. In Rickenmann, D. and Chen C-L. (eds), Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment, Millpress, Rotterdam, Netherlands, ISBN 907701778X. P193 I. 7-6 | Conceptual Design April 2015 This page intentionally left blank P194 I. Appendices A through F are provided on the attached CD P195 I. P196 I. Appendix G Conceptual Plans P197 I. P198 I. 0+002+004+006+008+0010+0012+0012+020+002+004+006+008+0010+0012+0014+0016+0018+0020+0022+0024+0026+0026+500+002+004+00 6 +0 0 8 +0 0 9+930+001+002+003+003+740 + 00 2+ 00 4+00 5+410+002+002+830+000+160+000+80 0+000+290+000+322+450+001+002+00RIOGRANDEPLEMAINSTN GALENA ST N E A L E A V EQUE ENSTSOUTHAVEEFRANCISSTNSPRINGST MI NERSTRAI LRDGIBSONAVEWALNUTSTRACESTBRENDENCTLONEPINERDNMILLST KINGSTPARKCI RBROWNLNSILVERLODE DR COWENHOVENCTPARKCIRREPLACEEXISTINGSTORMSEWERWITH36"RCP,541LFREPLACEEXISTINGSTORMSEWERWITH24"RCP,820LFREPLACEEXISTINGSTORMSEWERWITH18"RCP,303LFPROPOSEDSTORMSEWER18"RCP,1110LFPROPOSEDSTORMSEWER24"RCP,118LFPROPOSEDSTORMSEWER18"RCP,690LFPROPOSEDSTORMSEWER18"RCP,2554LFPROPOSEDSTORMSEWER18"RCP,80LFPROPOSEDSTORMSEWER18"RCP,374LFPROPOSEDSTORMSEWER18"RCP,283LFPROPOSEDSTORMSEWER18"RCP,245LFPROPOSEDIMPROVEMENTSPLANSHEETOFSmuggler/HunterSurfaceDrainageMasterPlanStudyAreaBoundaryLegendProposedStormSewerProposedStormManhole0150'300'SCALE:1"=300'18PLANSHEETP199I. 0+002+004+006+00 7+100+00 2+00 4+006+00 8+009+740+001+002+003+004+005+006+007+008+009+0010+0011+0012+0013+0014+0015+0016+0017+0018+0019+0020+0021+0022+0023+0024+0024+240+001+002+003+004+005+006+007+00 8+00 9+00 9+410+000+570+000+68QUEENSTMIDLANDPARKPLMASCOTTELNARDMOREDRARDMORECTN RIVERSIDE AVE PARK AVE MIDLANDAVE EASTWOODDRCOOPERAVEHWY82CRYSTALLAKERD MCSKIMMINGRDRI VERSI DEDRHOPKINSAVEHOPKINSAVEROARI NGFORKDRREPLACEEXISTINGSTORMSEWERWITH24"RCP,456LFREPLACEEXISTINGSTORMSEWERWITH18"RCP,121LFREPLACEEXISTINGSTORMSEWERWITH18"RCP,235LFPROPOSEDSTORMSEWER18"RCP,380LFPROPOSEDSTORMSEWER18"RCP,1292LFPROPOSEDSTORMSEWER18"RCP,354LFPROPOSEDSTORMSEWER24"RCP,140LFPROPOSEDSTORMSEWER18"RCP,1540LFPROPOSEDSTORMSEWER18"RCP,55LFPROPOSEDSTORMSEWER18"RCP,310LFPROPOSEDSTORMSEWER18"RCP,940LFPROPOSEDIMPROVEMENTSPLANSHEETOFSmuggler/HunterSurfaceDrainageMasterPlanStudyAreaBoundaryLegendProposedStormSewerProposedStormManhole0150'300'SCALE:1"=300'28PLANSHEETP200I. ELEVATION (FT) ELEVATION (FT)STATION (FT)785078607870788078907900791079207930794078507860787078807890790079107920793079400+001+002+003+004+005+006+007+008+009+0010+0011+0012+0013+0014+0015+00LONE PINE RD. (MAIN STEM)ELEVATION (FT) ELEVATION (FT)STATION (FT)79107920793079407950796079707980791079207930794079507960797079800+001+002+003+004+005+006+007+008+00E. HOPKINS OUTFALL (SOUTH BRANCH)ELEVATION (FT) ELEVATION (FT)STATION (FT)792079307940795079607970798079908000801079207930794079507960797079807990800080100+001+002+003+004+005+006+007+008+009+0010+0011+00E. HOPKINS OUTFALL (NORTH BRANCH)ELEVATION (FT) ELEVATION (FT)STATION (FT)789079007910792079307940795078907900791079207930794079500+001+002+003+00LONE PINE RD. (G05 BRANCH)PROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET3HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P201I. ELEVATION (FT) ELEVATION (FT)STATION (FT)78407850786078707880789079007910792079307940795079607970798079908000784078507860787078807890790079107920793079407950796079707980799080000+001+002+003+004+005+006+007+008+009+0010+0011+0012+0013+0014+0015+0016+0017+0018+0019+0020+0021+0022+0023+0024+0025+0026+0027+00GIBSON AVE. MAIN STEMPROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET4HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P202I. ELEVATION (FT) ELEVATION (FT)STATION (FT)7900791079207930794079507900791079207930794079500+001+002+003+00ELEVATION (FT) ELEVATION (FT)STATION (FT)78507860787078807890785078607870788078900+001+002+003+00GIBSON AVE. MAIN STEM(G09 BRANCH)GIBSON AVE. MAIN STEM(N17 BRANCH)ELEVATION (FT) ELEVATION (FT)STATION (FT)784078507860787078807890790078407850786078707880789079000+001+002+003+004+005+00OKLAHOMA FLATS OUTFALLELEVATION (FT) ELEVATION (FT)STATION (FT)790079107920793079407950796079007910792079307940795079600+001+002+003+004+005+00KING ST. BRANCHELEVATION (FT) ELEVATION (FT)STATION (FT)7880789079007910792079307940795079607880789079007910792079307940795079600+001+002+003+004+005+006+007+00NEALE AVE STORM SYSTEMPROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET5HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P203I. ELEVATION (FT) ELEVATION (FT)STATION (FT)79407950796079707980799080007940795079607970798079908000-2+00-1+000+001+002+003+004+005+006+007+008+009+0010+0011+00BROWN LN. BRANCHELEVATION (FT) ELEVATION (FT)STATION (FT)8020803080408050806080708080809081008110812081308140815081608020803080408050806080708080809081008110812081308140815081600+001+002+003+004+005+006+007+008+009+0010+0011+00EASTWOOD MAIN STEMELEVATION (FT) ELEVATION (FT)STATION (FT)7940795079607970798079907940795079607970798079900+001+002+00BROWN LN. BRANCH(N12 BRANCH)PROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET6HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P204I. ELEVATION (FT) ELEVATION (FT)STATION (FT)792079307940795079607970798079908000801080208030804080508060807079207930794079507960797079807990800080108020803080408050806080700+001+002+003+004+005+006+007+008+009+0010+0011+0012+0013+0014+0015+0016+0017+0018+0019+0020+0021+0022+0023+0024+0025+0026+00E. COOPER AVE. MAIN STEMPROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET7HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P205I. ELEVATION (FT) ELEVATION (FT)STATION (FT)79407950796079707980794079507960797079800+001+002+003+00ELEVATION (FT) ELEVATION (FT)STATION (FT)79908000801080208030799080008010802080300+001+002+003+00E. COOPER AVE. MAIN STEM(MIDLAND AND COOPER BRANCH)E. COOPER AVE. MAIN STEM(MCSKIMMING BRANCH)ELEVATION (FT) ELEVATION (FT)STATION (FT)78707880789079007910787078807890790079100+001+002+003+00RIVER BLUFF TOWNHOMES BRANCHPROPOSEDIMPROVEMENTSSHEET OFSMUGGLER/HUNTERSURFACE DRAINAGEMASTER PLAN8PROFILE SHEET8HORIZONTAL SCALE: 1"=200'VERTICAL SCALE: 1"=20'P206I. Elected Officials Transportation Committee (EOTC) Thursday, March 23, 2017- 4:00pm Location-Aspen City Hall-Council Chambers Pitkin County to Host and Chair Meeting __________________________________________________________________________________________ I. 4:00 - 4:10 REVIEW OF DECISIONS REACHED AT THE JANUARY 19, 2017 MEETING John D. Krueger-City of Aspen II. 4:10 - 4:20 PUBLIC COMMENT (Comments limited to three minutes per person) III. 4:20 - 4:30 CONFIRMATION OF 2017 MEETING DATES John D. Krueger-City of Aspen Decision Needed: Confirmation of 2017 Meeting Dates IV. 4:30 – 6:00 UPPER VALLEY MOBILITY STUDY Ralph Trapani, Joe Kracum and Phil Hoffman- Parsons Decision Needed: None-Information Only V. 6:00 – 6:30 DISCUSSION OF SNOWMASS VILLAGE CONNECTIONS TO BUS RAPID TRANSIT SERVICE David Peckler-Snowmass Decision Needed: None-Discussion Only VI. 6:30 – 6:45 UPDATES & FUTURE AGENDA ITEMS P207 II. ELECTED OFFICIALS TRANSPORTATION COMMITTEE (EOTC) January 19, 2017 Aspen-Council Chambers Aspen - Host & Chair AGREEMENTS & DECISIONS REACHED Elected Officials in Attendance: Aspen - 2 Pitkin County - 5 TOSV - 5 Adam Frisch Steve Child Markey Butler Bert Myrin Greg Poschman Alyssa Shenk Ann Mullins George Newman Bill Madsen Patti Clapper Bob Sirkus Rachel Richards Tom Goode Absent: Aspen: Steve Skadron, Art Daly Pitkin County: None Snowmass: None ______________________________________________________________________________ Agreements & Decisions Reached: I. REVIEW OF DECISIONS REACHED AT THE JANUARY 19, 2017 MEETING John D. Krueger-City of Aspen No comments were made. II. PUBLIC COMMENT Jay Maytin provided comment on his idea to alleviate traffic going out of town in the afternoon by opening the bus lane going down valley on the north side of the highway from the roundabout to Buttermilk to automobiles. The bus lane is a regulated and federalized component of the Record of Decision, FEIS, BRT and was part of a vote on the use of open space. Opening the bus lane to automobile traffic is not possible. III. CONFIRMATION OF 2017 MEETING DATEs John D. Krueger-City of Aspen Decision Reached: Confirmation of the proposed 2017 meeting dates. The meeting dates for 2017 were confirmed as: • January 19, 2017 Aspen • March 23, 2017 Pitkin County 1 P208 II. • June 15, 2017 Snowmass • October 19, 2017 Aspen IV. UPPER VALLEY MOBILITY STUDY (UVMS) Ralph Trapani, Joe Kracum and Phil Hoffman-Parsons No decision Needed: Information only The meeting objective was to provide a review of the project purpose and need, scope an update and inspire a visioning process. The project purpose and need is to improve mobility between Brush Creek and Rubey Park, reduce the number of buses and congestion in Aspen, enhance transit and support current policies on transportation. The project scope provides transit ridership forecasting, an analysis of LRT and BRT from Brush Creek to Rubey Park on the preferred alternative alignment and cost estimating of the LRT and BRT alternatives. The October meeting provided an update on potential technology solutions as they may apply to the project. The January meeting included a review of the ridership forecast, current bus operations, a discussion of the BRT and LRT alignment alternatives and traffic impacts. At the March meeting, there will be an update on the UVMS schedule, ridership forecasts for both LRT and BRT alternatives and capital, operations and maintenance costs of both LRT and BRT alternatives V. UPDATES None VI. FUTURE AGENDA ITEMS UVMS Study-Costs 2 P209 II. EOTC Transit Project Funding Estimate or Actual Budget Budget Plan Plan Plan Plan 2015 2016 2017 2018 2019 2020 2021 FUNDING SOURCES: a)Pitkin County 1/2% sales tax 4,929,637 5,033,000 5,159,000 5,288,000 5,460,000 5,637,000 5,820,000 b)Pitkin County 1/2% use tax 1,462,424 1,293,000 1,225,000 1,262,000 1,300,000 1,339,000 1,379,000 c)Investment income & misc.56,747 79,000 60,000 84,000 76,000 102,000 141,000 d)Federal Lands Access Program (FLAP) grant 1,900,000 Total Funding Sources 6,448,808 6,405,000 6,444,000 8,534,000 6,836,000 7,078,000 7,340,000 FUNDING USES: 1)Use tax collection costs 63,538 70,432 56,257 57,945 59,683 61,474 63,318 2)Administrative cost allocation & meeting costs 21,383 21,311 24,394 25,126 25,880 26,656 27,456 3)Cab ride in-lieu of bus stop safety imprvs 3,561 9,000 6,000 6,000 6,000 6,000 6,000 4)X-Games transit subsidy 115,000 115,000 115,000 115,000 115,000 115,000 115,000 5)Brush Creek Intercept Lot operating costs 15,046 36,000 30,000 30,900 31,800 32,800 33,800 6)RFTA contribution (81.04% of 1/2% sales tax)3,994,977 4,078,743 4,180,854 4,285,395 4,424,784 4,568,225 4,716,528 7)No-fare Aspen-Snowmass-Woody Creek bus service - year-round 621,658 621,658 615,726 640,400 666,000 692,600 720,300 8)Grand Ave Bridge construction - transit mitigation funding 335,000 9)Buttermilk lot paving 233,007 46,993 10)Valley parking study - RFP scoping 7,957 11)Basalt pedestrian underpass 750,000 Projects funded from Savings for greater Aspen Area 12)Rubey Park final design, land use & permitting 142,292 16,078 13)Rubey Park construction 4,168,777 731,223 14)Entrance-to-Aspen transportation options study 414,004 15)Cell phone transportation data collection 70,000 New Budget Request 16)WE-cycle operational support 100,000 Future projects 17)Brush Creek Park and Ride improvements (FLAP grant) 3,900,000 18)Buttermilk pedestrian crossing design & preliminary engineering 800,000 Total Uses 9,387,196 6,980,442 5,463,231 9,860,766 5,329,147 5,502,755 5,682,401 EOTC ANNUAL SURPLUS/(DEFICIT)(2,938,388) (575,442) 980,769 (1,326,766) 1,506,853 1,575,245 1,657,599 EOTC CUMULATIVE SURPLUS FUND BALANCE 7,225,318 6,649,876 7,630,645 6,303,879 7,810,733 9,385,978 11,043,577 a)sales tax 7.9%2.1%2.5%2.5%3.25%3.25%3.25% b)use tax 44.9%-11.6%-5.3%3.0%3.0%3.0%3.0% c)investment earnings rate 0.5%0.7%0.9%1.1%1.2%1.3%1.5% Revenue projections: 3 P210II. Estimate or - Actual Budget Budget Plan Plan Plan Plan 2015 2016 2017 2018 2019 2020 2021 DISTRIBUTION OF ANNUAL SURPLUS (excludes projects funded from savings funds)1,372,681 655,863 980,769 (1,326,766) 1,506,853 1,575,245 1,657,599 25% to Snowmass Village Savings until restored to $6,278,787 343,170 163,966 245,192 (331,691) 376,713 227,633 - remainder to Aspen Savings 1,029,511 491,897 735,577 (995,074) 1,130,140 1,347,613 1,657,599 Savings Fund for greater Snowmass Village Area plus reimbursement of advance to capital pool 343,170 163,966 245,192 (331,691) 376,713 227,633 - Savings Fund for greater Snowmass Village Area ($6,278,787 max)5,596,974 5,760,940 6,006,132 5,674,441 6,051,154 6,278,787 6,278,787 Savings Fund for greater Aspen Area Annual surplus remaining after reimbursement of advances - 381,642 735,577 (995,074) 1,130,140 1,347,613 1,657,599 plus reimbursement for $250,000 pedestrian crossing funding 114,783 - plus reimbursement of advance to capital pool 914,728 110,255 less Rubey Park funded from Aspen Savings (4,311,069) (747,301) less ETA and cell phone study funded from Aspen Savings (484,004) Savings Fund for greater Aspen Area 1,628,344 888,936 1,624,513 629,439 1,759,579 3,107,191 4,764,790 Advances from Aspen and Snowmass Village Savings Funds remaining balance to reimburse Snowmass Savings for advance to capital pool 681,813 517,847 272,655 604,346 227,633 - - remaining balance to reimburse Aspen Savings for advance to capital pool 110,255 - - - - - - 4 P211II. MEMORANDUM TO: The Elected Officials Transportation Committee (EOTC) FR: John D. Krueger, City Of Aspen Meeting Date: March 23, 2017 RE: 2017 EOTC Meeting Dates The following meeting dates were approved for 2017. • January 19, 2017 Special Meeting – Aspen to Host & Chair • March 23, 2017 Pitkin County-Host & Chair • June 15, 2017 Snowmass-Host & Chair • October 19, 2017 Aspen-Host & Chair Are these dates still good for 2017? 5 P212 II. MEMORANDUM TO: Elected Officials Transportation Committee (EOTC) FR: John D. Krueger-City of Aspen METTING DATE: March 23, 2017 RE: Upper Valley Mobility Study (UVMS) ______________________________________________________________________ No Decision Needed: Information only Parsons will be presenting ridership and cost information relative to the Upper Valley Mobility Study (UVMS). The meeting packet includes a copy of the scope of work and schedule previously approved by the EOTC. The presentation will be provided at the meeting. At the October 2016 EOTC Meeting, the UVMS presentation included the “Project Purpose and Need” which is to: • Improve mobility between Brush Creek and Rubey Park • Reduce the number of buses and congestion in Aspen • Enhance transit service to make it faster, more reliable and attractive for users • Support City of Aspen and Pitkin County transportation plans and policies The technology section of the presentation included a discussion of BRT and LRT options for vehicles/manufacturers and propulsion and technology comparison of BRT and LRT. The January 2017 EOTC meeting included a UVMS presentation on: • Ridership Forecasting Approach • Current Bus Operations • Alternatives Discussion o BRT Alternative o LRT Alternative o LRT Traffic Impacts 6 P213 II. At the March 23 2017 meeting, the following information will be presented: • Update on the UVMS schedule • Ridership forecasts for both LRT and BRT Alternatives • Capital, operations and maintenance costs of both LRT and BRT alternatives 7 P214 II. TO 03 - ETA Schedule v2 - 9/23/16 month:1 2 3 4 5 6 7 8 9 10 11 Task #Task Name Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 1A Project Kick Off Meeting 1B 10 TAC Meetings 1C 5 EOTC Meetings 1D 6 Individual Meetings 1E 2 Public Workshop (Aspen) 2 Compile Background Data 3A Fixed Guideway Scope 1 Fixed Guideway Scope - Initial Design 2 Fixed Guideway Scope - Technology Scan 3B Fixed Guideway Ridership 3C Fixed Guideway Triggers 3D Fixed Guideway Costs 3E Fixed Guideway Funding 1 Fixed Guideway Funding - Refined Design 3F Fixed Guideway Sustainability 3G Fixed Guideway Implementation Plan 4A Bus Scope 1 Bus Scope - Initial Design 2 Bus Scope - Technology Scan 4B Bus Ridership 4C Bus Triggers 4D Bus Costs 4E Bus Funding 1 Bus Funding - Refined Design 4F Bus Sustainability 4G Bus Implementation Plan 5 Compare Alternatives 5 Documentation 8 P215II. Entrance to Aspen Transportation Options Study Task Order XX Scope of Work Background As a supplement to the ITSP, RFTA has asked Parsons to analyze a fixed guideway (light rail) transit connection versus the forecasted bus rapid transit system currently in place in regards to ridership, capital expenditures, and operations and maintenance costs from Brush Creek to Rubey Park, Aspen. Existing data and reports will be utilized. No new alignment studies will be conducted for the fixed guideway (light rail) transit system or bus rapid transit alignments within the study area. All alignments will be as per the preferred alternative from the Record of Decision of the Entrance to Aspen (ETA) document, 1996. Existing data will be updated based on Reports noted in Task 2 Included in the transit evaluation are the following components: •Transit systems (fixed guideway and BRT) scope and phasing •Scan for emerging transit technologies •Triggers for implementation (bus ridership, numbers of buses in town, cost effectiveness) •Capital and operating costs •Funding opportunities and constraints •Implementation plan As part of the analysis, Parsons will examine transit system impacts to traffic on SH82, including at the intersections of SH82 and Brush Creek Road, at the Maroon Creek roundabout, and local city street intersections in Aspen. This scope of work does not include analyzing any other mode of transportation besides light rail transit and bus rapid transit as described in the Preferred Alternative. It does not include identification and screening of any other alternatives. Please see the New Transportation Alternatives and Full Screening Study Scope of Work (“Large Scope) for the tasks involved with identifying and screening other alternatives. The EOTC may also direct that other specific mode alternatives be included for screening or for screening and comparison. If that is the case, the schedule and cost of this work program will be adjusted accordingly. Schedule It is anticipated that Notice to Proceed will be August 1, 2016. This task order will be executed in parallel with Stage II and III of the RFTA ITSP to allow for efficient use of staff and management of data sets. The project duration is for a 10 month contract period, anticipated to end on June 1, 2017. 9 P216 II. Task 1. Project Initiation and On-Going Management This task order will be contracted through the RFTA master contract with Parsons. Parsons will be managed by Pitkin County staff. Our point-of-contact with Pitkin County will be Brian Pettet, Director of Public Works. EOTC staff from member jurisdictions will form a Technical Advisory Committee (TAC) to provide direction and oversight for this task order. RFTA will provide a member to the TAC. The purpose of this task is to initiate the work of the ETA task, and then manage the budget, schedule and resources throughout the duration of the work. Parsons will have an initial kick-off meeting with the TAC to discuss the scope of work and associated schedule. During this initial kick-off meeting, we will discuss inputs and procedures. A detailed schedule will be developed for and reviewed at the initial kick-off meeting. Meetings Anticipated meetings will be conducted as follows: •TAC Meetings- Monthly (assume 10) •EOTC Meetings-Bi-monthly (assume 5 meetings) •Meeting with individual EOTC jurisdictions- 2 meetings each, total of 6 meetings •Public Open Houses in Aspen (2) This task will incorporate all hours necessary to complete the on-going management of the task order, including administration tasks and preparing for and conducting meetings. Deliverables for Task 1 are as follows: A. Meeting materials B. Project Meeting Minutes; PDF version C. Monthly invoices and progress reports Task 2. Compile Background Data The purpose of this task is to gather and synthesize data from previous reports. These reports include: •CIS •SH82 ROD •ETA ROD 10 P217 II. •ETA Re-Evaluation •ETA Supplemental O&M Analysis, 1999 •Various Parsons and City of Aspen studies conducted in area Data to be collected includes alternative alignments, forecasts, cost and financial information. Data synthesis will include a discussion about the influence of the Record of Decision (ROD) on studied alternatives (Risks and Opportunities as related to the Preferred Alternative) Deliverables for Task 2 are as follows: D. Summary and synthesis of data compiled, PDF Task 3. Develop Fixed Guideway Transit Alternatives The purpose of this task is to develop a fixed guide way alternative using light rail transit or similar system to compare against the bus rapid transit system to be developed under Task 4, in terms of ridership, capital expenditures, and operations and maintenance costs from Brush Creek to Rubey Park, Aspen. Subtask 3A: Fixed guideway scope and phasing •alignments and structure delineation – will be as developed in ROD and updated •station locations - (1) as developed in ROD, (2) new stations •system types - (1) advanced LRT with no overhead lines/battery powered, (2) LRV/streetcar •worldwide scan (literature search) for any emerging fixed guideway technologies. •examine fixed guideway impacts to traffic on SH82, including at the intersections of SH82 and Brush Creek Road, at the Maroon Creek roundabout, and local city street intersections in Aspen Subtask 3B: Ridership forecasts for fixed guideway •forecasted growth •transfer penalties at both Brush Creek and Rubey Park •airport expansion interface Subtask 3C: Triggers for implementation •bus ridership •numbers of buses in town •cost effectiveness Subtask 3D: Update capital and operating costs •capital expenditures - update cost estimate and conduct risk based cost analysis •operating costs - develop operating and maintenance costs 11 P218 II. o new maintenance facility Subtask 3E: Evaluate funding opportunities and constraints •project delivery including P3 options •federal •state •local •farebox Subtask 3F: Address sustainability •energy usage/savings •air quality benefits •traffic reduction/LOS improvements •safety improvements (fewer car crashes) Subtask 3G: Implementation plan •report to summarize results of Task 3 Deliverables for Task 3 are as follows: E. Implementation Plan report summarizing the fixed guideway transit system, PDF Task 4. Develop Bus Rapid Transit Alternatives The purpose of this task is to develop a bus rapid transit alternative using to compare against the fixed guideway transit system to be developed under Task 3, in terms of ridership, capital expenditures, and operations and maintenance costs from Brush Creek to Rubey Park, Aspen. The bus rapid transit alternative will be based on the existing system, but modified to accommodate future growth and technologies. Subtask 4A: Busway scope and phasing •alignments and structure delineation o examine existing alignment (bus in mixed transit from Maroon Creek roundabout to Rubey Park) o examine alignments for the bus rapid transit system as per the preferred alternative from the Record of Decision of the Entrance to Aspen document, 1996 o examine guided bus-ways •station locations - (1) existing stations, (2) new stations 12 P219 II. •system type - (1) electric, (2) driverless •worldwide scan (literature search) for any emerging Bus technologies. •examine bus rapid transit impacts to traffic on SH82, including at the intersections of SH82 and Brush Creek Road, at the Maroon Creek roundabout, and local city street intersections in Aspen Subtask 4B: Ridership forecasts for fixed guideway •forecasted growth •transfer penalties at both Brush Creek and Rubey Park •airport expansion interface Subtask 4C: Triggers for implementation •bus ridership •numbers of buses in town •cost effectiveness Subtask 4D: Update capital and operating costs •capital expenditures - update cost estimate and conduct risk-based cost analysis •operating costs - develop operating and maintenance costs o expanded maintenance facility Subtask 4E: Evaluate funding opportunities and constraints •project delivery including P3 options •federal •state •local •farebox Subtask 4F: Address sustainability •energy usage/savings •air quality benefits •traffic reduction/LOS improvements •safety improvements (fewer car crashes) Subtask 4G: Implementation plan •report to summarize results of Task 4 Deliverables for Task 4 are as follows: F. Implementation report summarizing the bus rapid transit system, PDF 13 P220 II. Task 5. Compare Transit Alternatives The purpose of this task is to compare the fixed guideway transit system alternative developed under Task 3 to the bus rapid transit system alternative developed under Task 4. If any emerging technologies are deemed appropriate by the TAC, they will be included in the comparison. Parsons will make a side- by-side comparison, and provide quantitative and qualitative discussions for each evaluation criteria. Criteria will include a discussion of how alternatives relate to the current EIS and ROD, and how they relate to and impact RFTA. Deliverables for Task 5 are as follows: F. Alternative comparison table, PDF Task 6. Close Out of ETA Task Order The purpose of this task is to close out the work of the ETA Task Order. Parsons will populate the project deliverables checklist to ensure all deliverables were submitted to RFTA. Parsons will also provide final invoicing for the task order. Deliverables for Task 6 are as follows: G. Final Invoice for task order; PDF version H. Populated Project Deliverables Checklist; PDF version Task 1 Project Initiation and On-Going Management Task 2 CompiIe Background Data Task 3 Develop Fixed Guideway Transit Alternatives Task 4 Develop Bus Rapid Transit Alternatives Task 5 Compare Transit Alternatives Task 6 Close out 14 P221 II. AGNEDA ITEM SUMMARY EOTC MEETING DATE: March 23, 2017 AGENDA ITEM TITLE: Snowmass Village Connections to Bus Rapid Transit Service STAFF RESPONSIBLE: David Peckler ISSUE STATEMENT: Snowmass Village wants to begin discussions with the entire Elected Officials Transportation Committee (EOTC) on the potential for making improvements to the regional service connections between Snowmass Village and the Intercept lot to provide enhanced service to the VelociRFTA (BRT) service. During the spring, summer and fall the regional connections along the trunk line between Snowmass Village and the Intercept lot are every 30 minutes (this drops to once an hour during portions of the weekend daytime service in spring and fall.) Snowmass Village would like to receive EOTC support to explore the potential of increasing regional service from Snowmass Village to the Intercept lot to approximately every 15 minutes during periods when the BRT service is operating. This headway would provide a commensurate level of service that other municipalities within the EOTC receive and would make travelling on the BRT service more viable going to/from Snowmass Village. BACKGROUND: BRT service began in the fall of 2013. This service improvement was confined to the Highway 82 corridor and there were no changes to the regional service other than some “Direct” buses being switched to BRT service. In the winter it became apparent that merging the BRT service with the Free Skier Shuttles could improve connections between Snowmass and the Intercept lot, and now the fifteen minute headway is part of the regional winter service plan. Snowmass Village would like to see this improvement extended into the other seasons during the hours of BRT operation. Snowmass Village views this as a logical and equitable progression that is worth exploring with the EOTC members. BUDGET IMPACT: Many details are still to be developed. Staff is working to determine the cost of this service expansion using regional service in the summer and local service in the spring and fall. The local service plan in the spring and fall is to use 45 minute loops to make connections to the BRT service at the Intercept lot under the existing service contract. This approach is expected to provide a minimum of 25% savings to the regional service costs. The summer service improvements would be operated by the regional service. RECOMMENDED EOTC ACTION: No formal action is needed at this time. Once the analysis is complete, it will be brought back to the EOTC for formal consideration. 15 P222 II. RFTA 2014 Regional Travel Patterns Update4 RFTA 2014 Regional Travel Patterns Update 1 REGIONAL Travel Patterns Community Profile ROARING FORK AND COLORADO RIVER VALLEY Regional Travel Patterns Profile 2004 2014 Population1 71,037 82,2272 Population residing year-round 94%94% Lived in region > 1 year 92%93% Households with children under 16 31%31% Households receiving housing assistance 12%12% Median annual household income $75,0003 $66,000 HOUSING/DEMOGRAPHIC DATA O V E R V I E W O T H E R T R I P S ABOUT THE PROJECT EA GL E PI TK INGA RF IE LD Rural West Garfield County Rural East Garfield County Rural East Pitkin County Rural West Pitkin County Rural Southwest Eagle County Missouri Heights/ Lookout Mtn. West Aspen Snowmass Village Battlement Mesa Aspen Airport/Woody Creek El Jebel Downtown/ West Glenwood Springs South Rifle East Aspen Silt Basalt New CastleCentral Rifle Carbondale Parachute North Rifle Glenwood Meadows/ Red Mtn. §¨¦70 ¬«13 ¬«325 MESA GARFIELD EAGLE PITKIN DELTA GUNNISON LAKE RIO BLANCO CHAFFEE SUMMIT 0 7.5 Miles !(82 §¨¦70 41% 23% 9% 18% 9% 56% 14% 8% 19% 4% 0% 10% 20% 30% 40% 50% 60% Drove Alone Carpool Bus Walk Bike Personal Trips Mode Share Summer Winter Personal Trips Mode Share Work-Related Trips Mode Share 53% 19% 9% 15% 3% 56% 14% 8% 19% 4% 0% 10% 20% 30% 40% 50% 60% Drove Alone Carpool Bus Walk Bike Winter Personal Trips Mode Shift 2004 2014 Winter Personal Trips Mode Shift Winter Work-Related Trips Mode Shift PERSONAL TRIPS OF RESIDENTS WORK-RELATED TRIPS OF WORKERS 58% 14% 10% 9% 9% 64% 17% 8% 9% 3% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Work-Related Mode Share Summer Winter The Roaring Fork Transportation Authority (RFTA) conducted a regional travel patterns study in 2014 of the Colorado River Valley and Roaring Fork Valley from Parachute to Aspen. Previous studies were completed in 1998 and 2004. The project was a cooperative effort of RFTA, Colorado DOT, and area counties and municipalities. The project was conducted to provide local jurisdictions and planning agencies with information on travel demand within the study area. This includes information about current and future needs for motor vehicles, for public transit and for walking and bicycling. Data from the study was also used to develop travel forecasts and will help companies and agencies design commuter support programs to address needed changes in travel choices. The data collection methodology included two rounds of surveys, a winter and summer survey. The winter survey targeted employees and employers within the study area. The summer survey targeted residents. A total of 1,679 surveys of residents and employees were collected (1,352 in the winter and 327 in the summer) and 110 employer surveys were completed. The region was divided into 23 transportation analysis zones (TAZs) and all data will be available at the TAZ level. A comprehensive report of the study’s finding will be available through RFTA in early 2015. Transportation Analysis Zone Map of the Region REGIONAL GEOGRAPHY The regional travel patterns profile includes data col- lected from all of Garfield and Pitkin Counties and the portion of Eagle County within the Roaring Fork Valley. This includes all 23 transportation analysis zone(s) (TAZs) mapped below. 1. U.S. Census Bureau 2. 2012 Population (American Community Survey) 3. Inflation adjusted for 2014 dollars Mode share is displayed above for the two trips purposes other than commute trips (shown on page 2 in the “Com- muting” section). These include work-related trips, which are trips made during work by employees for business purposes, and personal trips, which cover all other trips that are not commute or work-related trips. 63% 15% 11% 9% 2% 64% 17% 8% 9% 3% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Winter Work-related Mode Shift 2004 2014 Transportation Analysis Zones (TAZs) Parachute Missouri Heights/ Lookout Mtn. Battlement Mesa Carbondale North Rifle El Jebel Central Rifle Basalt South Rifle Rural Southwest Eagle County Rural East Garfield County Rural West Pitkin County Rural West Garfield County Rural East Pitkin County Silt Snowmass Village New Castle Aspen Airport/ Woody Creek Downtown/ West Glenwood Sprgs.West Aspen Glenwood Meadows/ Red Mtn.East Aspen South Glenwood Springs Data for 2014 was collected from the 2014 Winter and Summer Roaring Fork Transportation Authority (RFTA) Travel Patterns Survey unless otherwise indicated. Data for 2004 was collected from the 2004 Local & Regional Travel Patterns Survey unless otherwise indicated. 16 P223II. RFTA 2014 Regional Travel Patterns Update2 RFTA 2014 Regional Travel Patterns Update 3 REGIONAL Travel Patterns Community Profile REGIONAL Travel Patterns Community Profile % of Residents who . . .2004 2014 Own a bus pass/stored value card 30%28% Employer provided buss pass/ value card 15%18% Live within 5 blocks of a bus stop 52%43% Live over a mile from nearest bus stop 29%34% Have taken VelociRFTA in last 30 days N/A 35% Have taken other bus in last 30 days 38%39% TRANSIT DATA VelociRFTA 42% Other Bus 40% Both 18% Bus Used For Typical Commute Bus used for typical commute How bus riders got to/from the bus TRANSIT ACCESS Summer bicycle mode share by trip purpose BICYCLING 2004 2014 2012 Worker population2 43,0004 48,3855 Vehicle available for commuting 85%87% Average commute distance 15 miles 16 miles Average commute time 23 mins 25 mins Work and live in same community 41%37% Workers with free parking at work 81%91% COMMUTING DATA C O M M U T T I N G 93% 1% 1% 1% 1% 2% 87% 2% 2% 1% 1% 7% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Do not telecommute Less than 1 day a month 1-3 days per month 1 day per week 2 days per week 3 or more days a week Telecommute Mode Shift 2004 2014 Telecommute Mode Shift Commute Mode Share by Parking Type at Work* T R A N S I T W A L K / B I K E 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Daily Ridership March July +28% +53% RFTA daily ridership 2004-201452% 15% 17% 9% 8% 62% 12% 19% 5% 2% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Commute Mode Share Summer Winter 2014 Commute Mode Share 71% 12% 8% 6% 2% 42% 20% 34% 3% 1% 31% 5% 61% 1% 1% 0% 10% 20% 30% 40% 50% 60% 70% 80% Drove Alone Carpool Bus Walk Bike Mode Share by Bus Pass Ownership No Bus Pass Stored Value Card Bus Pass Commute Mode Share by Bus Pass Ownership* 64% 16% 12% 6% 2% 62% 12% 19% 5% 2% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Winter Commute Mode Shift 2004 2014 Winter Commute Mode Shift Commute Mode Share by Employer Provided Bus Pass* 69% 13% 10% 6% 2% 31% 16% 50% 2% 1% 0% 10% 20% 30% 40% 50% 60% 70% 80% Drove Alone Carpool Bus Walk Bike Employer Provided Bus Pass Mode Share No Employer Provided Pass Employer Provided Bus Pass (partial or full cost) 4. Estimate based on Bureau of Economic Analysis data 5. 2012 5-yr ACS, Worker Population by Workplace Geography 75% 13% 8% 2% 2% 53% 7% 39% 2% 0% 0% 10% 20% 30% 40% 50% 60% 70% 80% Drove Alone Carpool Bus Walk Bike Mode Share by Parking Type Free Parking Paid Parking *2014 winter data 33% 6% 56% 14% 0% 22% 5% 68% 7% 2% 0% 10% 20% 30% 40% 50% 60% 70% 80% Drove Alone Carpool Walk Personal Bike WE-cycle Transit Access Mode Share "First Mile" "Last Mile" 7% 9% 6% 7% 1% 1% 3% 1% 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% Commute Personal Work Related All Summer Bicycle Mode Share by Trip Purpose Personal Bike WE-Cycle 17 P224II. RFTA 2014 Regional Travel Patterns Update4 RFTA 2014 Regional Travel Patterns Update 1 SNOWMASS VILLAGE Travel Patterns Community Profile SNOWMASS VILLAGE Travel Patterns Community Profile Snowmass Village Region 2012 Population1 2,766 82,227 Population residing year-round 78%94% Lived in region > 1 year 81%93% Households with children under 16 12%31% Households receiving housing assistance 46%12% Median annual household income $59,000 $66,000 HOUSING/DEMOGRAPHIC DATA O V E R V I E W O T H E R T R I P S ABOUT THE PROJECT SNOWMASS VILLAGE PITKIN B ru shC ree kOwlCree kSnowmassCreekM aroonCreekSpring C ree kWoodyCr e e k W illo w C r eekWildcat CreekSalutationCa n al R oa r i ng ForkRiver H unterC reek WestWil lowCreek OWL CREEK RD BRUS H C R E E K R D 0 1 Miles ¬«82 32% 10% 29% 29% 0% 56% 14% 8% 19% 4% 0% 10% 20% 30% 40% 50% 60% Drove Alone Carpool Bus Walk Bike Winter Personal Trips Mode Share of Residents Snowmass Village Region Winter Resident Personal Trips Mode Share Winter Employee Work-Related Trips Mode Share 36% 21% 13% 15% 14% 41% 23% 9% 18% 9% 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% Drove Alone Carpool Bus Walk Bike Summer Personal Trips Mode Share of Residents Snowmass Village Region Summer Resident Personal Trips Mode Share Summer Employee Work-Related Trips Mode Share PERSONAL TRIPS OF RESIDENTS WORK-RELATED TRIPS OF WORKERS 58% 34% 4% 2% 2% 64% 17% 8% 9% 3% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Winter Work-Related Mode Share of Employees Snowmass Village Region Note: Small sample size for Snowmass Village summer resident personal trips The Roaring Fork Transportation Authority (RFTA) conducted a regional travel patterns study in 2014 of the Colorado River Valley and Roaring Fork Valley from Parachute to Aspen. Previous studies were completed in 1998 and 2004. The project was a cooperative effort of RFTA, Colorado DOT, and area counties and municipalities. The project was conducted to provide local jurisdictions and planning agencies with information on travel demand within the study area. This includes information about current and future needs for motor vehicles, for public transit and for walking and bicycling. Data from the study was also used to develop travel forecasts and will help companies and agencies design commuter support programs to address needed changes in travel choices. The data collection methodology included two rounds of surveys, a winter and summer survey. The winter survey targeted employees and employers within the study area. The summer survey targeted residents. A total of 1,679 surveys of residents and employees were collected (1,352 in the winter and 327 in the summer) and 110 employer surveys were completed. The region was divided into 23 transportation analysis zones (TAZs) and all data will be available at the TAZ level. A comprehensive report of the study’s finding will be available through RFTA in early 2015. 1% 46% 54% 0%10% 20% 30% 40% 50% 60% Carbondale Aspen Snowmass Village Where Snowmass Residents Work Where Snowmass Village residents work 1% 1% 2% 2% 4% 8% 8% 10% 10% 11% 14% 29% 0% 5% 10% 15% 20% 25% 30% 35% Rifle Redstone Area Rural Eagle County Rural East Pitkin County Other Rural Garfield Co. Missouri Heights El Jebel Glenwood Springs Aspen Basalt Carbondale Snowmass Village Where Snowmass workers live Where Snowmass Village workers live C O M M U T I N G Transportation Analysis Zone Map of Snowmass Village COMMUNITY GEOGRAPHY The Snowmass Village community profile includes data collected for the following transportation analysis zone(s) (TAZ) mapped at right: • Snowmass Village The “Region” encompasses all 23 TAZs in the region, in- cluding all of Garfield and Pitkin Counties and the por- tion of Eagle County within the Roaring Fork Valley. All data presented was collected from the 2014 Winter and Summer Roaring Fork Transportation Authority (RFTA) Travel Patterns Survey unless otherwise indicated. 1. U.S. Census Bureau, 2012 American Community Survey (ACS) COMMUTING DATA OF RESIDENTS COMMUTING DATA OF WORKERS Mode share is displayed above for the two trips purposes other than commute trips (shown on page 2 in the “Com- muting” section). These include work-related trips, which are trips made during work by employees for business purposes, and personal trips, which cover all other trips that are not commute or work-related trips. 53% 13% 20% 0% 13% 58% 14% 10% 9% 9% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Summer Work-related Trips Mode Share of Employees Snowmass Village Region Note: Small sample size of employees working in Snowmass Village Note: Small sample size for Snowmass Village summer employee work-related trips 18 P225II. RFTA 2014 Regional Travel Patterns Update2 RFTA 2014 Regional Travel Patterns Update 3 SNOWMASS VILLAGE Travel Patterns Community Profile SNOWMASS VILLAGE Travel Patterns Community Profile % of Residents who . . .Snowmass Village Region Own a bus pass/stored value card 20%27% Live within 5 blocks of a bus stop 78%40% Live over a mile from nearest bus stop 3%34% Have taken VelociRFTA in last 30 days 62%35% Have taken other bus in last 30 days 85%39% TRANSIT DATA VelociRFTA 13% Other Bus 77% Both 10% Bus Used For Typical Commute Bus used for typical commute 33% 45% 50% 52% 71% 45% 59% 62% 60% 49% 0%50%100% Sidewalks are Continuous Crosswalk/Crossings Available Comfortable/Pleasant Safe Environment Bus Stop in Walking Distance Walking in Your Community (Agree or Strongly Agree) Region Snowmass Village % of residents who agree/strongly agree that . . . WALKING IN SNOWMASS VILLAGE % of residents who agree/strongly agree that . . . BICYCLING IN SNOWMASS VILLAGE Snowmass Village Region Vehicle available for commuting 71%86% Average commute distance 6 miles 16 miles Average commute time 19 mins 25 mins Work and live in same community 54%36% Different employer winter/summer 17%8% COMMUTING DATA OF RESIDENTS Snowmass Village Region 2012 Worker population2 1,928 48,385 Employer provided bus pass (part/all)27%18% Workers with free parking at work 87%91% Different employer winter/summer 35%8% COMMUTING DATA OF WORKERS C O M M U T T I N G 71% 6% 6% 6% 11% 52% 15% 17% 9% 8% 0% 10% 20% 30% 40% 50% 60% 70% 80% Drove Alone Carpool Bus Walk Bike Summer Commute Mode Share of Residents Snowmass Village Region Summer Resident Commute Mode Share Summer Employee Commute Mode Share T R A N S I T W A L K / B I K E 12% 19% 23% 33% 33% 35% 22% 16% 25% 25% 27% 44% 0%20% 40% 60% Bus stop is far from work Job requires use of personal vehicle Bus stop is far from home Bus takes too much time Need to make stops durring commute Other factors Barriers to riding the bus Region Snowmass Village Winter Personal Trips Mode Share of Residents Barriers to riding the bus Would ride the bus more frequently if . . . 4% 7% 9% 12% 21% 29% 37% 8% 18% 17% 11% 16% 37% 23% 0%20%40% Increase public education Reduce fares Add new routes Add more bus stops Other changes Would not ride more often Increase service frequency Would ride bus more often if Region Snowmass Village 44% 46% 64% 58% 56% 57% 0% 20% 40% 60% 80% Convenient Safe Easy Access to Paths/Trails Biking in Your Community (Agree or Strongly Agree) Region Snowmass Village 35% 10% 48% 5% 1% 62% 12% 19% 5% 2% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Winter Commute Mode Share of Residents Snowmass Village Region Winter Resident Commute Mode Share 42% 16% 38% 3% 1% 62% 12% 19% 5% 2% 0% 10% 20% 30% 40% 50% 60% 70% Drove Alone Carpool Bus Walk Bike Winter Commute Mode Share of Employees Snowmass Village Region Winter Employee Commute Mode Share 43% 19% 16% 16% 7% 35% 10% 48% 5% 1% 0% 10% 20% 30% 40% 50% 60% Drove Alone Carpool Bus Walk Bike Winter Commute Mode Shift of Residents 2004 2014 Winter Resident Commute Mode Shift Winter Employee Commute Mode Shift 46% 20% 24% 8% 2% 42% 16% 38% 3% 1% 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% Drove Alone Carpool Bus Walk Bike Winter Commute Mode Shift of Employees 2004 2014 *2004 data represents Aspen and Snowmass Village and is from the 2004 Local & Regional Travel Patterns Survey *2004 data represents Aspen and Snowmass Village and is from the 2004 Local & Regional Travel Patterns Survey 2. 2012 5-yr ACS, Worker Population by Workplace Geography 50% 14% 26% 3% 6% 52% 15% 17% 9% 8% 0% 10% 20% 30% 40% 50% 60% Drove Alone Carpool Bus Walk Bike Summer Commute Mode Share of Employees Snowmass Village Region Note: Small sample size for Snowmass Village summer resident commute Note: Small sample size for Snowmass Village winter resident com- mute Note: Small sample size for Snowmass Village summer employee commute 19 P226II.