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File Documents.520 N 8th St.0032.2017 (11).ARBK
DRAINAGE REPORT FOR 520 NORTH 8TH STREET CITY OF ASPEN, COLORADO PARCEL ID: 2735-121-14-003 PREPARED FOR: Jamie Tisch PO Box 1470 Aspen, CO 81612 PREPARED BY: High Country Engineering, Inc. 1517 Blake Avenue, Suite 101 Glenwood Springs, CO 81601 (970) 945-8676 March 10th, 2017 Revised: June 19th, 2017 HCE JOB NUMBER: 2161819.01 10/09/2017 Page 2 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc TABLE OF CONTENTS SECTION PAGE I. GENERAL LOCATION AND DESCRIPTION OF SITE 4 II. DRAINAGE STUDIES 5 III. EXISTING SUB BASIN DESCRIPTION 6 IV. DRAINAGE DESIGN CRITERIA 7 V. DRAINAGE FACILITY DESIGN 9 VI. CONCLUSION 13 VIII. REFERENCES 14 EXHIBITS: 1. Vicinity Map (8.5”x11”) 2. Drainage Flow (8.5”x11”) 3. Soils Reports (HP-Kumar Geotech) 4. Existing Drainage Conditions (11”x17”) 5. Proposed Drainage Conditions (11”x17”) 6. Tree Canopy Credit (11”x17”) 7. FEMA Mapping (11”x17”) 8. USDA Web Soil Survey (8.5”x11”) Appendices Hydrologic Computations Existing Conditions Proposed Conditions Hydraulic Computations Swale Calculations Pipe Calculations Drywell WQCV Inlet Capacity Calculations Aspen Charts and Figures 10/09/2017 Page 3 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc Engineers Certification “I hereby affirm that this report and the accompanying plans for the construction of residences, driveway, patios and general site improvements at 440 Riverside Avenue, Aspen, CO was prepared by me (or under my direct supervision) for the owners thereof in accordance with the provisions of the City of Aspen Urban Runoff Management Plan and approved variances are exceptions listed thereto. I understand that it is the policy of the City of Aspen that the City of Aspen does not and will not assume liability for drainage facilities designed by others.” License No. 29975 Roger D. Neal, P.E. Licensed Professional Engineer, State of Colorado 10/09/2017 Page 4 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc I. GENERAL LOCATION AND DESCRIPTION OF SITE A. Location Lots A and B of the Charles and Helga Marqusee Parcel, also known as 520 North 8th Street, is located in the Castle Creek Drainage Basin. The property is directly 800 feet east of Castle Creek and 2,000 feet south of the Roaring Fork River, approximately. North 8th Street is on the north side of Highway 82 and runs for approximately 1,200 feet to the north of the highway alignment. The site is located within the City of Aspen, County of Pitkin, State of Colorado. A Vicinity Map has been included as Exhibit #1. B. Description of Property The proposed site is approximately 13,256 square feet (0.304 acres) in size per the existing conditions survey. The north and east property lines adjoin Lot 2 Anthony/Marqusee parcel and Lot C of Block 8, respectively. The west and south property lines run parallel to North 8th Street and West North Street. The north and east sides of the proposed site planning are bound by residences, and the south and west sides are bound by roadways. The existing parcel consists of an existing house, driveway with retaining walls, patio, walkway, vegetation, utility pedestals and existing fencing. There are multiple trees on the site per the existing conditions survey. These existing trees are noted on the existing conditions survey and a tree removal permit from the architect/owner. The remaining trees on the site will be protected from the proposed construction activities per the City Foresters recommendations during construction. The storm water on the existing site flows from southwest areas to the northeast. Western and southern flows enter the site from the east lane of North 8th Street and the driveway west of the property line. Most of these flows discharge into the existing ditch or sheet flow of the property to the northeast. Runoff north of the driveway and residence flows off site to the northeast. Stormwater south of the driveway and residence flows into the existing irrigation ditch. Design points show the location of historic runoff released from the site, but the flows convey offsite as sheet flow, thus the points are for flow volume information only. There are no point sources of release. This site is located on the boundary of the Castle Creek and Aspen Mountain drainage basins; therefore, no significant offsite basins were used in the design. Because of the crowned pavement of North 8th Street, a small amount of runoff comes from the east lane, as shown in the existing basin map. The historic drainage of the site was delineated into two basins, one offsite and one onsite, see attached existing basin map for site layout (Exhibit #3). C. Lot Soils Description A site-specific geotechnical soil study was completed by H-P/Kumar, Inc. on February 10th, 2017, project number 17-7-157. The geotechnical study describes the site as having about 3 feet of organic sandy clay and silt with gravel fill overlying dense, silty gravel and sand with cobbles and boulders. There was no free water encountered in the boring at the time of excavation, and the subsoils were moist to slightly moist with depth. This type of soil would 10/09/2017 Page 5 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc be classified as Type B soils, well-draining. A percolation test was performed in the completed 4-inch diameter borehole at the approximate proposed drywell location. A percolation rate of 4-8 minutes per inch was obtained by the test and the drywell should be suitable for surface water disposal at the site. The site is also well above the river elevation and groundwater in not anticipated at the depth of our drywell. Groundwater was not encountered to the borehole depth of 12 feet. The City of Aspen soils map locates this site in the Type “B” soils area. According to the USDA Web Soil Survey, the property is within section 107 and the report states that it consists of soil Type “B”; see USDA Web Soil Survey exhibit. D. Description of Project Goals The proposed project will consist of re-grading select areas of disturbance resulting from the removal or replacement of impervious areas, as well as a house remodel. A large amount of the construction will be the remodel of the existing home. There will also be an existing patio, concrete walkway, and retaining wall removed from the site. A proposed smaller patio replaces the one removed from the area north of the home. The disturbed area around the home receives revegetation with native grasses and sod per the landscaping plans. The site is located in the Castle Creek Basin; therefore, the property owner will not be able to pay the fee-in-lieu of detention. The onsite inlet, trench drain and roof outlet will be collected and transferred to a drywell partially located in the north part of the driveway. This drywell will collect the required WQCV per the city code at a factor of 1.5 times the required volume, as well as the remaining volume for detention. The site is required to capture 67.3CF of WQCV, thus sizing the drywell to capture 100.9CF of volume due to the factor of safety. The calculated WQCV utilized the tree canopy credit for effective impervious area per the URMP. The site has been broken up into four onsite proposed basins, see attached proposed basin map for site layout (Exhibit #4). II. DRAINAGE STUDIES A. Major Basin Description The proposed site is located on FEMA’s Flood Insurance Rate Map (FIRM) No. 08097C0203C which has an effective date of June 4, 1987. The site is located in Zone-X, this zone is described as areas determined to be outside 100-year and 500-year floodplains. The 100 year floodway line follows the Roaring Fork River to the west of the site per the survey documents and FEMA mapping. There are no major drainage ways, facilities, or easements within the property boundary. The existing site is outside the affected areas per the WRC Engineering mapping and report for 100yr and mudflow events. The Mud Flow Zone mapping in the Storm Drainage Master Plan for the City of Aspen, Colorado by WRC Engineering, Inc. in November of 2001 was utilized for this section. Other residential areas surround the property. 10/09/2017 Page 6 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc B. Previous Drainage Studies There are no previous site specific drainage studies for the site. The proposed site is located within the Study Area Boundary for the “Storm Drainage Plan for the City of Aspen” by WRC Engineering, Inc. in November 2001; however, the site does not drain to the storm sewer system for the City of Aspen. C. Receiving System and Effects of Adjacent Drainage Issues There are no major drainage issues with the adjacent properties that affect the site or that the site affects. The existing site north and east of the residence discharges sheet flow to the north and east property lines as it did historically. The area southwest of the existing site discharges to an existing irrigation ditch then travels north and parallel to Meadows Road towards the Aspen institute. The area southeast of the site discharges a small amount of sheet flow to the east property line. This system ultimately delivers the stormwater to the Roaring Fork River. III. EXISTING SUB BASINS DESCRIPTION The existing site’s historic drainage patterns flow from the west to the northeast. As stated above, Castle Creek and the Roaring Fork River are the direct receiving facilities. The difference in the historic conditions versus the proposed conditions with historic condition flowrates will determine the amount of storm water allowed to flow offsite. The historic site has been broken into one onsite drainage basin and one offsite. Refer to sheet EXDR (exhibit #4) for a map of existing basin layouts. Basin EX-1 encompasses the entire lot. Basin EX-2 encompasses an area to the west of the lot. Historic Flow Path One: Runoff from basin EX-1 sheet flows to the northeast across the site from a high point in the southwest portion of the lot. The runoff continues to sheet flow past the property boundary onto the adjacent lot before crossing Meadows Road. Once north of Meadows Road, the flow continues to travel north between two residences into a large, open field primarily covered with sagebrush and native grasses. After flowing across this field, the stormwater runoff enters the Roaring Fork River. Please see exhibit 2. The only potentially affected property would be the lot just north of the site; however, the location of the properties in the Castle Creek drainage basin prevents excessive runoff from other offsite locations. The basin consists of natural/historic grasses and plants. Design point one has been associated with the northeast corner of the lot. Calculations for onsite flows pertain to this location. 10/09/2017 Page 7 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc Table 1. Existing Basin Characteristics BASIN AREA, ACRES C, 10YR I, 10YR Q10-YEAR, CFS C, 100YR I, 100 YR Q100-YEAR, CFS EX-1 0.3 0.15 2.38 0.11 0.35 3.81 0.41 EXOS-1 0.033 0.15 2.46 0.01 0.35 3.93 0.01 TOTAL 0.12 TOTAL 0.42 Existing historic release rates from the site release at Design Point 1-2 are at a rate of 0.12cfs (10yr) and 0.42cfs (100yr). IV. DRAINAGE DESIGN CRITERIA A. Criteria This drainage study was prepared in conformance with the City of Aspen, Colorado Urban Runoff Management Plan (URMP), dated April of 2010 and the revised sections dated thereafter (September 2014). More than 1,000 square feet of area will be disturbed with the proposed construction; therefore, the site is viewed as a Major Drainage Report per the URMP. More than 25-percent of the site is being disturbed, so water quality for the entire site will be necessary per the URMP. The existing site was analyzed in its historic condition (i.e. no improvements). The offsite basin consisting of landscape area was analyzed as existing (open space) per the URMP. Water Quality Capture Volume (WQCV) will be determined for the site as per the URMP standards. The WQCV is defined as the treatment for up to the 80th percentile runoff event, corresponding to between a 6-month to 1-year event. The WQCV was determined using the equations and Figure 8.13 from Chapter 8 of the URMP. WQCV was calculated using the effective imperviousness from the tree canopy credit. The WQCV equation is: Volume (ft3)=WQCV in watershed inches x 1 ft/12 in x area (acres) x 43,560 ft2/acre. B. Hydrologic Criteria The hydrologic methods for this study are outlined in the URMP from the City of Aspen, Colorado (April, 2010) and updates utilizing a Microsoft Excel spreadsheet set up for the Rational Method calculations/equations. The obtained rainfall amounts for each basin used the updated Figure 2.1 “IDF Curves for Aspen, Colorado” in the URMP publication from the City of Aspen, Colorado. Using these curves, the rainfall intensity corresponding to the 2-yr, 1-hr storm 10-yr, 1-hr storm, and 100- yr, 1-hr storm event were determined based on the time of concentration for each basin. Figure 3.2 from the URMP was used to determine the runoff coefficients for the 2-year, 10- year and 100-year storm events since the soils were determined to be Type ‘B’ soils. The Rational Method was used for historic and proposed flowrates as outlined in the URMP calculations/equations. The proposed WQ underground structure was sized using the URMP methodology and the required detention for the entire tributary area of the site. The required 10/09/2017 Page 8 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc detention was determined using the methodology described in the URMP for a drywell without a controlled outlet. WQCV and required detention volumes will be captured in the underground drywell and percolate into the silty sandy gravel/cobble underneath and around the drywell. The drywell has been designed to accommodate a total of 549.4CF of detention, including an upper chamber capable of 113.1CF. The drywell meets the total required detention of 514CF, including 100.9CF of WQCV per the 1.5 factor calculated against the overall site requirements. The drywell will gather storm water from the underground downspout, a 6” inlet along the north patio and the trench drain near the garage within the driveway. This water conveys to the drywell via 6” PVC piping at a slope of 2% per the design documents. The proposed drywell detention will drain into the surrounding soil within the 24-hour requirement. The drywell has a proposed percolation area of 349SF that exceeds the required 259SF. If the drywell surpasses the proposed detention and WQCV, the system will allow water to back up out the trench drain grate and overflow north of the driveway to sheet flow across the site, as it did historically. The trench drain will act as a release structure for the 10y rand 100yr storm event. The 14FT trench drain grate helps disperse the overflow to alleviate concentrated discharge. All charts and figures mentioned from the URMP are located in the last section of the appendices under the “Aspen Charts/Figures” section. C. Hydraulic Criteria The pipes within the system have also been calculated utilizing the Hydrology pipe calculator with AutoCAD’s system. All pipes have the ability to carry their split basin design flows anticipated to hit each section of pipe runs. See basin descriptions below for explanation. D. Site Constraints The site is mainly clear of any onsite issues, but has disturbance areas within tree driplines. The site is vegetated with native grasses and brush. E. Easements, Irrigation Facilities, Waterways There are no major drainage easements or tracts located on the site. There are standard zoning setbacks from property lines. These setbacks do not affect the overall site drainage design. 10/09/2017 Page 9 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc V. DRAINAGE FACILITY DESIGN. A. General Concept The proposed site plan calls for all a proposed single family home to be remodeled and replacement of the driveway. A patio north of the existing home will be removed and replaced with a smaller concrete patio attached to the north end of the residence. A proposed gravel patio will be constructed just south of the residence. A drywell will also be constructed underneath a removed retention wall to allow for the capture of the required WQCV and detention per the URMP code. The remaining area on the parcel outside of the hardscape will remain undisturbed. Please see landscaping plans for specific hardscape materials and planting details. The only change to the stormwater released from the site will be that less runoff will sheet flow onto the northeast neighboring property. This will improve the neighboring properties stormwater situation. Historically, a total rate of 0.46cfs left the site as sheet flow to the northeast. In the proposed condition, only a total of 0.23cfs will sheet flow to the northeast. The storm water facilities designed within this report focuses on collection and distribution to the drywell system. Due to site constraints, this is the most feasible design for the 13,256SF lot. Piping collection systems will allow for capture of all hardscape water and the transfer of that water to a drywell with the WQCV and required detention on the site. The infiltration drywell size holds the WQCV based on the 1.5 factor and the detention required for drywells per code. The site-specific soil study determined a percolation rate of 4-8 min/inch for the approximate proposed drywell location. As stated above, this drywell will drain within the required 24 hours. The 9 Principles for storm water quality management were followed during the design process to create the best storm water design and water quality management for this particular site and design concept. Principle No. 1: From day one of all projects that HCE is reviewing we are always pushing storm water, detention and WQ structures on the architects and landscape planners. In this case we have a limited space for these features due to the preservation of existing structures/landscape and the prevention of disturbed areas near the numerous trees that encompass the house. The site has the spacing between the replaced driveway and tree driplines to allow for a 4’ drywell and 7’ of gravel to be installed at the location of the proposed removal of the north retaining wall, thus this was the most appropriate location for the drainage design. Principle No. 2: The proposed redevelopment allows a vast majority of runoff from onsite, impervious areas to be directed to the stormwater quality treatment system. Pervious terrain and tree canopies cover or surround the remaining areas. The main structure has been built north of the driveway and allows less water to run off site than historical conditions. Less water passes into the neighboring property to the north and the irrigation ditch along the west property line. 10/09/2017 Page 10 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc Principle No. 3: The proposed changes to the site will reduce impervious area on the property. Principle No. 4: The proposed removal of various impervious areas within the PR-2 basin reduces runoff rates. The increased contact between stormwater and the adequately sloped soil will support infiltration and prevent ponding, thus reducing runoff volume. Disturbance within tree driplines will be avoided as much as possible. The proposed redevelopment will more closely match natural conditions than the existing features onsite. Principle No. 5: The drywell being oversized will reduce small storm runoff from the site and will accommodate for 10yr or 100yr storm events. The drywell capacity includes the required WQCV. Principle No. 6: The stormwater facilities on this site take great care to direct water away from the neighboring property and to appropriate facilities, resulting in reduced flow leaving the site. This will improve the impact of stormwater on neighboring properties. Principle No. 7: The treatment train for this site is limited, but invisible to the public in nature. The addition of stormwater back into the ground in a fast method, such as a drywell, adds to the WQ process for the stormwater and recharges the area’s aquafers in a faster manner that just stormwater runoff itself. Principle No. 8: All of the onsite facilitates are easily accessed for cleaning and inspection. The drywell will have a 24” removable grate for easy access and cleaning in the event that the system fails and needs repair. The inlet and trench drain will have removable grates that act as cleanouts for onsite piping at appropriate locations, outside of the actual downspout/inlet collection locations themselves. Principle No. 9: There are no steep or deep channels being proposed that could cause tripping or fall hazards. All methods of actual treatment and storage are out of the public’s site and allow safe passage. The proposed site has been separated into four proposed onsite drainage basins and two offsite drainage basins. Refer to sheet PRDR, Exhibit #5, in the exhibit section for a map of the proposed basins and drainage design. Basin PR-1 consists of all impervious areas on the site; roof, hardscape patios and driveway. The drainage from PR-1 is routed to the drywell through the piping system and then overtops the driveway trench drain as a release structure. The flows release at design point 1. Basin PR-2 consists of the yard areas between the home and neighboring residential properties. This area will be primarily undisturbed, except for the removal of an existing patio to be replaced by grasses, thus preserving the historic nature of the basin. The basins overall design flows are show at design point 2. Basin PR-3 consists of a flagstone path, grass area and irrigation ditch along the west property 10/09/2017 Page 11 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc line. The proposed basin is just south of the driveway and east of the home and will release to the existing irrigation ditch. This basin will remain undisturbed and is almost completely covered by coniferous tree canopies. The flows release at design point 3. Basin PR-4 consists of the yard area just south of the home and north of West North Street, as well as an existing flagstone patio. This area will remain undisturbed grass or native vegetation. Tree canopy nearly covers the entire basin. Design point 4 shows the basin’s overall design flows. The design for proposed conditions on the site satisfies WQCV and the stormwater detention requirements. Table 2, is a summary of the proposed basins. Table 2. Proposed Basin Characteristics BASIN AREA, ACRES C, 10YR I, 10YR Q10-YEAR, CFS C, 100YR I, 100 YR Q100-YEAR, CFS PR-1 0.119 0.87 3.96 0.41 0.91 6.33 0.69 PR-2 0.131 0.15 2.40 0.05 0.35 2.40 0.18 PR-3 0.031 0.18 2.92 0.02 0.38 2.92 0.06 PR-4 0.023 0.23 2.37 0.01 0.41 2.37 0.04 OS-1 .015 0.92 3.96 .05 0.95 3.96 0.09 ONSITE TOTAL 0.54 ONSITE TOTAL 1.06 B. Low Impact Site Design The proposed site design incorporates as much low impact site design criteria from the URMP as is site feasible. Roof downspouts, patio inlets and the driveway trench drain will drain to a proposed pipe system that will transfer the proposed flows to the designed drywell system north of the driveway. All storm water produced by the home and patio will be conveyed through the infiltration system, thus reducing the transfer of pollutants to the City of Aspen storm sewer system and the Roaring Fork River release point. The infiltration gallery will also directly add water to the ground water within the Aspen area. C. Specific Details The composite impervious percentage proposed for each basin can be located in Table 3, below. The effective imperviousness from tree canopy credit and corresponding WQCV can be seen in table 4, below. The effective imperviousness was then used to determine the WQCV in watershed inches on Figure 8.13. Tree canopy credit was calculated using the coniferous and deciduous areas within the property lines. Tree canopy areas that overlapped were not calculated more than once, and the tree with the larger dripline diameter was used to determine whether deciduous or coniferous canopies were used. Please see exhibit 6 for tree canopy credit calculations. The system being utilized for the WQCV is capable of capturing the 67.3CF plus a scaled factor of 1.5 to a final required drywell volume of 100.9CF of volume. The drywell will detain all required storage, including WQCV. Table 3 a. Proposed Impervious Areas Table 10/09/2017 Page 12 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc BASIN AREA (S.F.) IMPERVIOUS AREA (SF) PERCENT IMPERVIOUS PR-1 5,187 5,016 96.7% PR-2 5,707 45 0.8% PR-3 1,342 78 5.8% PR-4 996 121 12.1% TOTAL 13,232 5,260 39.7% Table 3. Tree Canopy Credit and Proposed WQCV TREE CANOPY CREDIT TREE TYPE CANOPY AREA (SF) CONIFEROUS 2,503.0 DECIDUOUS 3,640.0 IMPERVIOUSNESS SITE TOTAL AREA 5,260 EFFECTIVE AREA 3,963 EFFECTIVE (%) 29.9% WQCV (watershed-inches) 0.065 Volume (CF) 67.3 D. Operation and Maintenance The drywell will need to be inspected and cleared of rubbish and debris quarterly to make sure that the filter/riser pipe has not become clogged and is functioning properly. The top three inches of the lower chamber infiltration media shall be scarified yearly or more frequently to obtain optimum infiltration of surface runoff. If water is pooling, then the filter material may need to be scarified more frequently. If the filter material continues to fail, then the top six inches of the material should be removed and replaced with sand. This may occur every two to five years. The overflow grate must also be inspected to make sure it has not clogged. Review of the overflow structure/trench drain piping and trench system should occur at least every 6 months or after large storm events. The proposed area/patio inlet shall be inspected and cleared of rubbish and debris quarterly as well as after large storm events. 10/09/2017 Page 13 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc The drains shall be inspected after large storm events to insure proper function. If standing water is observed within the area inlet, then the grate shall be removed and the drain shall be jetted clear. The owners or owner’s representative will be responsible for the maintenance and upkeep of the drainage facilities. The property owner shall dispose of sediment and any other waste material removed from a reservoir at a suitable disposal site and in compliance with local, state, and federal waste regulations. VI. CONCLUSION A. Compliance with Standards This drainage report has been prepared in accordance with City of Aspen Regulations. The proposed storm water facilities will capture the WQCV and required detention. B. Drainage Concept The proposed drainage design will be effective in controlling any adverse downstream impacts on landowners or structures by having the storm water leave the site directed toward City stormwater systems instead of uncontrolled drainage ways as historically exist. Water quality issues will not be a concern as the runoff carrying pollutants is being captured and stored in the proposed drywell structure. 10/09/2017 Page 14 j:/sdskproj/216/1046/word/drainage/drainage report 440 Riverside.doc VII. References City of Aspen, Colorado: Design and Construction Standards, June 2005. City of Aspen, Colorado: Urban Runoff Management Plan. April 2010, Sept 2014 Update. WRC Engineering, Inc. “Storm Drainage Master Plan for the City of Aspen, Colorado”. November 2001. HP Geotech, Inc. “Subsoil Study for Existing Grade Conditions and Building Foundation Design, Proposed Residence, Lot 2, Anderson Subdivision, 400 Riverside Avenue, Aspen, CO” dated November 13, 2105, Job Number 115 502A. UDFCD. www.udfcd.org. 10/09/2017 EXHIBITS 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 10/09/2017 I P1-10yr P1-100yr TdEX-1 2.38 0.77 14.3EX-1 3.81 1.23 14.3I P1-10yr P1-100yr TdEXOS-1 2.46 0.77 13.6EXOS-1 3.93 1.23 13.6Rainfall Intenstity Chart EX-1Rainfall Intenstity Chart EXOS-2REACHTcTCTc10 YEAR100 YEAREXOS-10.0813.60.027714.3EX-11189310.7MINIMUM 5 MINUTES14.3OVERLAND FLOW 0.0227LAND SLOPE, S (ft./ft.)SURFACE DESCRIPTION 0(MIN)13.63.81EX-12.385.01RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.08BASIN0.0FLOW LENGTH, L (TOTAL <300 FT.) (ft.)AREA IDENTIFIER3.93EXOS-10.00001To (MIN)2.460.010.55.0TRAVEL TIME FLOW SLOPE, S (ft./ft.)0.00000FLOW LENGTH, L (ft.)TRAVEL TIME = L/(60V) (min.)FLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)URBAN CHECK = 10+L/180EX-113,256.00.3040.00.00.080.150.35EXOS-21,432.00.0330.00.00.080.150.35TOTAL SITE 14,688.00.3370.00.00.080.150.35Type B Soils 5 YR RUNOFF COEFFICIENT10 YR RUNOFF COEFFICIENT100 YR RUNOFF COEFFICIENTPERCENT IMPERVIOUSBASIN AREA (S.F.) AREA (ACRE) IMPERVIOUS AREA (SF)10/09/2017 REACHTcTCTc2 YEAR INTENSITY10 YEAR INTENSITY100 YEAR INTENSITYPR-41.452.373.790.009210.014.410.45.0PR-40.15065.00.0114.40.00.035.010.024.00.014.14.00.014.1(MIN)TRAVEL TIME = L/(60V) (min.)URBAN CHECK = 10+L/1800.0PR-20.0210.60.080119.0To (MIN)PR-1111.3RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.840AREA IDENTIFIERFLOW SLOPE, S (ft./ft.)BASINMINIMUM 5 MINUTES6.33PR-13.962.42OVERLAND FLOW FLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)FLOW LENGTH, L (ft.)TRAVEL TIME SURFACE DESCRIPTIONFLOW LENGTH, L (TOTAL <300 FT.) (ft.)LAND SLOPE, S (ft./ft.)0.010.75.00.0312.92PR-31.47 1.784.673.84PR-22.405.0PR-30.10033.80.01210.00.00.0120.010.010.215OS-10.9032.890.0141.90OS-12.423.966.330.014101.910.2SITE TOTAL5,260 EFFECTIVE3,963 EFFECTIVE (%)29.9%IMPERVIOUSNESS AREA (SF)PR-15,187.00.1195016.096.7%0.830.840.870.91PR-25,707.70.13145.30.8%0.020.080.150.35PR-31,342.00.03178.05.8%0.040.100.180.38PR-4996.00.023120.512.1%0.070.150.230.41OS-1656.00.015656.0100.0%0.890.900.920.95 Onsite Only 13,232.7 0.3045259.839.7%29.9%0.06167.30.230.300.360.49Time 1.5 for Drywell 100.9100 YR RUNOFF COEFFICIENTWQCV (Watershed inches) WQCV (CF)Type B Soils BASIN AREA (S.F.) AREA (ACRE)IMPERVIOUS AREA (SF)PERCENT IMPERVIOUS2 YR RUNOFF COEFFICIENT10 YR RUNOFF COEFFICIENT5 YR RUNOFF COEFFICIENTEFFECTIVE IMPERVIOUS (%)CONIFEROUS2,503.0 0.3DECIDUOUS3,640.0 0.15TREE TYPECANOPY AREA (SF) COEFFICIENTTREE CANOPY CREDITBasin I P1-2yr P1-10yr P1-100yr TdPR-1 2.42 0.47 5.0PR-1 3.960.775.0PR-1 6.331.23 5.0Basin I P1-2yr P1-10yr P1-100yr TdPR-2 1.47 0.4714.1PR-2 2.400.7714.1PR-2 3.841.23 14.1Basin I P1-2yr P1-10yr P1-100yr TdPR-3 1.78 0.4710.0PR-3 2.920.7710.0PR-3 4.671.23 10.0Basin I P1-2yr P1-10yr P1-100yr TdPR-4 1.45 0.4714.4PR-4 2.370.7714.4PR-4 3.791.23 14.4Basin I P1-2yr P1-10yr P1-100yr TdOS-1 2.42 0.475.0OS-1 3.960.775.0OS-1 6.331.23 5.0Rainfall Intenstity Chart PR-3Rainfall Intenstity Chart PR-4Rainfall Intenstity Chart PR-1Rainfall Intenstity Chart PR-2Rainfall Intenstity Chart OS-110/09/2017 10/09/2017 10/09/2017 Hydrologic Soil Group—Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (520 N. 8th Street, Aspen CO) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/2/2017 Page 1 of 4434021543402234340231434023943402474340255434026343402714340279434021543402234340231434023943402474340255434026343402714340279341877341885341893341901341909341917341925 341877 341885 341893 341901 341909 341917 39° 11' 50'' N 106° 49' 52'' W39° 11' 50'' N106° 49' 49'' W39° 11' 48'' N 106° 49' 52'' W39° 11' 48'' N 106° 49' 49'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 15 30 60 90 Feet 0 4 9 18 27 Meters Map Scale: 1:323 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. 10/09/2017 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Survey Area Data: Version 7, Sep 22, 2014 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 12, 2011—Sep 22, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (520 N. 8th Street, Aspen CO) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/2/2017 Page 2 of 4 10/09/2017 Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (CO655) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 107 Uracca, moist-Mergel complex, 1 to 6 percent slopes, extremely s B 0.4 100.0% Totals for Area of Interest 0.4 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties 520 N. 8th Street, Aspen CO Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/2/2017 Page 3 of 4 10/09/2017 Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties 107—Uracca, moist-Mergel complex, 1 to 6 percent slopes, extremely s Map Unit Setting National map unit symbol: jq4g Elevation: 6,800 to 8,400 feet Mean annual precipitation: 16 to 19 inches Mean annual air temperature: 40 to 43 degrees F Frost-free period: 75 to 95 days Farmland classification: Not prime farmland Map Unit Composition Uracca, moist, and similar soils: 50 percent Mergel and similar soils: 40 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Uracca, Moist Setting Landform: Structural benches, valley sides, alluvial fans Down-slope shape: Linear Across-slope shape: Linear Parent material: Mixed alluvium derived from igneous and metamorphic rock Typical profile H1 - 0 to 8 inches: cobbly sandy loam H2 - 8 to 15 inches: very cobbly sandy clay loam H3 - 15 to 60 inches: extremely cobbly loamy sand Properties and qualities Slope: 1 to 6 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Very low (about 2.6 inches) Interpretive groups Land capability classification (irrigated): 6s Land capability classification (nonirrigated): 6s Hydrologic Soil Group: B Ecological site: Stony Loam (R048AY237CO) Map Unit Description: Uracca, moist-Mergel complex, 1 to 6 percent slopes, extremely s--- Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/9/2017 Page 1 of 2 10/09/2017 Other vegetative classification: Stony Loam (null_82) Hydric soil rating: No Description of Mergel Setting Landform: Structural benches, valley sides, alluvial fans Down-slope shape: Linear Across-slope shape: Linear Parent material: Glacial outwash Typical profile H1 - 0 to 8 inches: cobbly loam H2 - 8 to 20 inches: very cobbly sandy loam H3 - 20 to 60 inches: extremely stony sandy loam Properties and qualities Slope: 1 to 6 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 6.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Low (about 3.3 inches) Interpretive groups Land capability classification (irrigated): 4s Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Ecological site: Stony Loam (R048AY237CO) Other vegetative classification: Stony Loam (null_82) Hydric soil rating: No Data Source Information Soil Survey Area: Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Survey Area Data: Version 7, Sep 22, 2014 Map Unit Description: Uracca, moist-Mergel complex, 1 to 6 percent slopes, extremely s--- Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/9/2017 Page 2 of 2 10/09/2017 HYDROLOGIC COMPUTATIONS 10/09/2017 EXISTING CONDITIONS 10/09/2017 520 N 8th Street, AspenDRAINAGE REPORTBY: BDBCHECKED BY: RDNDATE: 3-10-17EX-1 13,256.0 0.304 0.0 0.0 0.08 0.15 0.35EXOS-2 1,432.0 0.033 0.0 0.0 0.08 0.15 0.35TOTAL SITE 14,688.0 0.337 0.0 0.0 0.08 0.15 0.35Type B Soils 5 YR RUNOFF COEFFICIENT10 YR RUNOFF COEFFICIENT100 YR RUNOFF COEFFICIENTPERCENT IMPERVIOUSBASIN AREA (S.F.) AREA (ACRE) IMPERVIOUS AREA (SF)10/09/2017 520 N 8th Street, AspenDRAINAGE REPORTBY: BDBCHECKED BY: RDN6/16/2016REACHI P1-10yr P1-100yr TdEX-1 2.38 0.77 14.3EX-1 3.81 1.23 14.3I P1-10yr P1-100yr TdTcEXOS-1 2.46 0.77 13.6TCEXOS-1 3.93 1.23 13.6Tc10 YEAR100 YEARTo = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management PlanTc=To+TtINTENSITY I=29p/((10+T)^0.789) EQUATION 2-1P TAKEN FROM TABLES 2.2 AND 2.3Rainfall Intenstity Chart EX-1Rainfall Intenstity Chart EXOS-2EXOS-10.0813.60.027714.3EX-1118 9310.7MINIMUM 5 MINUTES14.3OVERLAND FLOW0.0227LAND SLOPE, S (ft./ft.)SURFACE DESCRIPTION 0(MIN)13.63.81EX-12.385.01RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.08BASIN0.0FLOW LENGTH, L (TOTAL <300 FT.) (ft.)AREA IDENTIFIER3.93EXOS-10.00001To (MIN)2.460.010.55.0TRAVEL TIMEFLOW SLOPE, S (ft./ft.) 0.00000FLOW LENGTH, L (ft.)TRAVEL TIME = L/(60V) (min.)FLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)URBAN CHECK = 10+L/18010/09/2017 CALCULATED BY: BDBSTANDARD FORM SF-3DATE 3/10/2017STORM DRAINAGE SYSTEM DESIGNCHECKED BY: RDN(RATIONAL METHOD PROCEDURE)Contributing AreaAREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)CHANNEL FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)DESIGN POINT 1DESIGN POINT 2DESIGN POINTDIRECT RUNOFF0.15 14.31 EX-10.112.38PROJECT: 520 N 8TH STREETJOB NO. 2161819.01PIPEDESIGN STORM: EXISTING 10 YEARTRAVEL TIMEREMARKSCHANNELSTRUCTURE NO.0.0513.6 0.00 2.46 0.012 EXOS-2 0.033 0.15TOTAL RUNOFF0.30410/09/2017 CALCULATED BY: BDBSTANDARD FORM SF-3DATE: STORM DRAINAGE SYSTEM DESIGNCHECKED BY: RDN(RATIONAL METHOD PROCEDURE)Contributing AreaAREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)CHANNEL FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)DESIGN POINT 1DESIGN POINT 2JOB NO. 2161016PROJECT: 520 N 8th StreetDESIGN STORM: EXISTING 100 YEARSTRUCTURE NO.DESIGN POINTDIRECT RUNOFFTOTAL RUNOFF CHANNEL PIPE TRAVEL TIMEREMARKS1 EX-1 0.304 0.35 14.3 0.11 3.81 0.412 EXOS-1 0.033 0.35 13.6 0.01 3.93 0.0510/09/2017 PROPOSED CONDITIONS 10/09/2017 520 N. 8TH STREET, AspenDRAINAGE REPORTBY: BDBCHECKED BY: RDNDATE: 3-10-17PR-1 5,187.0 0.119 5016.0 96.7%0.83 0.84 0.87 0.91PR-2 5,707.7 0.131 45.3 0.8%0.02 0.08 0.15 0.35PR-3 1,342.0 0.031 78.0 5.8%0.04 0.10 0.18 0.38PR-4 996.0 0.023 120.5 12.1%0.07 0.15 0.23 0.41OS-1 656.0 0.015 656.0 100.0%0.89 0.90 0.92 0.95 Onsite Only 13,232.7 0.304 5259.8 39.7% 29.9% 0.061 67.3 0.23 0.30 0.36 0.49Time 1.5 for Drywell 100.9CONIFEROUS2,503.0 0.3DECIDUOUS3,640.0 0.15SITE TOTAL 5,260 EFFECTIVE 3,963 EFFECTIVE (%) 29.9%(watershed-inches)0.061Volume (CF)67.35 YR RUNOFF COEFFICIENTEFFECTIVE IMPERVIOUS (%)WQCVTREE TYPECANOPY AREA (SF) COEFFICIENTIMPERVIOUSNESS AREA (SF)Type B Soils BASIN AREA (S.F.) AREA (ACRE)IMPERVIOUS AREA (SF)PERCENT IMPERVIOUS2 YR RUNOFF COEFFICIENT10 YR RUNOFF COEFFICIENT100 YR RUNOFF COEFFICIENTWQCV (Watershed inches) WQCV (CF)TREE CANOPY CREDIT10/09/2017 520 N 8th Street, AspenDRAINAGE REPORTBY: BDBCHECKED BY: RDN3/10/2017REACHBasin I P1-2yr P1-10yr P1-100yr TdPR-1 2.42 0.47 5.0PR-1 3.96 0.77 5.0PR-1 6.33 1.23 5.0Basin I P1-2yr P1-10yr P1-100yr TdTcPR-2 1.47 0.47 14.1TCPR-2 2.400.7714.1TcPR-2 3.841.23 14.12 YEAR INTENSITYBasin I P1-2yr P1-10yr P1-100yr Td10 YEAR INTENSITY100 YEAR INTENSITYPR-3 1.78 0.4710.0PR-3 2.920.7710.0To = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4PR-3 4.67 1.23 10.0C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management PlanINTENSITY I=29p/((10+T)^0.789) EQUATION 2-1Basin I P1-2yr P1-10yr P1-100yr TdP TAKEN FROM TABLES 2.2 AND 2.3 WITHIN THE URMP*INTENSITIES TAKEN FROM FIGURE 2.1 "IDF CURVES FOR ASPEN, COLORADO" FROM URMPPR-4 1.45 0.47 14.4PR-4 2.37 0.77 14.4PR-4 3.79 1.23 14.4Basin I P1-2yr P1-10yr P1-100yr TdOS-1 2.42 0.47 5.0OS-1 3.96 0.77 5.0OS-1 6.33 1.23 5.0Rainfall Intenstity Chart OS-1OS-12.423.966.330.014101.910.25OS-10.9032.890.0141.90Rainfall Intenstity Chart PR-3Rainfall Intenstity Chart PR-4Rainfall Intenstity Chart PR-1Rainfall Intenstity Chart PR-20.0120.010.010.215.0PR-30.10033.80.01210.00.02.92PR-31.47 1.784.673.84PR-22.400.010.75.00.031OVERLAND FLOWFLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)FLOW LENGTH, L (ft.)TRAVEL TIMESURFACE DESCRIPTIONFLOW LENGTH, L (TOTAL <300 FT.) (ft.)LAND SLOPE, S (ft./ft.)BASINMINIMUM 5 MINUTES6.33PR-13.962.42PR-1111.3RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.840AREA IDENTIFIERFLOW SLOPE, S (ft./ft.)(MIN)TRAVEL TIME = L/(60V) (min.)URBAN CHECK = 10+L/1800.0PR-20.0210.60.080119.0To (MIN)0.035.010.024.00.014.14.00.014.15.0PR-40.15065.00.0114.40.0PR-41.452.373.790.009210.014.410.410/09/2017 CALCULATED BY: BDBSTANDARD FORM SF-3DATE: 3-10-17STORM DRAINAGE SYSTEM DESIGNCHECKED BY: RDN(RATIONAL METHOD PROCEDURE)Contributing AreaAREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)Design Point 3Design Point 44PR-40.023 0.07 14.42 0.002 1.45 0.000.001 1.78 0.003PR-30.031 0.04 10.011.47Design Point 1Design Piont 2PR-2 10.02PR-15.000.1190.131PROJECT: 520 N 8th StreetJOB NO. 2161819.01DIRECT RUNOFF20.24STRUCTURE NO.DESIGN POINTREMARKS0.00DESIGN STORM: PROPOSED 2 YEAR0.8314.13 0.0030.10 2.42TRAVEL TIMEPIPESTREETTOTAL RUNOFF5 OS-1 0.015 0.89 1.88 0.013 2.42 0.03Design Point 110/09/2017 CALCULATED BY: BDBSTANDARD FORM SF-3DATE: 3-10-17STORM DRAINAGE SYSTEM DESIGNCHECKED BY: RDN(RATIONAL METHOD PROCEDURE)Contributing AreaAREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)Design Point 40.005 2.37 0.014PR-40.023 0.23 14.420.02Design Point 3Design Piont 23PR-30.031 0.18 10.01 0.006 2.920.020 2.40 0.052PR-2 0.131 0.15 14.130.41Design Point 1TRAVEL TIMEREMARKS1PR-10.119 0.87 5.00 0.10 3.96JOB NO. 2161819.01PROJECT: 520 N 8th StreetDESIGN STORM: PROPOSED 10 YEARSTRUCTURE NO.DESIGN POINTDIRECT RUNOFFTOTAL RUNOFF STREET PIPE5 OS-1 0.015 0.92 1.88 0.014 3.96 0.05Design Point 110/09/2017 CALCULATED BY: BDBSTANDARD FORM SF-3DATE: 3-10-17STORM DRAINAGE SYSTEM DESIGNCHECKED BY: RDN(RATIONAL METHOD PROCEDURE)Contributing AreaAREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)Design Point 40.009 3.79 0.044PR-40.023 0.41 14.420.06Design Point 3Design Piont 23PR-30.031 0.38 10.01 0.012 4.670.046 3.84 0.182PR-2 0.131 0.35 14.130.69Design Point 1TRAVEL TIMEREMARKS1PR-10.119 0.91 5.00 0.11 6.33JOB NO. 2161819.01PROJECT: 520 N. 8TH STREETDESIGN STORM: PROPOSED 100 YEARSTRUCTURE NO.DESIGN POINTDIRECT RUNOFFTOTAL RUNOFF STREET PIPE5 OS-1 0.015 0.95 5.00 0.014 6.33 0.09Design Point 110/09/2017 HYDRAULIC COMPUTATIONS 10/09/2017 PIPE CALCULATIONS 10/09/2017 4" PVC PIPE FROM AREA INLET FOR 10-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 4.0000 in Flowrate ........................ 0.0300 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 0.7517 in Area ............................ 0.0873 ft2 Wetted Area ..................... 0.0114 ft2 Wetted Perimeter ................ 3.5870 in Perimeter ....................... 12.5664 in Velocity ........................ 2.6400 fps Hydraulic Radius ................ 0.4562 in Percent Full .................... 18.7921 % Full flow Flowrate .............. 0.3888 cfs Full flow velocity .............. 4.4549 fps *PIPE ACCOMMODATES 6.5% OF PR-1 FLOW 10/09/2017 4" PVC PIPE FROM 6" AREA INLET FOR 100-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 4.0000 in Flowrate ........................ 0.0450 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 0.9189 in Area ............................ 0.0873 ft2 Wetted Area ..................... 0.0151 ft2 Wetted Perimeter ................ 3.9989 in Perimeter ....................... 12.5664 in Velocity ........................ 2.9727 fps Hydraulic Radius ................ 0.5451 in Percent Full .................... 22.9730 % Full flow Flowrate .............. 0.3888 cfs Full flow velocity .............. 4.4549 fps *PIPE ACCOMMODATES 6.5% OF PR-1 FLOW 10/09/2017 6" PIPE TO DRYWELL FOR 10-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 6.0000 in Flowrate ........................ 0.4600 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 2.6440 in Area ............................ 0.1963 ft2 Wetted Area ..................... 0.0834 ft2 Wetted Perimeter ................ 8.7110 in Perimeter ....................... 18.8496 in Velocity ........................ 5.5173 fps Hydraulic Radius ................ 1.3783 in Percent Full .................... 44.0661 % Full flow Flowrate .............. 1.1462 cfs Full flow velocity .............. 5.8376 fps Critical Information Critical depth .................. 4.1476 in Critical slope .................. 0.0043 ft/ft Critical velocity ............... 3.1509 fps Critical area ................... 0.1460 ft2 Critical perimeter .............. 11.7199 in Critical hydraulic radius ....... 1.7937 in Critical top width .............. 6.0000 in Specific energy ................. 0.6934 ft Minimum energy .................. 0.5184 ft Froude number ................... 2.3735 Flow condition .................. Supercritical *PIPE RECEIVES FLOW FROM THE SUM OF PR-1 AND OS-1 10/09/2017 6" PVC PIPE TO DRYWELL FOR 100-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 6.0000 in Flowrate ........................ 0.7800 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 3.6304 in Area ............................ 0.1963 ft2 Wetted Area ..................... 0.1242 ft2 Wetted Perimeter ................ 10.6950 in Perimeter ....................... 18.8496 in Velocity ........................ 6.2779 fps Hydraulic Radius ................ 1.6729 in Percent Full .................... 60.5062 % Full flow Flowrate .............. 1.1462 cfs Full flow velocity .............. 5.8376 fps Critical Information Critical depth .................. 5.2817 in Critical slope .................. 0.0050 ft/ft Critical velocity ............... 4.0363 fps Critical area ................... 0.1932 ft2 Critical perimeter .............. 13.9883 in Critical hydraulic radius ....... 1.9894 in Critical top width .............. 6.0000 in Specific energy ................. 0.9155 ft Minimum energy .................. 0.6602 ft Froude number ................... 2.2233 Flow condition .................. Supercritical *PIPE RECEIVES FLOW FROM THE SUM OF PR-1 AND OS-1 10/09/2017 6" PIPE FROM DOWNSPOUT FOR 10-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 6.0000 in Flowrate ........................ 0.2900 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 2.0576 in Area ............................ 0.1963 ft2 Wetted Area ..................... 0.0596 ft2 Wetted Perimeter ................ 7.5076 in Perimeter ....................... 18.8496 in Velocity ........................ 4.8686 fps Hydraulic Radius ................ 1.1425 in Percent Full .................... 34.2939 % Full flow Flowrate .............. 1.1462 cfs Full flow velocity .............. 5.8376 fps Critical Information Critical depth .................. 3.2640 in Critical slope .................. 0.0038 ft/ft Critical velocity ............... 2.6562 fps Critical area ................... 0.1092 ft2 Critical perimeter .............. 9.9529 in Critical hydraulic radius ....... 1.5796 in Critical top width .............. 6.0000 in Specific energy ................. 0.5398 ft Minimum energy .................. 0.4080 ft Froude number ................... 2.4231 Flow condition .................. Supercritical *ROOF 71.6% OF PR-1 AREA, 6" DOWNSPOUT PIPE CALCULATED WITH 71.6% OF PR-1 TOTAL FLOW. 10/09/2017 6" PVC PIPE FROM DOWNSPOUT FOR 100-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 6.0000 in Flowrate ........................ 0.4900 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 2.7401 in Area ............................ 0.1963 ft2 Wetted Area ..................... 0.0874 ft2 Wetted Perimeter ................ 8.9044 in Perimeter ....................... 18.8496 in Velocity ........................ 5.6090 fps Hydraulic Radius ................ 1.4128 in Percent Full .................... 45.6686 % Full flow Flowrate .............. 1.1462 cfs Full flow velocity .............. 5.8376 fps Critical Information Critical depth .................. 4.2824 in Critical slope .................. 0.0044 ft/ft Critical velocity ............... 3.2320 fps Critical area ................... 0.1516 ft2 Critical perimeter .............. 11.9896 in Critical hydraulic radius ....... 1.8209 in Critical top width .............. 6.0000 in Specific energy ................. 0.7173 ft Minimum energy .................. 0.5353 ft Froude number ................... 2.3613 Flow condition .................. Supercritical *ROOF 71.6% OF PR-1 AREA, 6" DOWNSPOUT PIPE CALCULATED WITH 71.6% OF PR-1 TOTAL FLOW. 10/09/2017 4" PVC PIPE FROM TRENCH DRAIN FOR 10-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 4.0000 in Flowrate ........................ 0.1300 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 1.5933 in Area ............................ 0.0873 ft2 Wetted Area ..................... 0.0324 ft2 Wetted Perimeter ................ 5.4640 in Perimeter ....................... 12.5664 in Velocity ........................ 4.0107 fps Hydraulic Radius ................ 0.8542 in Percent Full .................... 39.8315 % Full flow Flowrate .............. 0.3888 cfs Full flow velocity .............. 4.4549 fps Critical Information Critical depth .................. 2.4301 in Critical slope .................. 0.0046 ft/ft Critical velocity ............... 2.3389 fps Critical area ................... 0.0556 ft2 Critical perimeter .............. 7.1435 in Critical hydraulic radius ....... 1.1204 in Critical top width .............. 4.0000 in Specific energy ................. 0.3828 ft Minimum energy .................. 0.3038 ft Froude number ................... 2.2437 Flow condition .................. Supercritical *PIPE FROM TRENCH DRAIN RECEIVES THE SUM OF 20.0% PR-1 FLOW AND OS-1 FLOW 10/09/2017 4" PVC PIPE FROM TRENCH DRAIN FOR 100-YR EVENT Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 4.0000 in Flowrate ........................ 0.2300 cfs Slope ........................... 0.0200 ft/ft Manning's n ..................... 0.0090 Computed Results: Depth ........................... 2.2137 in Area ............................ 0.0873 ft2 Wetted Area ..................... 0.0496 ft2 Wetted Perimeter ................ 6.7114 in Perimeter ....................... 12.5664 in Velocity ........................ 4.6410 fps Hydraulic Radius ................ 1.0633 in Percent Full .................... 55.3426 % Full flow Flowrate .............. 0.3888 cfs Full flow velocity .............. 4.4549 fps Critical Information Critical depth .................. 3.2323 in Critical slope .................. 0.0054 ft/ft Critical velocity ............... 2.9538 fps Critical area ................... 0.0779 ft2 Critical perimeter .............. 8.7479 in Critical hydraulic radius ....... 1.2817 in Critical top width .............. 4.0000 in Specific energy ................. 0.5192 ft Minimum energy .................. 0.4040 ft Froude number ................... 2.1224 Flow condition .................. Supercritical *PIPE FROM TRENCH DRAIN RECEIVES THE SUM OF 20.0% PR-1 FLOW AND OS-1 FLOW 10/09/2017 TRENCH DRAIN CALCULATIONS 10/09/2017 4" TRENCH DRAIN FOR 10-YR EVENT Channel Calculator Given Input Data: Shape ........................... Rectangular Solving for ..................... Depth of Flow Flowrate ........................ 0.1300 cfs Slope ........................... 0.0100 ft/ft Manning's n ..................... 0.0130 Height .......................... 6.0000 in Bottom width .................... 4.0000 in Computed Results: Depth ........................... 2.1089 in Velocity ........................ 2.2192 fps Full Flowrate ................... 0.4763 cfs Flow area ....................... 0.0586 ft2 Flow perimeter .................. 8.2178 in Hydraulic radius ................ 1.0265 in Top width ....................... 4.0000 in Area ............................ 0.1667 ft2 Perimeter ....................... 16.0000 in Percent full .................... 35.1480 % Critical Information Critical depth .................. 2.0140 in Critical slope .................. 0.0113 ft/ft Critical velocity ............... 2.3238 fps Critical area ................... 0.0559 ft2 Critical perimeter .............. 8.0280 in Critical hydraulic radius ....... 1.0035 in Critical top width .............. 4.0000 in Specific energy ................. 0.2523 ft Minimum energy .................. 0.2517 ft Froude number ................... 0.9333 Flow condition .................. Subcritical *TRENCH DRAIN RECEIVES THE SUM OF 20.0% PR-1 FLOW AND OS-1 FLOW 10/09/2017 4" TRENCH DRAIN FOR 100-YR EVENT Channel Calculator Given Input Data: Shape ........................... Rectangular Solving for ..................... Depth of Flow Flowrate ........................ 0.2300 cfs Slope ........................... 0.0100 ft/ft Manning's n ..................... 0.0130 Height .......................... 6.0000 in Bottom width .................... 4.0000 in Computed Results: Depth ........................... 3.2842 in Velocity ........................ 2.5212 fps Full Flowrate ................... 0.4763 cfs Flow area ....................... 0.0912 ft2 Flow perimeter .................. 10.5683 in Hydraulic radius ................ 1.2430 in Top width ....................... 4.0000 in Area ............................ 0.1667 ft2 Perimeter ....................... 16.0000 in Percent full .................... 54.7359 % Critical Information Critical depth .................. 2.9461 in Critical slope .................. 0.0132 ft/ft Critical velocity ............... 2.8105 fps Critical area ................... 0.0818 ft2 Critical perimeter .............. 9.8922 in Critical hydraulic radius ....... 1.1913 in Critical top width .............. 4.0000 in Specific energy ................. 0.3725 ft Minimum energy .................. 0.3683 ft Froude number ................... 0.8496 Flow condition .................. Subcritical *TRENCH DRAIN RECEIVES THE SUM OF 20.0% PR-1 FLOW AND OS-1 FLOW 10/09/2017 INLET CAPACITY CALCULATIONS 10/09/2017 10/09/2017 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10Capacity (cfs)Head (ft) Nyloplast 6" Drop In Grate Inlet Capacity Chart 10/09/2017 DRYWELL WQCV 10/09/2017 Volume to Width of Depth of gravel Dia of Percent Detain (cf) Gravel (ft) Below M.H. (ft) M.H. Voids (%) 514 2 1 6 30 Area of M.H. (sqft) 28.3 Area of Gravel (sqft) 59.7 Depth Volume of Vol of Gravel Vol of Drywell Vol of Drywell Vol of Total Volume Varied Gravel Voids Conic Section Cyl. Section Drywell Volume Met (ft) (cf) (cf) (cf) (cf) (cf) (cf) 3 44.2 13.2 0.0 28.3 28.3 41.5 no 4 103.8 31.1 0.0 56.5 56.5 87.7 no 5 163.5 49.0 0.0 84.8 84.8 133.9 no 6 223.1 66.9 0.0 113.1 113.1 180.0 no 7 282.8 84.8 0.0 141.4 141.4 226.2 no 8 342.5 102.7 0.0 169.6 169.6 272.4 no 9 402.1 120.6 0.0 197.9 197.9 318.6 no 10 461.8 138.5 0.0 226.2 226.2 364.7 no 11 521.4 156.4 0.0 254.5 254.5 410.9 no 12 581.1 174.3 0.0 282.7 282.7 457.1 no 13 640.8 192.2 0.0 311.0 311.0 503.2 no 14 700.4 210.1 0.0 339.3 339.3 549.4 Meets Min. DRYWELL SHALL BE 14 ft. Deep Transmissivity Calc. AP=(VR)/(K)(43,200) AP=Total area of sides = 348.54 available VR = runoff volume =514 K= Hydraulic conductivity of Soil 0.000046 . AP=258.655395 Drywell Calculations 1517 Blake Avenue, Suite 101 Glenwood Springs, CO 81601 Calculation of Drywell and Gravel for Drywell HCE# 2161062.00 J:/sdskproj/216/1062/excel/dry well-2-24-17.xls Lot 14 15 McSkimming Drive Road DRYWELL DRAINAGE CALCULATION February 27, 2017 Variables 10/09/2017 Volume to Width of Depth of gravel Dia of Percent Cone Height Detain (cf) Gravel (ft) Below M.H. (ft) M.H. Voids (%) (ft) 101 0 0 6 30 0 Area of M.H. (sqft)28.3 Area of Gravel (sqft)0.0 Depth Volume of Vol of Gravel Vol of Drywell Vol of Drywell Vol of Total Volume Varied Gravel Voids Conic Section Cyl. Section Drywell Volume Met (ft) (cf) (cf) (cf) (cf) (cf) (cf) 2 0.0 0.0 0.0 56.5 56.5 56.5 no 3 0.0 0.0 0.0 84.8 84.8 84.8 no 4 0.0 0.0 0.0 113.1 113.1 113.1 Meets Min. 5 0.0 0.0 0.0 141.4 141.4 141.4 Meets Min. 6 0.0 0.0 0.0 169.6 169.6 169.6 Meets Min. 7 0.0 0.0 0.0 197.9 197.9 197.9 Meets Min. 8 0.0 0.0 0.0 226.2 226.2 226.2 Meets Min. 9 0.0 0.0 0.0 254.5 254.5 254.5 Meets Min. 10 0.0 0.0 0.0 282.7 282.7 282.7 Meets Min. 11 0.0 0.0 0.0 311.0 311.0 311.0 Meets Min. 12 0.0 0.0 0.0 339.3 339.3 339.3 Meets Min. 13 0.0 0.0 0.0 367.6 367.6 367.6 Meets Min. 14 0.0 0.0 0.0 395.8 395.8 395.8 Meets Min. 15 0.0 0.0 0.0 424.1 424.1 424.1 Meets Min. 1517 Blake Avenue, Suite 101 Glenwood Springs, CO 81601 Tele: (970) 945-8676 - Fax (970) 945-2555 14 Inverness Drive East Suite F-120 Englewood, CO 80112 Tele: (303) 925-0544 - Fax (303) 925-0547 Therefore, install upper chamber of 4.0' depth to 14' deep 6' diameter drywell for stormwater detention PROPOSED BASIN 1 (PR-1) WQCV CALCULATION j:/216/1819.01/excel/drywellwqcv.xlsMarch 10, 2017 HCE# 2161819.01 Variables Calculation of Drywell and Gravel for one Drywell Note: Drywell depth begins 1.0' below surface (1.0' of topsoil) 10/09/2017 ASPEN CHARTS AND FIGURES 10/09/2017 City of Aspen Urban Runoff Management Plan Chapter 2 - Rainfall 2-4 Rev 9/2014 Note: Accuracy is more reliable at 5 minute increments. Figure 2.1 IDF Curves for Aspen, Colorado 0 1 2 3 4 5 6 7 0 5 10 15 20 25 30 35 40 45 50 55 60Intensity (inch/hr)Duration in Minutes Rainfall IDF for Aspen, Colorado 2‐yr 5‐yr 10‐yr 25‐yr 50‐yr 100‐yr 10/09/2017 City of Aspen Urban Runoff Management Plan Chapter 2 - Rainfall 2-2 Rev 9/2014 into thunderstorms. Autumn in Aspen is usually dry and warm and during September daytime temperatures can reach 70°F, but night temperatures can drop to freezing. Aspen is renowned for its warm winter sun. Winter daytime temperatures typically range from 20 to 40°F in the City and from 10 to 30°F on the mountain. Once the sun goes down, the temperature drops dramatically. Table 2.1 presents monthly statistics for temperature, precipitation, snowfall, and snow depth in the Aspen area. Table 2.1 Monthly Statistics for Temperature and Precipitation in Aspen Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average Max. Temperature (F) 35 39 45 52 63 72 78 76 69 58 43 35 55.5 Average Min. Temperature (F) 9.1 12 20 26 35 41 47 46 39 30 19 9.7 27.7 Average Total Precipitation (in.) 1.7 2.1 2.7 2.5 2.1 1.4 1.8 1.6 2.1 2 2.6 1.9 24.37 Average Total Snowfall (in.) 25 27 28 20 7.8 1 0 0 1 11 28 25 173.8 Average Snow Depth (in.) 21 28 27 12 1 0 0 0 0 1 6 14 (Source: Station 050372 at Aspen 1 SW, Colorado) 2.3 Rainfall Depth, Duration, Frequency, and Intensity The rainfall intensity-duration-frequency (IDF) curve is a statistical formula to describe the relationship among the local rainfall characteristics and return periods. The IDF curve is used in the Rational Method for peak runoff predictions of basins smaller than 90 acres. Based on the NOAA Atlas Volume 3, the IDF curve for the City of Aspen can be derived according to the locality and elevation. The City of Aspen is located at approximately 39°11′32″N and 106°49′28″W, at an elevation of approximately 8,100 feet. Based on depth and duration data (Appendix B, Table 1), rainfall intensities can be calculated for various frequencies. Rainfall intensity data, which form the basis of the Intensity-Duration-Frequency (IDF) curves in Figure 2.1 are provided in Table 2.2. Table 2.2 Rainfall Intensity-Duration-Frequency in Aspen, Colorado Return Rainfall Intensity in inch/hr for Various Periods of Duration Period 5-min 10-min 15-min 30-min 1-hr (P1) 2-hr 3-hr 6-hr 24-hr 2‐yr 2.06 1.51 1.23 0.77 0.47 0.28 0.21 0.13 0.06 5-yr 2.98 2.17 1.77 1.09 0.64 0.36 0.26 0.16 0.07 10-yr 3.72 2.72 2.22 1.35 0.77 0.43 0.30 0.18 0.08 25‐yr 4.75 3.47 2.82 1.71 0.95 0.53 0.36 0.21 0.09 50‐yr 5.53 4.05 3.30 1.98 1.09 0.60 0.41 0.24 0.11 100-yr 6.32 4.63 3.76 2.24 1.23 0.67 0.45 0.26 0.12 Using the data in Table 2.2 (derived from NOAA Atlas 14 Volume 8), the following equation was derived that can be used to determine intensities not shown in the IDF table or curve: 052.1 1 )10( 8.88 dT PI (Equation 2-1) Where, I = rainfall intensity (inch/hr), P1 = 1-hr rainfall depth (inches), and Td = duration or time of concentration (minutes). 10/09/2017 City of Aspen Urban Runoff Management Plan Chapter 3 - Runoff 3-6 Rev 10/2014 Figure 3.2 – Runoff Coefficients for NRCS Hydrologic Soil Group A Figure 3.3 – Runoff Coefficients for NRCS Hydrologic Soil Group B 10/09/2017 City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-33 Rev 8/2009 Figure 8.13 Aspen Water Quality Capture Volume 10/09/2017 City of Aspen Urban Runoff Management Plan Chapter 3 - Runoff 3-2 Rev 2/2010 Figure 3.1 Natural Resource Conservation Service (NRCS) Soil Map for Aspen 10/09/2017