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Home My WebLink AboutFile Documents.1010 E Hyman Ave.0025-2022-BCHO (20) Final Drainage Report 1010 E. Hyman Avenue February 24, 2023 Reviewed by Engineering 03/24/2023 9:35:37 AM "It should be known that this review shall not relieve the applicant of their responsibility to comply with the requirements of the City of Prepared for: Aspen. The review and approval by the City is offered only to assist the applicant's Susi Marilee E Revocable Trust understanding of the applicable Engineering 7806 Charney Lane requirements." The issuance of a permit based Boca Raton, FL 33496 on construction documents and other data shall not prevent the City of Aspen from requiring the correction of errors in the construction documents and other data. Prepared by: .. RIVERCITY C n N S U LTA N T S 215 Pitkin Ave, Unit 201 Grand Junction, CO 81501 Phone: (970) 241-4722 Fax: (970) 241-8841 Job No. 2008-001 GRAND JUNCTION,COLORADO 81501■970.241.4722 , 1/2 0 2 3 ASPEN BUILDING DEPARTMENT TABLE OF CONTENTS Engineer's Certification 2 I. Introduction 3 A. Background 3 B. Project Location 3 C. Project Description 3 D. Previous Investigations 4 II. Drainage System Description 4 A. Existing Drainage Conditions 4 B. Master Drainage Plan 4 C. Offsite Tributary Area 4 D. Proposed Drainage System Description 4 E. Drainage Facility Maintenance 7 III. Drainage Analysis and Design Criteria 8 A. Regulations 8 B. Variance from Criteria 8 IV. Post Construction Stormwater Management 8 A. Stormwater Quality Control Measures 8 B. Stormwater Quality Calculations 8 V. Conclusions 8 A. Compliance with Manual 8 B. Design Effectiveness 8 C. Areas in Flood Hazard Zone 8 D. Variances from Manual 9 VI. References 9 APPENDIX Project Site Information (FIRM Panel, Soils Data) A URMP Calculations B Operation and Maintenance Agreement C EIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501■970.241.4722 • 1/2023 Page 1 ASPEN BUILDING DEPARTMENT Engineer's Certification I hereby certify that the Drainage Report for the design of 1010 E. Hyman Avenue was prepared by me, or under my direct supervision, in accordance with the provisions of the Urban Runoff Management Plan (URMP) (Rev. December 2014) for the owners thereof. I understand that the City of Aspen does not and will not assume liability for drainage facilities designed by others. wei ��v SpVTy ot$�� 6012 Paul J. Southworth, P.E. State of Colorado Reg. No. 60123 EIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 03 01/2023 Page 2 ASPEN BUILDING DEPARTMENT I. Introduction A. Background The purpose of this Drainage Report is to identify pre-development and post-development drainage conditions for the proposed site improvements at 1010 E. Hyman Avenue. This report identifies the following items with respect to the site: • existing drainage patterns and issues • developed drainage patterns • potential drainage issues resulting from development • solutions to the potential drainage issues • design of the various elements of the storm drain system for the site • stormwater water quality requirements • post construction BMP's B. Project Location The proposed project site is located at 1010 E. Hyman Avenue in Aspen, CO (Parcel No. 273718147002) The Property is one-half of a duplex with associated landscaping and hardscape, on a 6,000 square foot lot owned and maintained by the Pine Glen Townhouse Condo Association. This drainage report and the proposed improvements are considered with the western half of the duplex, approximately 3,00 square feet, owned by the Susi Marilee E Revocable Trust. The duplex unit consists of two above-ground floors and a below- grade finished basement. The project site is abutted to the south by E. Hyman Ave right-of-way consisting of approximately 12-feet of arboraceous landscaped area, 7.5-feet of concrete curb, gutter & attached sidewalk to the paved asphalt roadway. The rear (north) side of the site is abutted by an approximately 22-foot-wide gravel public alley. The western and eastern sides of the project abut similar residential duplexes. C. Project Description Proposed improvements to the site include both interior remodeling and exterior site improvement. Significant water intrusion into the basement level is present in the existing condition. A primary component of the proposed design is resolution of the water intrusion issue. The exterior improvements include replacement and realigning of existing hardscape walkway, removal of and/or replacement of side window wells, removal of one tree to be replaced with the planting of one new tree, waterproofing of the foundation, construction of two dry wells with associated on-site storm drain, upgrade to electrical service, and associated landscaping. The total exterior area of disturbance is measured as 1,088 square feet. EIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501■970.241.4722 03 e1/2023 Page 3 ASPEN BUILDING DEPARTMENT There are no mapped FEMA Floodplains within the project site. The project site is within a Zone X — Area of Minimal Flood Hazard. There is a mapped Zone AE-Floodway approximately 250-ft to the east (Roaring Fork River) A FEMA FIRM Map for the area is available in Appendix A. D. Previous Investigations No previous investigations involving the project parcel are known to exist. A geotechnical investigation was performed by Kumar & Associates as a part of this project. The results of this investigation are discussed in the Proposed Drainage System Description below. A full copy of the results can be found in Appendix A. II. Drainage System Description A. Existing Drainage Conditions The front (south) of the site is a shared common area consisting of pervious earth, mature coniferous and deciduous trees, hardscape walkway and a window well. Downspouts discharge at grade. The front of the site's topography generally slopes between 3-7% southerly to the right-of-way and westerly to the abutting parcel. The two parcels are separated by a short timber retaining wall. The other half of the duplex's front yard slopes southwesterly towards the public right-of-way. Once in the right-of-way, runoff is carried westerly by the City's concrete curb and gutter to the nearest inlet at the intersection of S Original St and E Hopkins Ave approximately 1,020 linear feet from the site's point of discharge. The City's stormwater system then into the Roaring Fork River. The western portion of the site consists of an approximately 7-foot wide strip of hardscape walkway and landscaped area around several basement level window wells. Topography typically slopes westerly at 3-8% onto the abutting neighbor. The northern rear portion of the site consists of a shared paved driveway sloping at approximately 12% out to the rear gravel alley. The eastern portion of the site is occupied by the other half of the duplex. Overland flows from the adjoining duplex owner slopes southwesterly towards the public right-of-way. The existing impervious area for the site including building, driveway, walkways, and window wells is calculated as approximately 2,140 square feet. B. Master Drainage Plan No "Master Drainage Plan" is known to exist for the subject property. C. Offsite Tributary Area Given the existing topography, no off-site tributary areas flow onto the project site. D. Proposed Drainage System Description The proposed project's drainage system will include lot grading, dry wells, and storm drain, and foundation drain. The existing foundation has a significant water infiltration problem. EIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 • 1/2023 Page 4 ASPEN BUILDING DEPARTMENT Therefore this system was designed to maximize the amount of water conveyed away from the foundation to increase the likelihood of alleviating the problem. The main BMP for treating the water quality capture volume as well as 100-year detention will be a 7-foot diameter dry well placed in the front yard of the project site. The drywell will consist of two chambers conforming to the detail shown in Figure 8.69 of the URMP. Runoff landing on the roof will be collected and piped directly into the drywell. Surface runoff from the side and front of the site will be graded to flow to area inlets and piped directly into the dry well. A grated cover will be installed to collect surface runoff in the immediate vicinity of the dry well. The drywell is designed to hold the required detention volume. In the unlikely event of failure, the overflow route for the runoff is thru the surface grate and out to the public right-of-way. No improvements are being made to the existing driveway which flows to the alleyway to the north of the project site. Thus, the drainage pattern of the driveway will remain unchanged. Please see the construction plans for the dry well detail and proposed connectivity. A second 4-foot diameter dry well will installed to collect discharge from the building's foundation drain. The foundation drain dry well and surface runoff dry well will not be connected to each other to eliminate the possibility of primary runoff backing up into the foundation drains in accordance with engineering best management practices. The surface runoff dry well will also be placed as far away from the structure, to the maximum extent practicable,to alleviate the existing water intrusion problem into the basement level. Waterproofing of the foundation is being performed to further alleviate the water intrusion problem. The smaller 4-foot diameter foundation drain dry well is anticipated to collect nuisance level flows from the foundation drain only. The primary 7-foot surface diameter dry well was sized in accordance with URMP guidelines for capturing the 100-year detention volume. The minimum percolation area and drawdown time was sized/calculated using URMP guidelines and the results of Kumar & Associates geotechnical investigation. The sizing and geotechnical results are described below. The proposed impervious area for the site including building, driveway, walkways, window wells, and the dumpster enclosure concrete pad is calculated as approximately 2,160 square feet or less than a 1% increase in impervious area. For all intents and purposes, this less than 1% increase is considered negligible and thus the percent impervious is considered equal in the existing and proposed condition. Of the proposed impervious area, all but the rear driveway (-489 square feet), that will remain untouched in the proposed design, is routed to the proposed dry well system. Thus, approximately 1,671 square feet of impervious area is routed to the proposed dry well. The primary dry well is being sized to capture and infiltrate the 100-year detention volume. Per section 8.5.4.2, a dry, "a drywell without a controlled outlet, utilized for detention, must capture the entire storm runoff volume. The design storm runoff volume shall be conservatively estimated by multiplying the one hour design storm depth by the total impervious area tributary to the drywell." For conservatism, the entire site's impervious area was used to calculate the 100-year detention volume. A total site imperviousness of 2,160 square feet multiplied by the 100-year, 1-hour depth of rainfall for Aspen (1.23 EIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 03 e1/2023 Page 5 ASPEN BUILDING DEPARTMENT inches) and converted to cubic feet equates to 221.4 cubic feet of detention volume required. See Appendix B for detailed calculations. The soils report recommended that drywell perforations be placed no higher than the basement floor level elevation and that the drywell must be placed at least five-feet away from the building's foundation. For this reason, drywell perforations are designed to begin at elevation 7931.25. A minimum four-foot tall, perforated section is required per URMP Figure 8.69 placing the bottom of the dry well at elevation 7927.25. With a grate design rim elevation of 7939.30, this makes the drywell approximately 12.05-feet tall, exceeding the URMP's 10-ft tall depth requirement from the ground surface. Because of the size of the required volume, a larger diameter drywell that does not use cone sections was anticipated to be required. Thus, only the riser barrel and perforated barrel section was used to calculate the captured stormwater volume. Using the depths required by the soils report, and an assumed 3.25 tall section for grate, frame, and raising of the frame to grade, an approximately 8.8-foot tall riser and perforated barrel section was used to size the primary dry well. A 7-foot diameter dry well was selected providing 338.7 cubic feet of storage volume. The proposed drywell is designed to be surrounded by 18-inches of 3/4" washed, crushed stone wrapped in a non-woven geotextile fabric. A chamber separating the perforated barrel section and riser section is included per URMP Figure 8.69. Inlet pipes are designed to enter above the chamber separator at elev. 7933.30. Calculations showing adequate pipe capacity at 80% full are provided in Appendix B. Given the depth of the proposed drywell and the small available site footprint, the desire to protect mature existing vegetation, and the soils report recommendations, the resultant available area for construction of the two drywells resulted in setbacks to foundation and property lines less than the 10-foot required by City of Aspen. The two drywells were sited within the allowable limits of disturbance to meet a minimum 5-foot setback to foundation as noted in the soils report. This resulted in setbacks from drywells to E. Hyman property line (right-of-way) of 4.5-feet, to foundation at 5.7-feet and to west property line at 5.3-feet. To eliminate the potential for underground cross lot water flow, the western half of the primary drywell will have its perforations plugged by a coating of hydraulic waterproofing cement on the inside of the drywell. The foundation drywell is further than 10-ft from the west property line and will not have its perforations sealed. A variance request for the setback distances has been submitted to the Engineering Department under separate cover. The geotechnical report determined a percolation rate of 2 minutes/inch or 30 inches/hour exceeding the URMP minimum requirement of 3 inches/hour. To verify the percolation area of the stone was large enough to meet URMP requirements, the rearranged Darcy equation specified in URMP section 8.5.4.2 used. The rearranged equation assumes a 24-hour drawdown time, a hydraulic gradient of 1.0, and a 50% clogging factor. The rearranged equation is provided below EIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 • 1/2023 Page 6 ASPEN BUILDING DEPARTMENT Vr AP = (K) *43,200 AP = Percolation Area,square feet Vr = Runoff volume,cubic feet K = hydraulic conductivity per percolation test results,fps A 30 inches/hr percolation rate is equivalent to 0.0007 fps. For a 100-year detention volume of 221.4 cubic feet,the rearranged Darcy equation requires a minimum percolation area of 7.38 square feet. A 7-foot diameter dry well with 8-inch thick walls, surrounded by 18-inches of 3/4"washed, crushed stone will provide a bottom surface area for the stone of 100.88 square feet. After subtracting out the area of stone that will be impacted by the hydraulic waterproofing cement impermeable coating between the dry well and the west property line as well as the area of stone that overlaps with the 4-foot foundation drain dry well percolation area, an uninhibited percolation area of 13.91 square feet remains. Thus, the minimum required percolation area of 7.38 square feet is met. See Appendix B for detailed calculations. All cross-lot drainage has been eliminated by the proposed design. Given the equivalent amount of impervious area in the existing and proposed design condition, and the proposed addition of a combined WCQV/detention dry well BMP, all design storms up to and including the 100-year event, feature smaller runoff rates in the proposed condition compared to the existing condition. E. Drainage Facility Maintenance Ownership and maintenance of the proposed drainage improvements within private property will be owned and maintained by the Property Owner and/or Property Owner's Association. The developed drainage for the site has been designed to minimize maintenance. There are no mechanical items to check and maintain. Anticipated maintenance includes periodic (1-2 times per year and as needed after major storm events) clearing of debris from inlets and grates. Periodic sediment removal from the drywell pond may also be required. The removal frequency will vary depending on the sediment removal loading through the system, but it is unlikely sediment removal would be required more often than once every 5 to 10 years. Inspection of the drainage facility and associated BMPs shall be conducted annually and after every storm exceeding 0.5 inches. Sediment, debris/trash, and any other waste material removed from a dry well shall be disposed of at suitable disposal sites and in compliance with local, state, and federal waste regulations. The drain-time of the dry well shall be routinely evaluated to ensure the maximum time of 24 hours is not being exceeded. If drain-down times are exceeding the maximum, drain the dry well via pumping and clean out the percolation area (the percolation barrel may be jetted to remove sediment accumulated in perforations). Consider drilling additional perforations in the barrel. If slow drainage persists, the system may need to be replaced. A signed Operation and Maintenance Agreement is provided in Appendix C. EIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 • 1/2023 Page 7 ASPEN BUILDING DEPARTMENT Ill. Drainage Analysis and Design Criteria A. Regulations The policy, design criteria, design constraints, methods of analysis, recommendations, and conclusions presented in this report are in conformance with standard engineering practice and the URMP (date December 2014). B. Variance from Criteria A variance request under separate cover for setback distances for drywells from property lines, right-of-way, and structures is provided under separate cover to the Aspen Engineering Department. No other variances from the URMP are requested. IV. Post Construction Stormwater Management A. Stormwater Quality Control Measures The drywell has been designed to contain and infiltrate the 100-year detention volume without overtopping. B. Stormwater Quality Calculations The proposed dry well has been sized for the 100-year detention volume, exceeding the WQCV requirements. V. Conclusions A. Compliance with Manual The policy, design criteria, design constraints, methods of analysis, recommendations, and conclusions presented in this report are in conformance with standard engineering practice and the URMP (dated December 2014). B. Design Effectiveness This design will be very effective for controlling runoff from this site and will provide stormwater quality measures. All cross-lot drainage has been eliminated. Given the equivalent amount of impervious area in the existing and proposed condition design, and the proposed addition of a detention dry well BMP, all design storms up to and including the 100-year event feature smaller runoff rates than in the proposed condition compared to the existing condition. C. Areas in Flood Hazard Zone There are no mapped FEMA Floodplains within the project site. The project site is within a Zone X — Area of Minimal Flood Hazard. There is a mapped Zone AE-Floodway approximately 250-ft to the east (Roaring Fork River) A FEMA FIRM Map for the area is available in Appendix A. EIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501■970.241.4722 03 01/2023 Page 8 ASPEN BUILDING DEPARTMENT D. Variances from Manual A variance request under separate cover for setback distances for drywells from property lines, right-of-way, and structures is provided under separate cover to the Aspen Engineering Department. No other variances from the URMP are requested. VI. References 1. Urban Rainfall Management Plan, December 2014 2. FEMA Flood Map Service Center website, https://msc.fema.gov/portal . EIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501■970.241.4722 03 01/2023 Page 9 ASPEN BUILDING DEPARTMENT APPENDIX A Project Site Information 1. FEMA Firm Panel 2. Soils Report 3. NRCS Soil Survey— Hydrologic Soil Group RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT National Flood Hazard Layer FIRMette - FEMA Legend 106°49'2"W 39°11'30"N SEE EIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT 1g1'F• ,Lv°ne vAV �w f 'r I, • ` IPl 11,1 N COUNTY Without Base Flood Elevation(BFE) . Zone A,V.A99 _ ~"1'^ 1 With BFE or Depth Zone AE,AO.AH,VE,AR Zone m. �tL4-• l�Sl_S7 t SPECIAL FLOOD p 4 4 f A ^ 1�^W�, ` � I'� II HAZARD AREAS Regulatory Floodway ^^-.1 ), ()MAI Ay 1, .T ----- _>184 FEET , • • • 0.2%Annual Chance Flood Hazard,Areas • L .NC'J i 1 of 1%annual chance flood with average O'erION Fit depth less than one foot or with drainage �• 1 r •, • areas of less than one square mile zone 9'c^ TICS R84W 5007 Future Conditions 1%Annual ... .. �� 'r • , ,4 - • +•�� Chance Flood Hazard zonex FLOODW., 2 8 F41 /, � T LC�' �" Area with Reduced Flood Risk due to 1.� Zr�a92 FEE 1,� ` ' �`/1 , OTHER AREAS OF Levee.See Notes.zone x Qr• — t I ` • ,' FLOOD HAZARD �� Area with Flood Risk due to LeveezoneD Zor(<"E �1 4 �� Sr • J. Al a c;` • 1 to ' ,,,b., (ct,,, ,,n(�,- �� • NO SCREEN Area of Minimal Flood Hazard zonex • ►r p5� (t/ Zone ~ �4 *� Effective LOMRs i •0809700354E •• �` 4- FL , (` W - &f/ t - 08097C0358E t Jr. _ A OTHER AREAS Area of Undetermined Flood Hazard Zone ' '4 ,\ ,�- FLO ti�IVLL.Y —4u .. Ilk 41.` • lioeff. 8/15/2019�c� a�zo"Erw--, . eff.8/15/2019 Z • -_- Zorr-1E er.Zol;4E�� (- At gla GENERAL - - Channel,Culvert,or Storm Sewer . P. ♦ • - f�• ^;�919FE j f` _ STRUCTURES I I I I I Levee,Dike,or Floodwall �. 1 ,„„ 4, i ,, .. • •• „. I .� �g,9�� V . 1 1 4 1 + 0 20.2 Cross Sections with 1%Annual Chance -.�waiti AREA OF MINIMAL FLOOD HAZARD * 4, ?9 9�5 s•T A, 1 , e- — Coastal Transect er Surface levation 1fs�3 - Base Flood Elevation Line BFE 40 Zane X FFEr I:I'. ! (BFE) . : ,7931 FEET ' , I • I Limit of Study �. 'I' l 0 F. L P N *' lit 1 , _ 1 No•• Jurisdiction Boundary " ~ 080143 '�4la ' ►(� !l , * 7934 FEET .i - — Coastal Transect Baseline OTHER - — Profile Baseline •I• • �6 r, � • /0 �� ' FEATURES Hydrographic Feature ► + 7�0� �. 1.� ` • Digital Data Available • L .",thip ii tr . b•►,,.EET Digital Data Available F N ,„.ts 7 � ,ry `'•/J F� :E • � I MAP PANELS9 Unmapped T1oS RMW 5018 "Ilk .� FLOODWAY•w I ` .. �' ,,,, „`!rQE The pin displayed on the map is an approximate ,...* 7SQ6 FE� 11 if \ point selected by the user and does not represent r� A , an authoritative property location. r# Zone AE 0 7948 *� • j ` This map complies with FEMA's standards for the use of • \ It-4. .A. • 1 fi�ET 1• / V digital flood maps if it is not void as described below. A � The basemap shown complies with FEMA's basemap v 'al 0 �. i ,08097C0362E.� 0809700366E / accuracy standards • . eff.8/15/2019 ; •. 7952 ET eff.8/15/2019 t \ The flood hazard information is derived directly from the . . i FE ,� authoritative NFHL web services provided by FEMA.This map • ` •� � t ., was exported on 1/11/2023 at 4:18 PM and does not ,"- • sir Z FEE w reflect changes or amendments subsequent to this date and j 79`�,6,'r�t 1 time.The NFHL and effective inf ,� •` '.�Y become superseded by new dat N. ! _ �. a i: ► This map image is void if the one or more of the following map itir * a 796 1 1 v • # 4 elements do not appear:basemap i ry, Q zpDg �,,�\~ �'_ Jiiiikidiaillt . - legend,scale bar,map creation dat6 r)hiM'j i,9e44i0s3 106°48'25"W 39°ll'2"N FIRM panel number,and FIRM effective date.Map images for Feet 1:6 000 unmapped and unmodernized areas cannoApAtsad•tor 0 250 500 1,000 1,500 2,000 regulatory purposes. 1or``iN Basemap:USGS National Map:Orthoimagery:Data refreshed October,2020 BUILDING DEPARTMENT I( Kumar&Associates,Inc.° Geotechnical and Materials Engineers 5020 County Road 154 and Environmental Scientists Glenwood Springs,CO 81601 phone: (970)945-7988 fax:(970)945-8454 email:kaglenwood@kumarusa.com An Employee Owned Company www.kumarusa.com Office Locations: Denver(HQ),Parker,Colorado Springs,Fort Collins,Glenwood Springs,and Summit County,Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED REMODEL AND LANDSCAPE 1010 EAST HYMAN AVENUE ASPEN, COLORADO PROJECT NO. 21-7-655 SEPTEMBER 23, 2021 PREPARED FOR: MARILEE SUSI 7806 CHARNEY LANE BOCA RATON,FLORIDA 33496 C/O MONIQUE AGNEW (mo@maarchdesign.com) RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 1 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 2 - FOUNDATION BEARING CONDITIONS - 2 - DESIGN RECOMMENDATIONS - 3 - FOUNDATIONS - 3 - FOUNDATION AND RETAINING WALLS - 4 - FLOOR SLABS - 5 - UNDERDRAIN SYSTEM - 5 - SURFACE DRAINAGE - 6 - LIMITATIONS - 6 - FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 - GRADATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS TABLE 2 -PERCOLATION TEST RESULTS RECEIVED ^'.,- /OO-l_-/2 23 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed remodel and landscape to an existing residence located at 1010 East Hyman Avenue in Aspen, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Marilee Susi dated August 5, 2021. An exploratory boring was drilled to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The existing western unit of the two-story duplex residence will be remodeled and landscaping improved. Architectural plans updated May 29, 2021 indicate two window wells will be removed and new stairs to the roof constructed in their place. New hardscape, a trash enclosure, and drywell will also be constructed. Grading for the structures is assumed to be relatively minor to moderate with cut depths up to about 10 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The subject site is developed with a two-story duplex over a basement with an attached garage as shown on Figure 1. The ground surface is variable and the driveway slopes down about 8 degrees to the north, to the west of the residence the slopes range from 2 to 5 degrees down to the northeast to southwest with the slope steepening up to about 15 degrees down to the west near the western property line. The front yard is relatively flat to gently sloping down 1 to 2 degrees to the northwest. Vegetation consists of landscaped plants and mature pines in the front yard and various shrubs,bushes and smaller trees to the west of the residence. The adjoining duplex has a relatively small depression within the front yard window well andREIr EIVED possibly pond surface water runoff 03/01/2023 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT -2 - FIELD EXPLORATION The field exploration for the project was conducted on August 13, 2021. One exploratory boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted CME- 45B drill rig. The boring was logged by a representative of Kumar&Associates, Inc. Samples of the subsoils were taken with a 1%-inch inner diameter spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about 101/2 feet of loose to medium dense, silty to clayey, sand and gravel fill with scattered cobbles and organics overlying natural, medium dense, clean to silty, fine-to medium-grained sand down to the maximum explored depth of 16 feet. Laboratory testing performed on samples obtained from the boring included natural moisture content and gradation analyses. Results of gradation analyses performed on small diameter drive samples (minus 3/4-inch fraction) of the granular subsoils are shown on Figure 3. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were moist. FOUNDATION BEARING CONDITIONS The natural granular soils encountered below the existing fill (and possibly at basement level) are adequate for support of spread footing foundations. Existing fill presents risk of post- construction movement and is unsuitable for support of new foundations. New foundations should extend down to the underlying, natural granular soils. Alternatively, up to 5 feet of compacted structural fill can be placed below new foundations after complete removal of the existing fill. The structural fill should be compacted to at least 98% of standard Proctor density at near optimum moisture content. Caution should be paid to when compacting fill adjacent the existing basement wall. Newly compacted fill and new foundations should not apply excessive lateral forces to the existing basement wall, which may cause subsequent cracking and otRE CE IVE D distress. 03/01/2023 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT - 3 - The City of Aspen requires an engineered excavation stabilization plan if proposed foundations are within 15 feet of a neighboring structure or public travel way. The plan is not required if excavations are less than 5 feet below existing grades or further than 15 feet from travel ways and less than 15 feet deep. Slope bracing through use of a variety of systems such as micro-piles and soil nailing should be feasible at the site. A shoring contractor with experience in the area should provide design drawings to support the proposed excavation slopes. Other City requirements may also be applicable. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural granular soils or compacted structural fill. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural granular soils or on a maximum of 5 feet of newly compacted, moistened structural fill should be designed for an allowable bearing pressure of 2,000 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. 2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 42 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) All existing fill, debris, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing areas should then be moistened and compacted. If water seepage is encountered, the footing areas ��►► should be dewatered before concrete placement. RECEIVED 03/01/2023 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT -4 - 6) A representative of the geotechnical engineer should evaluate fill placement for adequate compaction and observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site granular soils. Cantilevered retaining structures which are separate from the residence (if any) and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. Backfill should not contain organics, debris, or rock larger than 6 inches. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill. We recommend pervious granular soils for backfilling foundation walls and retaining structures because their use results in lower lateral earth pressures and the backfill can be incorporated into the underdrain system. Subsurface drainage recommendations are discussed in more detail in the "Underdrain System" section of this report. Imported granular wall backfill should contain less than 15%passing the No. 200 sieve and have a maximum size of 4 inches. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calcul. `L,1 CE IVE J based on a coefficient of friction of 0.45. Passive pressure of compacted backfill against he �,J 33 /n1 /nn23 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT - 5 - sides of the footings can be calculated using an equivalent fluid unit weight of 400 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a granular material compacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil and existing fill, are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement, floor slabs constructed on native granular soils or compacted structural fill should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4-inch layer of free-draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50%retained on the No. 4 sieve and less than 2%passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1%to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2%passing the No. 200 sieve, less than 50%passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep. If the existing drains are to be used for the new construction, we recommend the drains bRE CE IVE checked for uninterrupted and positive flow by gravity to suitable outlet. 03/01/2023 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT - 6 - DRYWELL Drywells and bio-swales are often used in the Aspen area for site water runoff detention and disposal. The natural granular soils encountered below the fill soils are typically relatively free draining and should be suitable for surface water treatment and disposal as needed. The results of percolation testing performed in Boring 1,presented in Table 2, indicate an infiltration rate of around 2 minutes per inch (60 feet per day inverted equivalent units) for the sand soils found below basement level. Bedrock and groundwater levels are expected to be relatively deep and not affect drywell or bio-swale design. Drywells should have solid casing down to at least 2 feet below basement floor level with perforations below that level and located at least 5 feet from footing edges. If bio-swales are used, they should be designed for the clayey backfill soil conditions and very slow percolation rate. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the remodel and landscaping have been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with at least 2 feet of the on-site soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtajnec1 E 1VE n from the exploratory boring drilled at the location indicated on Figure 1, the proposed type of 03/01/2023 Kumar&Associates,Inc.° Project No.21-7-655 .\SPEN BUILDING DEPARTMENT - 7 - construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory boring and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & Associates, Inc. 1 &a Mark Gayeski, E.I.T. Reviewed by: 400"• • �� Steven L. Pawlak, '.EEy 15222 • i SLP/kac %,is l � �, �' •G$" Cc: (ferry@steeple:'i,•alilisNNNNNNNNN RECEIVED 03/01/2023 Kumar&Associates,Inc.® Project No.21-7-65ASPEN BUILDING DEPARTMENT ALLty �L BORING 1 ..10. _ ____ .0e, ill , 4 , 0: ? !•14 '_ liP 10 / 7 , ;fig. r'a r ,v t , . c i ilikk , loft: /77 ,s; i ••t,,i,..,.,.6,' s ,‘ '‘','‘‘‘ k ,,j '%S'r I ,- "147,7\:--- t A ,s. , ,,, / ,- ‘ u k..., /,N. o W / �., M -...JAB --------------- rg s B E 1010 EAST HYMAN AVENUE a s $„ 10 0 10 20 APPROXIMATE SCALE—FEET 'C' "�� o: AED 4 03/01/2023 EQ 21 -7-655 Kumar & Associates LOCATION OF EXPLORATORY BORING rig. 1 fj A' ASPEN BUILDING DEPARTMENT BORING 1 LEGEND EL. 7942' FILL: SAND, CLAYEY TO SILTY WITH GRAVEL AND SCATTERED COBBLES AND ORGANICS, LOOSE TO MEDIUM DENSE, MOIST, 0 DARK BROWN, BROWN, LIGHT TO MEDIUM GRAY—TAN. • 5/12 SAND (SP—SM), FINE TO MEDIUM—GRAINED, CLEAN TO SILTY, ♦ WC=8.0 MEDIUM DENSE, MOIST, TAN TO LIGHT GRAYISH—TAN. ♦ +4=22 —200=25 ♦ DRIVE SAMPLE, 1 3/8—INCH I.D. SPLIT SPOON STANDARD ♦ PENETRATION TEST. 5 ' ♦ 12/12 5/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 5 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED♦ TO DRIVE THE SAMPLER 12 INCHES. ♦ •— = 10 ♦ NOTES 13/12 0_— 1. THE EXPLORATORY BORING WAS DRILLED ON AUGUST 13, 2021 WITH A 4—INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 15 122/12 3. THE ELEVATION OF THE EXPLORATORY BORING WAS OBTAINED WC=4.2 BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN +4=0 PROVIDED. —200=14 4. THE EXPLORATORY BORING LOCATION AND ELEVATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY 20 THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 6913); —200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). r 3 I I e E a E1 21 -7-655 Kumar &Associates LOG OF EXPLORATORY BORING ' 0 3% 1/2023 ASPEN BUILDING DEPARTMENT HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 HRS ioo 45 MIN 15 MIN 6OMIN 19MIN 4MIN 1MIN #200 #100 #50#40#30 #16 #10#8 #4 3/8" 3/4" 1 1/2" 3" 5"6" 8"0 90 10 80 20 70 30 60 40 rn 50 50 E : EI a 40 60 ' 30 70 20 80 10 90 0 I I I I I I I I I I I I III I I 1 1 1 1 I I I I I I I III I I I I I I III 100 .001 .002 .005 .009 .019 .037 .075 .150 .300 .600 1.18 2.36 4.75 9.5 19 38.1 76.2 127 200 .425 2.0 152 I DIAMETER OF PARTICLES IN MILLIMETERS CLAY TO SILT SAND GRAVEL COBBLES FINE MEDIUM COARSE FINE COARSE GRAVEL 22 % SAND 53 % SILT AND CLAY 25 % LIQUID LIMIT — PLASTICITY INDEX — SAMPLE OF: Gravelly Clayey Sand (Fill) FROM: Boring 1 0 2.5' HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 24 HRS 7 HRS 100 45 MIN 15 MIN 60MIN 19MIN 4MIN 1MIN #200 #100 50#40 30 416 41 lijI8 #4 3/8" 3/4" 1 1/2" 3" 5"6" 8"0 90 10 80 20 70 30 60 40 G v ~ 50 50 40 60 a s 30 70 E S 20 80 10 90 Y0 1 1 I I I I 1 1 I I I I I I I 1 1 1 I I I I 1 I I I I I I I 1 1 1 1 1 1 1 1 1 100 .001 .002 .005 .009 .019 .037 .075 .150 .300 .600 1.18 2.36 4.75 9.5 19 38.1 76.2 127 200 1425 2.0 152 DIAMETER OF PARTICLES IN MILLIMETERS E CLAY TO SILT COBBLES FINE SAND MEDIUM COARSE FINE GRAVEL COBBLES 1 e GRAVEL 0 % SAND 86 % SILT AND CLAY 14 % N LIQUID LIMIT — PLASTICITY INDEX — These test results apply only to the samples which were tested. The 11 SAMPLE OF: Silty Sand FROM: Boring 1 0 15' testing report shall not be reproduced, except In full, without the written 35 approval of Kumar & Associates, Inc. i 7 Sieve analysis testip�(S • accordance with A !.. . ri ASTM C136 and/o it 13 n� II 21 —7-655 Kumar & Associates GRADATION TEST RESULTS 0 /E• �1�2023 e% ASPEN BUILDING DEPARTMENT I( i Kumar&Associates,Inc.° Gumar&Aland Materials Engineers and Environmental Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No.21-7-655 SAMPLE LOCATION NATURAL NATURAL GRADATION ATTERBERG LIMITS UNCONFINED MOISTURE DRY GRAVEL SAND PERCENT PLASTIC COMPRESSIVE BORING DEPTH CONTENT DENSITY (%) (%) PASSING 200 S EVE LIQUID LIMIT INDEX STRENGTH SOIL TYPE (ft) (%) (pcf) (%) (%) (psf) 1 21A 8.0 22 53 25 Gravelly Clayey Sand(Fill) 15 4.2 0 86 14 Silty Sand • • RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT I C A Kumar&Associates,Inc.° Geotechnical and Materials Engineers and Environmental Scientists TABLE 2 PERCOLATION TEST RESULTS PROJECT NO.21-7-655 HOLE NO. HOLE DEPTH LENGTH OF WATER DEPTH WATER DEPTH DROP IN AVERAGE (INCHES) INTERVAL AT START OF AT END OF WATER LEVEL PERCOLATION (MIN) INTERVAL INTERVAL (INCHES) RATE (INCHES) (INCHES) (MIN./INCH) 66 47 19 0.3 47 40 7 0.7 40 35 5 1 B-1 184 5 35 31 4 1.3 31 28 3 1.7 28 25% 2/2 2 Note: The percolation test was conducted in the completed 4-inch diameter borehole at the depth indicated on August 13, 2021. RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT Hydrologic Soil Group—Aspen-Gypsum Area,Colorado,Parts of Eagle,Garfield,and Pitkin Counties N (1010 E Hyman Ave(Aspen,CO)) 343483 343488 343493 343498 343503 343508 343513 39°11'16"N a8 39°11'16"N • 2 2 — qii 1 :-_- ro rn ) ill . 4 i T ( A ,. P 4 =fit 8 0 • •12 • 11111 eVE9 0 11 4 0s U i`rasp may not b- alid .Q Bird 0GaB@° 0 39°11'15"N I I I 39°11'15'N '1444 3 343488 343493 343498 343503 343508 a 3 v Map Scale:1:200 if printed on A portrait(8.5"x 11")sheet. Meteo N 0 2 5 10 15 � Rs.�►1E1VED Feet A0 5 10 20 30 Map projection:Web Mercator Corner coordinates:WGS84 Edge tics:UTM Zone 13N WGS84 0 3/0 1/2 0 2 3 USDA Natural Resources Web Soil Survey 2/8/20 3 ism Conservation Service National Cooperative Soil Survey Page 1 o SPEN BUILDING DEPARTMENT Hydrologic Soil Group—Aspen-Gypsum Area,Colorado,Parts of Eagle,Garfield,and Pitkin Counties (1010 E Hyman Ave(Aspen,CO)) MAP LEGEND MAP INFORMATION Area of Interest(AOI) p c The soil surveys that comprise your AOI were mapped at Area of Interest(AOI) 1:24,000. 0 C/D Soils • D Warning:Soil Map may not be valid at this scale. Soil Rating Polygons 0 A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil n A/D Water Features line placement.The maps do not show the small areas of Streams and Canals contrasting soils that could have been shown at a more detailed �I B scale. Transportation Q B/D *4-4 Rails Please rely on the bar scale on each map sheet for map n C measurements. ti Interstate Highways C/D US Routes Source of Map: Natural Resources Conservation Service Web Soil Survey URL: 0 D Major Roads Coordinate System: Web Mercator(EPSG:3857) n Not rated or not available Local Roads Maps from the Web Soil Survey are based on the Web Mercator Soil Rating Lines projection,which preserves direction and shape but distorts — A Background• distance and area.A projection that preserves area,such as the 1111 Aerial Photography Albers equal-area conic projection,should be used if more ^•• A/D accurate calculations of distance or area are required. "ow B This product is generated from the USDA-NRCS certified data as •Rr B/D of the version date(s)listed below. C Soil Survey Area: Aspen-Gypsum Area,Colorado,Parts of Eagle,Garfield,and Pitkin Counties ",. CID Survey Area Data: Version 13,Sep 7,2022 ,.v D Soil map units are labeled(as space allows)for map scales • • Not rated or not available 1:50,000 or larger. Soil Rating Points Date(s)aerial images were photographed: Sep 5,2021—Sep 7, 2021 O A The orthophoto or other base map on which the soil lines were p A/D compiled and digitized probably differs from the background • B imagery displayed on these maps.As a result,some minor shifting of map unit boundaries may be evident. • B/D RECEIVED 03/01/2023 USDA Natural Resources Web Soil Survey 2/8/202 3 Conservation Service National Cooperative Soil Survey Page 2()ASPEN BUILDING DEPARTMENT Hydrologic Soil Group—Aspen-Gypsum Area,Colorado,Parts of Eagle,Garfield,and Pitkin 1010 E Hyman Ave(Aspen,CO) Counties Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 107 Uracca, moist-Mergel B 0.1 100.0% complex, 1 to 6 percent slopes, extremely s Totals for Area of Interest 0.1 100.0% 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. Rating Options Aggregation Method: Dominant Condition RECEIVED USDA Natural Resources Web Soil Survey 2/8/2023 Conservation Service National Cooperative Soil Survey 0 3/O4e/2f02 3 ASPEN BUILDING DEPARTMENT Hydrologic Soil Group—Aspen-Gypsum Area,Colorado,Parts of Eagle,Garfield,and Pitkin 1010 E Hyman Ave(Aspen,CO) Counties Component Percent Cutoff.None Specified Tie-break Rule: Higher USDA Natural Resources Web Soil Survey 2/8/2023 Conservation Service National Cooperative Soil Survey 0 3/03W2f02 3 ASPEN BUILDING DEPARTMENT APPENDIX B URMP Calculations 1. Detention Storage Calculations 2. Percolation Area Calculations 3. Rational Method Runoff Coefficients 4. 100-Year Peak Flow and Pipe Capacity Check RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT RIVERCITY CONSULTANTS 1010 Hyman Ave. Stormwater Calculations Impervious Areas (Square Feet) Existing Proposed 44 Dumpster/AC Pad 1326 Roof Area 1326 Roof Area 489 Back Drive and Stair 489 Back Drive and Stain 237 Ex. Walkway 212 Prop. Walk and Side Stair 87.5 Window Wells 54 Prop. Walk to Rear 2140 Total impervious across entire site 35.4 Window Wells 2160 Total impervious across entire site 100-Yr Detention Volume = 100-Yr 1-hr Storm * Impervious Area of Site 1.23 in 100-Yr 1-hr depth for Aspen 0.103 ft convert rainfall depth to feet 2160 sf Impervious Area -Whole Site V-100 Detention 221.4 cubic ft Required for 100-Yr detention Dry Well Ht 8.8 ft riser barrel and percolation barrel Dry Well Radius 3.5 ft Dry Well Volume 338.7 cubic ft provided RECEIVED RIVER CITY CONSULTANTS,INC•215 PITKIN AVE,UNIT 201•GRAND JUNCTION,COLORADO 81501•970.241.4772 c /0 1/2 0 2 3 S:\PROJECTS\2008 Monique Agnew Architecture\001 1010 Hyman\Design\Drainage\04-Spreadsheets\2008-001 SWMM Spreadsheets.xlsx Detention 1:23 PM,2/AgftN BUILDING DEPARTMENT RIVERCITY CONSULTANTS 1010 Hyman Ave. Stormwater Calculations Area shall be calculated using the following equation: AP = (Vr)/(K)(43.200) Where: AP= Total area of the sides of the percolation area, square feet Vr= Runoff volume. cubic feet K = Hydraulic conductivity of soil. feet/second based off the most conservative percolation or hydraulic conductivity test results provided by a certified geotechnical engineer. Vr = 221.4 cubic ft K = 0.0007 ft/sec (0.5 in/min)*(ft/12 in)*(min/60 sec) AP = 7.38 square feet of percoaltion area required Area of circle = (pi)* (radius^2) 1) Area of 7-ft diameter dry well (w/8"thick walls) 54.54 sq ft [pi*(3.5+(8/12))^2] 2) Area of 18" of stone wrapping primary drywell 100.88 sq ft [pi*(3.5+(8/12)+1.5)^2] 3) Area of foundation dry well stone overlapping primary dry well stone 9.26 sq ft Quantity pulled from AutoCAD 4) Half of dry well perc area that faces West Prop. line 23.17 sq ft [100.88-54.54)/2] Percolation area provided 13.91 sq ft [100.88-54.54-9.26-23.17]sq ft Percolation Area provided is greater than percolation area required RECEIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501•970.241.472.2 c /01/2 0 2 3 S:\PROJECTS\2008 Monique Agnew Architecture\001 1010 Hyman\Design\Drainage\04-Spreadsheets\2008-001 SWMM Spreadsheets.xlsx Percolation Area 11:41 AM,2/2 � Liy BUILDING DEPARTMENT RIVERCITY CONSULTANTS 1010 Hyman Ave. Rational Coefficient Calculations Composite Runoff Coefficients (Whole Site) CcD=K0D+(0.858*i3-0.786*i2+0.774*i+0.04) Where: CA=KA+(1.31*i3-1.44*i2+1.135*i-0.12) CcD=Runoff coefficient for C and D soils CB=(CA+CCD)/2 CA=Runoff coefficients for A soils CB=Runoff coefficients for B soils i=%impervious(asphalt,concrete,etc.)decimal Kco=Coefficient adjustment for C and D soils KA=Coefficient adjustment for A soils ADJUSTMENT FACTORS FOR RUNOFF EQUATIONS 2 YEAR 5 YEAR 10 YEAR 25 YEAR 100 YEAR KCD 0 -0.10*i+0.11 -0.18*i+0.21 -0.28*i+0.33 -0.39*i+0.46 KA 0 -0.08*i+0.09 -0.14*i+0.17 -0.19*i+0.24 -0.25*i+0.32 Impervious Area Area Description 0.050 Impervious(asphalt,concrete,etc.) 0.069 Total area 0.72 !Impervious(i)as decimal 2 Year Runoff Coefficients 25 Year Runoff Coefficients CcD= 0.51 CcD= 0.64 CA= 0.44 CA= 0.54 CB= 0.48 CB= 0.59 5 Year Runoff Coefficients 100 Year Runoff Coefficients CcD= 0.55 CcD= 0.69 CA= 0.47 CA= 0.58 CB= 0.51 CB= 0.63 10 Year Runoff Coefficients CcD= 0.59 CA= 0.51 CB= 0.55 Soil Type for project=TYPE B C2 YEAR C5 YEAR C10 YEAR C25 YEAR C100 YEAR 0.48 0.51 0.55 0.59 0.63 RECEIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501■970.241.47; c /01/2 0 2 3 S:\PROJECTS\2008 Monique Agnew Architecture\001 1010 Hyman\Design\Drainage\04-Spreadsheets\2008-001 SWMM Spreadsheets.xlsx Runoff Coefficients(new SWMM) 4:44 PM,2 / N BUILDING DEPARTMENT RIVERCITY 1010 Hyman Ave. Proposed Flow Rates 100 Year 1 Hour Storm Proposed Flow (Whole Site; Rational Method) I= (a*P1) / (10+Tc)b I= 6.33 I= Average Rainfall Intensity(in/hr) (URMP Eq 2-1) a= 88.8 Constant specific to Aspen,CO(URMP Eq 2-1) P1 = 1.23 Point rainfall value for 100yr/1-hr(in) (URMP Tbl 2.2) Tc= to+tt Time of Concentration(min) Td= 5.00 Lower of Tc or TR(5 minutes minimum) b= 1.052 Constant specific to Aspen,CO QP P100= C*I*A Qp = Peak Flow (cfs) (100 year Proposed) QP r1oo= 0.28 I C= Rational Coefficent(see "Runoff Coefficients") CP100= 0.63 I= 6.33 Average Rainfall Intensity(in/hr) (URMP Eq 2-1) A= 0.069 Contibuting Area(acres) Calculated as above 2-yr 5-yr 10-yr ' 25-yr 100-yr' P1 0.47 0.64 0.77 0.95 1.23 I 2.42 3.29 ' 3.96 ' 4.89 6.33 I CP 0.48 0.51 0.55 0.59 0.63 Qp 0.08 0.12 0.15 0.20 0.28 Pipe Capacity Check All Storm Drain on pipe is 4"SDR 35 PVC designed to be laid at 1/4"per foot(2.08%) Design Flow (>50% Full) Di (ft) 0. 67 �� r = D/2 h = 2r - y radius (ft) 0.167 Area (ft) 0.07 0 = 2 arccos (r r h l WP (It) 0.74 akiik1/4e � R (ft) 0.10 _ _ r2(0 - sine) S (ft/ft) 0.0208 - A r� 2 n (coeff_) 0.009 K (constant) 1.49 P = 27rr - r0 O (rads) 1.85 h (ft) 0.067 Rh = A/P % Full 0.80 Figure 2. Partially Full Pipe Flow Qign. cfs 0.39 Parameters (more than half full) QP1oo• cfs 0.28 °Design, CfS > Qp100, cfs Pipe design capacity at 80% full can accommodate the site's 100-Year Peak Flow RECEIVED RIVER CITY CONSULTANTS,INC■215 PITKIN AVE,UNIT 201■GRAND JUNCTION,COLORADO 81501■970.241.477: c /01/2 02 3 S:\PROJECTS\2008 Monique Agnew Architecture\001 1010 Hyman\Design\Drainage\04-Spreadsheets\2008-001 SWMM Spreadsheets.xlsx Proposed Q 4:44 PM,2/i/gN BUILDING DEPARTMENT APPENDIX C Operation and Maintenance Agreement RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT STORMWATER BEST MANAGEMENT PRACTICES OPERATIONS AND MAINTENANCE AGREEMENT City of Aspen, Colorado THIS AGREEMENT,ma a and entered into this /l day of_ ,F ,20 23,by and between(Insert Full Name of Owner) .4 dee ;5 e ._ s/ hereinafter called the "Landowner",and the ity of Aspen,Colorado,hereinafter called the"City". WITNESSETH WHEREAS,the Landowner is the owner of certain real property described as(Pitkin County tax Map/Parcel Identification Number) 21 3'1 1 i314 n ® 2 located at P/P J'T 04100.0 Ali ,yi fe,✓ Gip/v�;�-�.a .and as more fully as follows,to wit: also known as, ,hereinafter called the"Property";and WHEREAS,the Landowner is proceeding to build on and develop the property;and WHEREAS,the stormwater management BMP Operations and Maintenance Plan for the property identified herein has been approved by the City,herein after called the"Plan",which is attached hereto as Appendix A and made part hereof,as approved by the City,provides for management of stormwater within the confines of the Property through the use of stormwater management or Best Management Practices(BMPs)facilities;and WHEREAS,the City and the Landowner,its successors and assigns,agree that the health,safety,and welfare of the residents of City of Aspen,Colorado and the maintenance of water quality require that on-site stormwater management/BMP facilities be constructed and maintained on the Property;and WHEREAS,the City requires,through implementation of the Plan from the Landowners dated D i r I a and attached hereto,that on-site stormwater management/BMPs as shown on the Plan be ade uat ly constructed,operated,and maintained by the Landowner,its successors and assigns. NOW,THEREFORE,in consideration of the foregoing premises,the mutual covenants contained herein, and the following terms and conditions,the parties hereto agree as follows: 1.Construction of BMP facility by Landowner.The on-site stormwater management/BMP facilities shall be constructed by the Landowner,its successors and assigns,in accordance with the plans and specifications approved by the City and identified in the Plan. 2.Duty of Operation and Maintenance of Facility.The Landowner,its successors and assigns,including any homeowners association,shall adequately operate,inspect,and maintain the stormwater management/BMP facilities as acceptable to the City and in accordance with the specific operation,inspection,and maintenance requirements noted in the Plan. Adequate operation and maintenance is herein defined as good working condition so that these facilities are performing their design functions. 0 3/01/2 0 2 3 ASPEN BUILDING DEPARTMENT 3.Duty of Documentation. The Landowner,its successors and assigns,shall document inspections,maintenance, and repairs performed and provide said documentation to the City or its representatives upon request. 4.Right of Entry on Property. The Landowner,its successors and assigns,hereby grant permission to the City, its authorized agents and employees,to enter upon the Property at reasonable times and upon presentation of proper identification,and to inspect the stormwater management/BMP facilities whenever the City deems necessary.The purpose of inspection is to follow-up on suspected or reported deficiencies,to respond to citizen complaints,and/or to assure safe and proper functioning of the facilities.The City shall provide the Landowner, its successors and assigns,copies of the inspection findings and a directive with timeline to commence with the repairs if necessary. 5.Failure to Maintain. In the event the Landowner,its successors and assigns,fails to construct,operate and maintain the stormwater management/BMP facilities in good working condition acceptable to the City,the City,its authorized agents and employees,may enter upon the Property and take whatever action(s)deemed necessary to correct deficiencies identified in the inspection report and to charge the costs of such construction or repairs to the Landowner.It is expressly understood and agreed that the City is under no obligation to install, construct,or routinely maintain or repair said stormwater management/BMP facilities,and in no event shall this Agreement be construed to impose any such obligation on the City. 6.Reimbursement by Landowner.In the event the City pursuant to this Agreement,performs work of any nature, or expends any funds in performance of said work for labor,use of equipment,supplies,materials,and the like, the Landowner,its successors or assigns,shall reimburse the City upon demand,within thirty(30)days of receipt thereof for all actual costs incurred by the City hereunder. 7.Duty to Inspect by City.The City,its employees or representatives,shall inspect the stormwater management/BMP facilities at a minimum of once every three years to ensure their continued and adequate functioning. 8.Release of City. The Landowner,its executors,administrators,assigns,and other successors in interests,shall release the City,its employees and designated representatives from all damages,accidents,casualties, occurrences,or claims which might arise or be asserted against said City,employees,and representatives from the construction,presence,existence,operative or maintenance of the stormwater management/BMP facilities by the Landowner or City. In the event that a claim is asserted against the City,its elected officials,City Officers or employees,the City shall promptly notify the Landowner and the Landowner shall defend,at its own expense,any suit based on the claim. If any judgment or claims against the City's employees or designated representatives shall be allowed,the Landowner shall pay all costs and expenses regarding said judgment or claim. 9.Recording of Agreement running with the Property. This Agreement shall be recorded in the real property records of Pitkin County,Colorado,and shall constitute a covenant running with the Property or land,and shall be binding on the Landowner,its administrators,executors,assigns,heirs and any other successors in interests, in perpetuity. RE ' WED 03/01/2023 ASPEN BUILDING DEPARTMENT IN WITNESS WHEREOF the undersigned have hereunto affixed their signatures as of the date first above written. LANDOWNER: By: Print Name: !L, -C G- State o Colorado) :ss County of Pitkin) The foregoing Agreement was acknowledged before me this IA day of 1AN u P :i ,20_a3, by A I.IGE E..• 5Psn1 AN'OY2ES N Public My Commission Expires: So N a°►t o?O1 "•` •,AL ZA�LAN sNNMoREs a __� i,,� MY coMNMIs$ION r ea 3O7615 EXPIRES:Juno 29,2023 ?' Banded'Mu Noisy Pubic(Aidenwd er$ THE CITY OF ASPEN: By:J Print Name: State of Colorado) :ss County of Pitkin) The foregoing Agreement was acknowledged before me this day of ,20 , by Notary Public My Commission Expires: RECEIVED 03/01/2023 ASPEN BUILDING DEPARTMENT