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File Documents.230 E Hopkins Ave.0089.2018 (13).ACBK
MOUNTAIN FORGE RENOVATION AND ADDITION PARCEL NO. 273707328008 230-234 EAST HOPKINS AVENUE & 117 SOUTH MONARCH STREET ASPEN (PITKIN COUNTY), COLORADO DRAINAGE REPORT Report Date / History: July 26, 2018 / Initial Permit Submittal January 23, 2019 / Permit Resubmittal August 14, 2019 / Permit Resubmittal Owner: Developer: 360 Hexagon 360 Hexagon Attn: Peter Gluck Attn: Peter Gluck 119 Hyslop Road Brookline, MA 02445 119 Hyslop Road Brookline, MA 02445 Phone: 617-913-2903 Phone: 617-913-2903 Email: pgluck@hexagon-properties.com Email: pgluck@hexagon-properties.com Prepared by: Yarnell Consulting & Civil Design P.O. Box 3901 Eagle, Colorado 81631 229 Midland Avenue Basalt, Colorado Phone: (970) 323-7008 Engineer-of-Record: Justin Yarnell, PE (CO), President Email: Justin@TheYarnells.com 08/14/2019 08/14/2019 Reviewed by Engineering 08/23/2019 3:33:17 PM "It should be known that this review shall not relieve the applicant of their responsibility to comply with the requirements of the City of Aspen. The review and approval by the City is offered only to assist the applicant's understanding of the applicable Engineering requirements." The issuance of a permit based 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. YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page i TABLE OF CONTENTS Table of Contents ................................................................................................................................................... i Appendices .............................................................................................................................................................. ii Engineer’s Certification ...................................................................................................................................... 1 1. General Location and Description ......................................................................................................... 2 1.1. Location ........................................................................................................................................ 2 1.2. Description of Property .............................................................................................................. 2 1.3. Description of Project ................................................................................................................. 2 1.4. Previous Drainage Studies .......................................................................................................... 3 1.5. Adjacent Drainage Issues ............................................................................................................ 3 1.6. Major Drainageway Planning Studies ........................................................................................ 3 1.7. Site Constraints ............................................................................................................................ 3 1.8. Irrigation Facilities ...................................................................................................................... 4 1.9. Drainage Easements / Tracts ..................................................................................................... 4 2. Drainage Basins and Sub-Basins ............................................................................................................ 5 2.1. Major Basin Description ............................................................................................................. 5 2.2. Existing Sub-Basin Description .................................................................................................. 5 2.3. Proposed Sub-Basin Description ................................................................................................ 5 3. Low Impact Site Design .............................................................................................................................. 7 4. Hydrologic Criteria ...................................................................................................................................... 8 4.1. Storm Recurrence Intervals ........................................................................................................ 8 4.2. Design Rainfall ............................................................................................................................. 8 4.3. Runoff Calculation Method ......................................................................................................... 8 4.4. Detention Discharge and Storage Calculation Method ............................................................. 8 4.5. Other Criteria ............................................................................................................................... 8 4.6. Sub-Basin Data ............................................................................................................................. 8 4.7. Existing (Pre-Redeveloped) Runoff ........................................................................................... 9 4.8. Proposed (Post-Redeveloped) Runoff ....................................................................................... 9 4.9. Water Quality Capture Volume and Runoff ............................................................................. 10 4.1. Hydrographs .............................................................................................................................. 10 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page ii 5. Hydraulic Criteria ...................................................................................................................................... 11 5.1. Design Point for Closed Systems .............................................................................................. 11 5.2. Flow Capacity of Drainage Facilities ........................................................................................ 11 5.3. Culvert Design............................................................................................................................ 11 5.4. Storm System Design ................................................................................................................ 11 5.5. Gutter Design ............................................................................................................................. 11 5.6. Inlet Design ................................................................................................................................ 11 5.7. Open Channel Design ................................................................................................................ 12 5.8. Check / Channel Drop Design ................................................................................................... 12 5.9. Downstream / Outfall System Capacity ................................................................................... 12 6. Proposed Drainage Facility Design .................................................................................................... 13 6.1. General Concept......................................................................................................................... 13 6.2. Water Quality Best Management Practices Design ................................................................. 13 6.3. Detention and Outlet Design .................................................................................................... 13 6.4. Drainage Easements / Tracts ................................................................................................... 13 6.5. Off-Site Drainage Facilities ....................................................................................................... 13 6.6. Maintenance ............................................................................................................................... 13 7. Conclusions .................................................................................................................................................. 15 8. References .................................................................................................................................................... 16 APPENDICES Maps ........................................................................................................................................................................... A Hydrologic Calculations ...................................................................................................................................... B Hydraulic Calculations ........................................................................................................................................ C Referenced Reports .............................................................................................................................................. D 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page i 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 1 ENGINEER’S CERTIFICATION I hereby affirm that this report and the accompanying plans for the remodel of 230-234 East Hopkins Avenue and 117 South Monarch Street 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 and 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. SIGNATURE: ________________________________________ Justin J. Yarnell CO PE #47241 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 2 1. GENERAL LOCATION AND DESCRIPTION 1.1. Location The proposed project is located at 230-234 East Hopkins Avenue and 117 South Monarch Street – more specifically Parcel A, 220 East Hopkins Avenue & 230 East Hopkins Avenue / 117 South Monarch Street Minor Subdivision. This is the Mountain Forge building. 1.2. Description of Property Parcel A encompasses a footprint of approximately 6,000 square feet (0.14 acres). It is bounded to the north by a public alley, east by South Monarch Street, south by East Hopkins Avenue, and west by a single-family home. Presently, the site is fully-developed with a commercial structure, recessed courtyard, parking area, minimal landscaping, and utilities. There does not appear to be a lift station on the property; therefore, all drainage that falls into the recessed courtyard is infiltrated. Otherwise, drainage leaves the site in all directions – north, east, south, and west. According to Figure 3.1 of the City of Aspen Urban Runoff Management Plan (URMP), the soils in this part of the city are described as Type B. However, the project’s geotechnical engineer has determined the soils to be Type A; therefore, the drainage calculations will reflect Type A. 1.3. Description of Project It is proposed to extensively renovate the existing building, slightly elevate and improve the recessed courtyard, construct an addition on the rear (north) side of the building, reconstruct the alley immediately adjacent to the property, and construct new utility services for the building. A concrete driveway will connect the alley to a new garage constructed with the addition. The ground cover will remain primarily impervious. Pervious areas will consist primarily of a raised planter along the east side and a partial green roof. In an effort to improve the drainage condition for the recessed courtyard and minimize the risk of flooding the basement level of the building, a new drain basin with backup pump system is proposed. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 3 There is existing barrier curb/gutter along both South Monarch Street and East Hopkins Avenue. In accordance with City Standards, it will be required to reconstruct the sidewalk and curb/gutter within the public right-of-way adjacent to the property. The trees within the right-of-way are slated to remain. 1.4. Previous Drainage Studies The project site is located within the Aspen Mountain Drainage Basin as defined by Figure 1.2 “City of Aspen Drainage Basins” within the URMP. As such, the “Surface Drainage Master Plan for the City of Aspen,” dated November 2001 and prepared by WRC Engineering is applicable to this project site. 1.5. Adjacent Drainage Issues Upon review of the topographic survey for the project, completed by Peak Surveying, the existing topography for the alley is not optimal for drainage conveyance. As opposed to an inverted crown that directs water to the center of the alley, it appears that drainage is directed toward the building located north of the alley. It is proposed to mitigate this as part of the partial alley reconstruction. 1.6. Major Drainageway Planning Studies This project site is not within or immediately adjacent to any major drainageways; therefore, is not subject to any major drainageway planning studies. 1.7. Site Constraints Elevationally, the recessed courtyard sits well below the adjacent rights-of-way. Therefore, there is no option for a gravity-fed overflow path. Alternatively, while it is permissible to infiltrate low-flow events into the soils, mechanical means will be necessary to facilitate removal of large storm events from the courtyard. City Standards require finished floor elevations for new construction be at least 12 inches above the flowline for the curb/gutter to protect buildings from flooding. Fortunately, the concrete walls surrounding the courtyard appear to extend above grade to at least 12 inches above the flowline. This should help keep the courtyard and basement levels from receiving off-site runoff during large storm events. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 4 1.8. Irrigation Facilities There are no known irrigation facilities on or immediately adjacent to the project site that would impact or be impacted by this project. 1.9. Drainage Easements / Tracts Based on the topographic survey prepared by Peak Surveying, there are no existing drainage easements or tracts on the project site. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 5 2. DRAINAGE BASINS AND SUB-BASINS 2.1. Major Basin Description The project site is located within the Aspen Mountain Drainage Basin as defined by Figure 1.2 “City of Aspen Drainage Basins” within the URMP. As such, the “Surface Drainage Master Plan for the City of Aspen,” dated November 2001 and prepared by WRC Engineering is applicable to this project site. 2.2. Existing Sub-Basin Description Based on the topographic survey by Peak Surveying and site reconnaissance by YCCD, the existing sub-basin appears limited to the existing, 0.14-acre parcel with its associated structure, parking, courtyard, and landscaping. There does not appear to be off-site drainage directed onto the site. According to the URMP, the storm sewer system within Aspen Mountain Drainage Basin has adequate capacity to convey the 10-year storm event while the 100-year runoff is contained within the public rights-of-way. Presently, runoff from the subject property appears to be overland in all directions – north, east, south, and west. However, runoff generated within the recessed courtyard appears to infiltrate into the Type A soils found on this site as no gravity or mechanical overflow is provided. Since there is no runoff from the existing site and no detention is required within the Aspen Mountain Drainage Basin, a Drainage Plan for the existing conditions was not developed to accompany this report. 2.3. Proposed Sub-Basin Description It is proposed to improve the existing drainage condition and bring it up to current City Standards with this project. As shown on Drainage Plan Sheet C5.2, sub-basin PR1 consists of the entire roof for both the existing building and the addition. It is approximately 0.11 acres in area and 88% impervious. Although primarily impervious, this sub-basin does include some areas of 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 6 green roof and a proposed, raised planter along the east side of the building. All drainage from the roof is collected and routed to Design Point A along the east side of the building where it is captured by said planter to facilitate water quality improvements. Approximately 0.01 acres in area and 100% impervious, sub-basin PR2 consists of the recessed courtyard. Drainage is captured in a series of small inlets with interconnected, below-grade, gravity-fed piping. Low-flow storm events are proposed to infiltrate into the sub-soils via a new drain basin (with its invert located more than five [5] feet below the basement slab elevation so as not to impact said basement) at Design Point B while storm events that generate more runoff than can be readily infiltrated will be pumped out of the courtyard and discharge into the proposed raised planter east of the building. Approximately 0.01 acres in area and 100% impervious, sub-basin PR3 consists of the side and rear setback areas that cannot, due to numerous site and topographic constraints, be captured but flow into the adjacent rights-of-way and along historic drainage paths toward Design Point C. Since the alley behind the subject property must be repaved to facilitate utility construction, it is proposed to reconstruct it with a central flowline. This should help control flooding for both adjacent properties and keep runoff within the public right-of- way. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 7 3. LOW IMPACT SITE DESIGN Due to the tight nature of this site and the fact that a majority of it will remain impervious, it is challenging to incorporate low impact sign design practices. In an effort to reduce impervious roof area, approximately 301 square feet of green roof is proposed. Furthermore, all roof and courtyard drainage is directed into a proposed raised planter at Design Point A along the east side of the building. The planter is intended to facilitate detention of the water quality capture volume for the entire site – over-sized to account for sub-basin PR3 which cannot be captured. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 8 4. HYDROLOGIC CRITERIA 4.1. Storm Recurrence Intervals In accordance with the URMP, the 10-year and 100-year storm events have been studied as the minor and major storm events, respectively. 4.2. Design Rainfall In accordance with Table 2.3 “Two-Hour Incremental Rainfall Depths for Aspen,” the hydrologic calculations utilize a 10-year, 1-hour precipitation depth of 0.77 inches and a 100-year, 1-hour precipitation depth of 1.23 inches. 4.3. Runoff Calculation Method In accordance with Section 3.3 of the URMP, the Rational Method was used to estimate peak flows from this watershed since the area is less than 90 acres. 4.4. Detention Discharge and Storage Calculation Method In accordance with the requirements of the URMP, the public right-of-way has capacity to handle drainage from any redevelopment within the Aspen Mountain Drainage Basin; therefore, no on-site stormwater detention is required. 4.5. Other Criteria There are no other hydrologic calculation methods that have been used within this analysis that have not been presented in or referenced by the URMP. 4.6. Sub-Basin Data Refer to Appendix B for a tabulation of the area, storm frequency, rainfall intensity, and runoff coefficients for each sub-basin. Due to the small nature of the site and the extensive impervious area, the time of concentration has been estimated as the minimum five (5) minutes for each sub-basin; therefore, these calculations have been omitted from Appendix B. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 9 4.7. Existing (Pre-Redeveloped) Runoff Since no detention is required within the Aspen Mountain Drainage Basin, a Drainage Plan and supporting calculations for the existing condition was not developed to accompany this report. 4.8. Proposed (Post-Redeveloped) Runoff Appendix B contains the hydrologic calculations for the estimated, proposed runoff rates. A summary is included below as Table 1. Table 1: Estimated, Proposed Runoff Rates Sub-Basin Est. 10-year Runoff (CFS) Est. 100-year Runoff (CFS) PR1 0.33 0.55 PR2 0.05 0.08 PR3 0.05 0.08 The proposed drainage condition is anticipated to be improved as a result of this project. First, a majority of the impervious parking area north of the building will no longer be tributary to the alley but be captured as roof drainage and routed east. This should decrease flow into the alley and improve the existing condition. Second, a mechanical overflow (pump) is proposed to lift drainage from high-flow storm events that collect in the courtyard. This will marginally increase the drainage tributary to South Monarch Street. However, according to the URMP, the storm sewer system within Aspen Mountain Drainage Basin has adequate capacity to convey the 10-year storm event while the 100-year runoff is contained within the public rights-of-way. Incorporation of a drain basin with perforations in close proximity to a building foundation is not optimal. However, the project’s geotechnical engineer has reviewed the existing soil conditions and provided parameters for safe construction of a drain basin with perforations in close proximity to the building. The parameters have been incorporated into the proposed design of the system. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 10 4.9. Water Quality Capture Volume and Runoff Appendix C includes a table with the water quality capture volume calculations broken down by sub-basin. The calculations include 315 square feet of coniferous tree canopy and 565 square feet of deciduous tree canopy for the mature trees slated to remain within the right-of-way immediately adjacent to the site. Runoff generated within sub-basins PR1 and PR2 are tributary to a proposed, raised planter east of the building. Although sub-basin PR3 cannot be captured and routed to a viable water quality improvement feature, the raised planter is proposed to be over-sized to also include sufficient volume for PR3. As shown within Appendix C, a WQCV of 90 cubic feet is required (and provided) for these three (3) sub-basins. The planter will be sized to accommodate the required water quality capture volume between the surface of the growth media and the top of the planter. Volumes at or below this quantity are proposed to infiltrate and be absorbed by the growth media. Once saturated, water that reaches the bottom of the media will leave the east side of the planter onto a gravel layer via a series of weep holes at-grade. Events that exceed the available capacity of the planter will flow over the east side as a sharp-crested weir and along historic drainage paths into South Monarch Street. Discharge of the raised planter onto hardscape is not an optimal scenario. As such, a series of options were evaluated and discussed with City Engineering. It was determined that the currently-proposed approach was optimal. Fortunately, precipitation events that will generate sufficient volume to overcome the planter are unlikely to occur during freezing temperatures; therefore, icing of the sidewalk as a result of this design are not anticipated to be a regular occurrence. 4.1. Hydrographs Hydrographs are not applicable to this project. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 11 5. HYDRAULIC CRITERIA 5.1. Design Point for Closed Systems There are no closed systems tied to the city’s existing collection system. 5.2. Flow Capacity of Drainage Facilities Proposed inlets, pipes, and swales have been sized to capture and convey the estimated 100-year tributary flow rate. Further analysis and discussion for each is included in the subsequent sections. 5.3. Culvert Design No culverts are proposed as part of this project. 5.4. Storm System Design There is just one (1), small, gravity-fed, storm system proposed to convey site drainage on this project – a series of 4-inch PVC pipes at 1.0% within the recessed courtyard (sub-basin PR2). The pipe capacity calculations within Appendix C indicate this pipe has an 80% capacity of approximately 0.20 CFS – well above the estimated 100-year runoff rate of 0.08 CFS for that entire sub-basin – without surcharging. 5.5. Gutter Design The only gutters proposed for this project will merely be a removal and replacement of those which already exist along South Monarch Street and East Hopkins Avenue. It is assumed analysis of these gutters was completed during evaluation of the entire Aspen Mountain Drainage Basin by WRC Engineering; therefore, has not been completed as part of this project. 5.6. Inlet Design There are just four (4) inlets proposed within the recessed courtyard as part of this project. Splitting the already low estimated 100-year flow rate of 0.08 CFS for the entire sub-basin into the four (4) inlets results in a need for each inlet to accept just 0.02 CFS. This flow rate is so low that essentially zero (0) head is required over the inlet grates. An inlet capacity chart is included within Appendix C. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 12 5.7. Open Channel Design There are no open channels associated with this project. 5.8. Check / Channel Drop Design There are no check / channel drops associated with this project. 5.9. Downstream / Outfall System Capacity All drainage from this site is tributary to public right-of-way. According to the URMP, the storm sewer system within Aspen Mountain Drainage Basin has adequate capacity to convey the 10-year storm event while the 100-year runoff is contained within the public rights-of-way. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 13 6. PROPOSED DRAINAGE FACILITY DESIGN 6.1. General Concept In general, it is proposed to improve the existing drainage condition with this project. 6.2. Water Quality Best Management Practices Design Runoff generated within sub-basins PR1 and PR2 are tributary to a proposed, raised planter east of the building. Although sub-basin PR3 cannot be captured and routed to a viable water quality improvement feature, the raised planter is proposed to be over-sized to also include sufficient volume for PR3. As shown within Appendix C, a WQCV of 90 cubic feet is required (and provided) for these three (3) sub-basins. 6.3. Detention and Outlet Design No detention is required for this project. As such, there is no outlet design required. 6.4. Drainage Easements / Tracts There are no existing or proposed drainage easements or tracts associated with this project. 6.5. Off-Site Drainage Facilities All drainage from this site appears tributary to public right-of-way which is needed to safely convey runoff to the Roaring Fork River. According to the URMP, the storm sewer system within Aspen Mountain Drainage Basin has adequate capacity to convey the 10- year storm event while the 100-year runoff is contained within the public rights-of-way. 6.6. Maintenance Maintenance associated with the storm water infrastructure of the project generally requires that built-up sediment be removed from the raised planter, inlets, and pipe. Second, if deemed to be functioning deficiently, the drain basin with perforations may require removal and replacement every five (5) to 10 years. Third, the sump pump shall be inspected, tested, and lubricated as recommended by the manufacturer. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 14 All maintenance shall be done by the owner or his property manager on at least an annual basis. The contact information for the owner can be found on the cover of this report. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 15 7. CONCLUSIONS In conclusion, the drainage design for the proposed renovation of and addition to the Mountain Forge at 230-234 East Hopkins Avenue and 117 South Monarch Street is in full conformance with the City of Aspen URMP. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION Page 16 8. REFERENCES · “Flood Insurance Rate Map Number 08097C0203C.” Federal Emergency Management Agency. 4 June 1987. · Mechling, John. “Geotechnical Investigation, Mountain Forge Renovation and Addition, 230-234 East Hopkins Avenue, Aspen, Colorado.” CTL | Thompson. 04 May 2018. 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION APPENDIX A – MAPS 08/14/2019 © 2018 Microsoft Corporation © 2018 DigitalGlobe ©CNES (2018) Distribution Airbus DS 08/14/2019 PROJECT SITE 08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION APPENDIX B – HYDROLOGIC CALCULATIONS 08/14/2019 230-234 East Hopkins Avenue Project No.:18.006 RATIONAL METHOD DRAINAGE CALCULATIONS Storm Event: Proposed Jurisdiction: City of Aspen 2 5 10 25 100 Soil Type:A C2 C5 C10 C25 C100 Landscape 0.01 0.01 0.01 0.01 0.13 2.0% Roof 0.84 0.86 0.87 0.84 0.89 100.0% Asphalt 0.84 0.86 0.87 0.84 0.89 100.0% Concrete 0.84 0.86 0.87 0.84 0.89 100.0% Gravel 0.84 0.86 0.87 0.84 0.89 100.0% Landscape Roof Asphalt Concrete Gravel PR1 0.11 0.01 0.10 0.74 0.76 0.77 0.74 0.80 88.1% PR2 0.01 0.01 0.84 0.86 0.87 0.84 0.89 100.0% PR3 0.01 0.01 0.84 0.86 0.87 0.84 0.89 100.0% 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 TOTAL 0.14 0.01 0.10 0.00 0.03 0.00 0.76 0.78 0.79 0.76 0.82 90.5% Project Name: P.O. Box 3901 Eagle, Colorado 81631 YARNELL CONSULTING & CIVIL DESIGN, LLC 129 Midland Avenue Basalt, Colorado 81621 (970) 323-7008 1/22/2019 COMPOSITE IMPERVIOUS AREA (ac) SUB- BASIN AREA PER SURFACE CHARACTERISTIC (ac) STORM EVENT: RUNOFF COEFF.: PERCENT IMPERVIOUS SU R F A C E COMPOSITE RUNOFF COEFFICIENTS 08/14/2019 230-234 East Hopkins Avenue Project No.:18.006 RATIONAL METHOD DRAINAGE CALCULATIONS Storm Event: Proposed STANDARD FORM SF-3 (STORM DRAINAGE SYSTEM DESIGN) Return Period: 10-YEAR Rainfall Depth: 0.77 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) PR1 A 0.11 0.77 5.0 0.08 3.96 0.33 PR2 B 0.01 0.87 5.0 0.01 3.96 0.05 PR3 C 0.01 0.87 5.0 0.01 3.96 0.05 *All calculations are per City of Aspen URMP, Chapter 3 P.O. Box 3901 Eagle, Colorado 81631 YARNELL CONSULTING & CIVIL DESIGN, LLC (970) 323-7008 1/22/2019 Project Name: REMARKSAREA (AC) RUNOFF COEFF tc (MIN) 129 Midland Avenue Basalt, Colorado 81621 BASIN DESIGN POINT DIRECT RUNOFF TOTAL RUNOFF tc (MIN) S(CxA) (AC) I (IN/HR) Q (CFS) CxA (AC) I (IN/HR) Q (CFS) 10-YEAR 1/22/2019 9:08 PM D:\Dropbox (Dropbox)\Project Files\18.006-230-234 East Hopkins Avenue, Aspen\Engineering\Drainage\2019.01.XX Permit Resubmittal\Rational Method - Proposed08/14/2019 230-234 East Hopkins Avenue Project No.:18.006 RATIONAL METHOD DRAINAGE CALCULATIONS Storm Event: Proposed STANDARD FORM SF-3 (STORM DRAINAGE SYSTEM DESIGN) Return Period: 100-YEAR Rainfall Depth: 1.23 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) PR1 0.11 0.80 5.0 0.09 6.33 0.55 PR2 0.01 0.89 5.0 0.01 6.33 0.08 PR3 0.01 0.89 5.0 0.01 6.33 0.08 *All calculations are per City of Aspen URMP, Chapter 3 P.O. Box 3901 Eagle, Colorado 81631 YARNELL CONSULTING & CIVIL DESIGN, LLC (970) 323-7008 1/22/2019 Project Name: Q (CFS) BASIN DESIGN POINT 129 Midland Avenue Basalt, Colorado 81621 REMARKSAREA (AC) RUNOFF COEFF tc (MIN) CxA (AC) I (IN/HR) Q (CFS) DIRECT RUNOFF TOTAL RUNOFF tc (MIN) S(CxA) (AC) I (IN/HR) 100-YEAR 1/22/2019 9:08 PM D:\Dropbox (Dropbox)\Project Files\18.006-230-234 East Hopkins Avenue, Aspen\Engineering\Drainage\2019.01.XX Permit Resubmittal\Rational Method - Proposed08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION APPENDIX C – HYDRAULIC CALCULATIONS 08/14/2019 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 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 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 12" Drop In Grate Inlet Capacity Chart 08/14/2019 Project Name:Project No.: 18.004 PIPE CAPACITY CALCULATIONS: MANNING'S EQUATION Solve for… Flow Rate, Q Pipe Type… PVC N-value… 0.010 Slope (ft/ft) = 0.01 Percent Full = 80% Pipe Diameter, Area, A Hydraulic Velocity, v d (in.) (sf) Radius, R (ft) (cfs) (gpm) (fps) 4 0.09 0.08 0.0100 0.20 89 2.3 6 0.20 0.13 0.0100 0.58 262 3.0 8 0.35 0.17 0.0100 1.26 565 3.6 10 0.55 0.21 0.0100 2.28 1025 4.2 12 0.79 0.25 0.0100 3.71 1667 4.7 18 1.77 0.38 0.0100 10.95 4914 6.2 21 2.40 0.44 0.0100 16.51 7412 6.9 24 3.14 0.50 0.0100 23.58 10582 7.5 30 4.91 0.63 0.0100 42.75 19187 8.7 36 7.07 0.75 0.0100 69.52 31200 9.8 42 9.62 0.88 0.0100 104.86 47062 10.9 48 12.56 1.00 0.0100 149.72 67192 11.9 54 15.90 1.13 0.0100 204.96 91987 12.9 60 19.63 1.25 0.0100 271.45 121828 13.8 66 23.75 1.38 0.0100 350.00 157082 14.7 72 28.26 1.50 0.0100 441.41 198105 15.6 230-234 East Hopkins Avenue Slope (ft/ft) Flow Rate, Q P.O. Box 3901 YARNELL CONSULTING & CIVIL DESIGN 229 Midland Avenue Eagle, Colorado 81631 Basalt, Colorado 81621 (970) 323-7008 7/20/2018 08/14/2019 Project Name: 230-234 East Hopkins Avenue Project No.:18.006 WATER QUALITY CAPTURE VOLUME CALCULATIONS (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) PR1 0.109 0.096 315 565 3992 84.1% 0.185 64 PR2 0.014 0.014 606 100.0% 0.255 13 PR3 0.014 0.014 593 100.0% 0.255 13 BASIN TOTAL IMPERVIOUS AREA (AC)CONIFEROUS DECIDUOUS (WATERSHED- INCHES)(CF) YARNELL CONSULTING & CIVIL DESIGN, LLC (970) 323-7008 1/22/2019 *All calculations are per City of Aspen URMP, Chapter 8 TREE CANOPY AREA (SF)EFFECTIVE IMPERVIOUS AREA (SF) TOTAL AREA (AC) EFFECTIVE IMPERVIOUSNESS WQCV REMARKS P.O. Box 3901 Eagle, Colorado 81631 129 Midland Avenue Basalt, Colorado 81621 WQCV 1/22/2019 9:09 PM D:\Dropbox (Dropbox)\Project Files\18.006-230-234 East Hopkins Avenue, Aspen\Engineering\Drainage\2019.01.XX Permit Resubmittal\Rational Method - Proposed08/14/2019 YARNELL CONSULTING & CIVIL DESIGN MOUNTAIN FORGE RENOVATION AND ADDITION APPENDIX D – REFERENCED REPORTS 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019 08/14/2019