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HomeMy WebLinkAboutEAST OAK TOWNHOMES - PDP230018 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT LOTS 1-15 EAST OAK TOWNHOMES SUBDIVISION Prepared for: CCC Development 221 East Oak Street, Unit A Fort Collin, CO 80524 Prepared by: Wilson & Company 4065 St Cloud Drive, Suite 201 Loveland, Colorado 80538 970-834-6364 February 28, 2024 Job Number 22-100-645-00 4065 St. Cloud, Suite.201 Loveland, CO 80538 970-834-6364 phone February 28, 2024 Mr. Stephen Agenbroad City of Fort Collins Stormwater Engineering 700 Wood Street Fort Collins, CO 80522 RE: Preliminary Drainage and Erosion Control Report for Lots 1-15 East Oak Townhomes Subdivision Dear Stephen, I am pleased to submit for your review and approval, this Preliminary Drainage and Erosion Control Report for Lots 1-15 East Oak Townhomes Subdivision development. I certify that this report for the drainage design was prepared in accordance with the criteria in the Fort Collins Stormwater Criteria Manual. City of Fort Collins Concept Review comments dated September 21, 2023 have been addressed in this report. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Abigail Wright, EIT Michael Oberlander, P.E. Civil Engineer in Training Colorado Professional Engineer No. 34288 4065 St. Cloud, Suite.201 Loveland, CO 80538 970-834-6364 phone ENGINEER’S CERTIFICATION “I hereby attest that this report for the final drainage design for the Lots 1-15 East Oak Townhomes Subdivision development was prepared by me or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others.” ____________________________________________ _______________________ Registered Professional Engineer Date Michael Oberlander, PE Registered Professional Engineer State of Colorado No. 34288 For and on behalf of Wilson & Company Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page i Table of Contents 1. GENERAL LOCATION AND DESCRIPTION ................................................................. 1 1.1 Location ........................................................................................................................... 1 1.2 Description of Property and Project............................................................................. 1 1.3 Floodplain Submittal Requirements ............................................................................ 1 2. DRAINAGE BASINS AND SUB-BASINS .......................................................................... 2 2.1 Major Basin Description ................................................................................................ 2 2.2 Sub-basin Description .................................................................................................... 2 3. DRAINAGE DESIGN CRITERIA ....................................................................................... 2 3.1 Regulations ...................................................................................................................... 2 3.2 Directly Connected Impervious Area (DCIA) Discussion .......................................... 2 3.3 Development Criteria Reference and Constraints ...................................................... 3 3.4 Hydrological Criteria ..................................................................................................... 3 3.5 Hydraulic Criteria .......................................................................................................... 6 3.6 Low Impact Development (LID) Conformance .......................................................... 6 3.7 Water Quality (WQ) Treatment Criteria .................................................................... 6 3.8 Detention Requirements ................................................................................................ 7 3.9 Floodplain Regulations Compliance ............................................................................. 7 3.10 Modifications of Criteria ............................................................................................... 7 4. DRAINAGE FACILITY DESIGN ....................................................................................... 7 4.1 General Concept ............................................................................................................. 7 4.2 Specific Details ................................................................................................................ 7 4.3 LID, WQ and Detention ................................................................................................ 9 5. SEDIMENT AND EROSION CONTROL .......................................................................... 9 6. CONCLUSIONS .................................................................................................................. 10 6.1 Compliance with Standards ........................................................................................ 10 6.2 Drainage Concept ......................................................................................................... 11 7. REFERENCES ..................................................................................................................... 11 APPENDIX A VICINITY MAP AND DRAINAGE PLAN....................................................... A APPENDIX B HYDROLOGIC COMPUTATIONS ................................................................... B APPENDIX C HYDRAULIC CALCULATIONS (TO BE COMPLETED AT FINAL)............ C APPENDIX D IMPERVIOUS AREA EXHIBIT AND LID CALCULATIONS ....................... D APPENDIX E SOILS AND FLOODPLAIN INFORMATION .................................................. E Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location Lots 1-15 East Oak Townhomes Subdivision is in the Southwest ¼ of Section 12, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. It is in Old Town Fort Collins and is bounded on the north by Lot 26 (the McIntyre House) of the Original Town Plat, on the east by Mathews Street, on the south by East Oak Street and on the west by an alley and Lots 17 and 18 and the east half of Lots 19-22 of the Original Town. Please refer to the Vicinity Map located in Appendix A. 1.2 Description of Property and Project The project area is 0.48 acres and is currently occupied by Northern Colorado Real Estate Brokers, LLC and the Community of Christ- Fort Collins Congregation. The project proposes to develop a single family attached project including attached 3 story units with associated drive aisle and sidewalk, wet and dry utilities, and alley improvements. Offsite flow does not contribute to the site from any direction. According to Natural Resources Conservation Service Web Soil Survey, the soils onsite consist of Santana loam, 0 to 1 percent slopes, Soil Group C. Please refer to Appendix E for the Hydrologic Soil Group – Larimer County Area map that includes this site. 1.3 Floodplain Submittal Requirements The area is designated as Zone X, Area of Minimal Flood Hazard, on FIRM Panel 08069C0979H, dated 5/02/2012 and is therefore not within any FEMA mapped floodplain. The site does not have any adjacent City of Fort Collins local floodplains. A Floodplain Submittal is not required and has not been included with this report. Please refer to Appendix E for the National Flood Hazard Layer FIRMette. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 2 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description Lots 1-15 East Oak Townhomes Subdivision is part of the Old Town Basin Master Drainage Plan. The basin is in north-central Fort Collins and is urbanized. All the water from the basin drains to the Poudre River located north of the site. 2.2 Sub-basin Description The property is in the north central part of the Old Town Basin and drains to the existing storm system in Mathews and Oak Street. 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the “Fort Collins Stormwater Criteria Manual” (FCSCM) specifications. Where applicable, the criteria established in the Mile High Flood District’s (MHFD) “Urban Storm Drainage Criteria Manual” (USDCM), developed by the Denver Regional Council of Governments, has been used. 3.2 Directly Connected Impervious Area (DCIA) Discussion The USDCM recommends a four-step process for receiving water protection that focuses on reducing runoff volumes, treating the water quality capture volume (WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process applies to the management of smaller, frequently occurring events. Step 1: Employ Runoff Reduction Practices To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact Development (LID) strategies, including Minimizing Directly Connected Impervious Areas (MDCIA). Runoff from the site shall be conveyed to a permanent water quality facility (ADS Stormtech system) which promotes settlement of particles and will slow the "first flush" from all storms entering the public street and storm sewer system. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 3 Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release Runoff from the site shall be conveyed to an underground water quality facility which reduces the rate of runoff and promotes settlement of particles. Step 3: Stabilize Drainageways Natural Drainageways are subject to bed and bank erosion due to increases in frequency, duration, rate, and volume of runoff during and following development. Because the site will drain to an existing storm system, bank stabilization is unnecessary with this project. Step 4: Implement Site Specific and Other Source Control BMPs The proposed project will control pollutants by encouraging them to settle out inside the isolator row of the ADS Stormtech system before being released from the site. The proposed project will proactively control pollutants at their source by preventing pollution rather than removing contaminants once they have entered the stormwater system as compared to historic conditions. 3.3 Development Criteria Reference and Constraints All basins in Fort Collins are required to provide LID water quality. This will be discussed in subsequent sections of the report. The stormwater outfall for this site is the existing public inlet on the southeastern corner of the site and storm system in Oak Street. The Cache la Poudre River is the ultimate outfall. 3.4 Hydrological Criteria The City of Fort Collins requires that all drainage system design and construction take into consideration two design storms: the minor storm and the major storm. The “minor storm” is the 2-year storm or the 50th percentile storm event. The “major storm” is the 100-year storm or the one percentile storm event. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 4 Runoff computations were prepared for the 2-year minor and 100-year major storm frequencies utilizing the Rational Method. The study was divided into five onsite basins that can be identified on the Drainage Plan in Appendix A. Percentage impervious values were based on proposed land surface types and are specified in the following table from the FCSCM. Table 1. Recommended Percentage Imperviousness Values. The runoff coefficients are based on surface type and specified in the following table from the FCSCM. The site is classified as NRCS Hydrologic Soil Group C. Table 2. Surface Type – Runoff Coefficients. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 5 The City of Fort Collins requires a Frequency Adjustment Factor for the 100-year Storm Return Period. The following table lists this factor, Cf. Table 3. Frequency Adjustment Factors. The rainfall intensities used in the Rational Method computation of runoff were obtained from the Fort Collins Rainfall IDF Curve contained in the figure below. Figure 1. Rainfall IDF Curve – Fort Collins. All hydrological calculations including a summary of the calculated minor and major rainfall event flows are provided in Appendix B. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 6 3.5 Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the FCSCM and/or the USDCM. Final hydraulic calculations will be included in future submittals. Preliminary calculations (inlet sizing and StormCAD analysis) are included in Appendix C. 3.6 Low Impact Development (LID) Conformance Integration of LID systems into the drainage design is required for all development projects. The implementation of LID systems requires one of the following two options: 1. 50% of the newly added or modified impervious area must be treated by LID techniques and 25% of new paved (vehicle use) areas must be pervious. 2. 75% of newly added or modified impervious area must be treated by LID techniques. Pervious pavement is not proposed; therefore, 75% of the newly added or modified impervious area must be treated by LID techniques. This is accomplished with an underground water quality treatment system (ADS Stormtech system). For this site, more than 75% is provided in the ADS Stormtech system. The actual treated area at this time is 95% and the remaining 5% of water quality treatment is in the Udall Natural Area regional pond. Please refer to the Impervious Area Exhibit in Appendix D for comparison of the existing and proposed impervious areas. 3.7 Water Quality (WQ) Treatment Criteria The City requires stormwater quality treatment of all new or modified impervious areas. For this site, 25% of the standard water quality requirement is already provided for in the City’s Udall Natural Area water treatment facility. The site will provide water quality for 95% of the newly added or modified impervious area with the LID facility. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 7 3.8 Detention Requirements Because the development is not increasing impervious area greater than 5,000 square feet, detention is not required. The increase in impervious area has been calculated to be 2,735 square feet. 3.9 Floodplain Regulations Compliance The project is not within any FEMA mapped floodplain. Therefore, a Floodplain Submittal is not required and has not been included with this report. 3.10 Modifications of Criteria There are currently zero Modifications of Criteria for this project. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The storm runoff of the proposed development will be conveyed to the Mathews Street curb and gutter in the northeast corner of the site after being treated through the LID system. 95% of the impervious area of the site will pass through a proposed underground water quality treatment system (ADS Stormtech system). Details for LID water quality will continue to be developed as the project design progresses. The Stormtech system will receive the building roof drains and the courtyard / drive area. A weir will be placed downstream of the collection system and Stormtech chambers. In larger events, the weir will overtop into an outlet pipe, concrete channel and new Mathews Street sidewalk culvert system and to the curb of Mathews. 4.2 Specific Details A summary of the drainage patterns within each basin is provided in the following paragraphs. Please refer to Appendix A for the drainage plan. Basin A is 0.29 acres and contains the proposed building. This basin will produce 0.8 cfs and 2.9 cfs during the 2-year and 100-year events, respectively. Roof drains from the west buildings will drain to a 12-inch storm system and roof drains from the east building will drain to a 6-inch system. Both systems will direct the roof flow north to a structure with a sump that will then backwater into the ADS Stormtech system for treatment. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 8 Basin B is 0.17 acres and is located in the center and north side of the site and contains the landscaping and concrete drive between buildings. This basin drains to proposed landscape area inlets located in the landscape areas adjacent to the west building, and to a 24” inch area inlet and a 2’x3’ ADS Nyloplast curb inlet on the north side of the site. The landscape area inlets will drain to the same 12-inch system mentioned in Basin A. The remainder of the basin flow and what is not captured in the landscape inlets will be captured in the 24- inch area inlet and 2’x3’ ADS Nyloplast curb inlet and will drain to the proposed storm system where a weir in the last structure of the storm system will force the flooding of the ADS Stormtech chambers. The treated water from Basins A and B will outlet through the fabric and underdrain of the system. The underdrain will drain to a channel and pipe system under the Mathews sidewalk that will discharge to the curb on Mathews. Basin B will produce 0.4 cfs and 1.6 cfs during the 2-year and 100-year events, respectively. The proposed 2’x3’ ADS Nyloplast inlet will be sized to handle the 100-year flow from both basins A and B. Basin C 0.08 acres and is located west in the alley and south of the building. The basin contains the concrete walk on East Oak Street and a most of the alley west of the site. The basin drains south through the alley and then along the curb and gutter of East Oak Street to an existing storm inlet, design point c. This basin will produce 0.2 cfs and 0.8 cfs during the 2-year and 100-year events, respectively. Basin D is 0.04 acres and contains the north portion of the alley on the west of the development. The basin contains concrete walks and a concrete drive. The basin drains to the center of the alley and continues to drain north as it does today. This basin will produce 0.1 cfs and 0.4 cfs during the 2-year and 100-year events, respectively. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 9 4.3 LID, WQ and Detention The project is required to treat 75% of on-site new impervious area with LID. For this initial submittal, LID treatment has been identified as an underground water quality system (entirely isolator rows of a proposed ADS Stormtech system). The LID will treat 95% of the on-site impervious area. Appendix D includes the Impervious Area Exhibit and preliminary calculations for LID treatment. Table 4. LID Summary Table On-site detention for this site is not required. 5. SEDIMENT AND EROSION CONTROL The disturbed area is less than 1 acre and will not require a State of Colorado Discharge Permit or City of Fort Collins plan and report. Temporary Sediment and Erosion Control Erosion and sedimentation will be controlled on-site during construction by use of vehicle tracking control pad, concrete washout area, silt fence, rock socks in adjacent existing curb and gutter, inlet protection, and seeding and mulch. The measures will be designed to limit the overall sediment yield increase due to construction as required by the City of Fort Collins. During grading, the soil will be roughened and furrowed perpendicular to the prevailing winds. 75% On-Site Treatment by LID Requirement New or Modified Impervious Area 17,428 sf Required Minimum Impervious Area to be Treated 13,071 sf Treatment - ADS Stormtech system 16,503 sf Total impervious Area Treated 16,503 sf Actual % of Impervious Area On-Site Treated by LID 95 % Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 10 During the performance of the work required by these specifications or any operations appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor, equipment, materials, and means required to comply with applicable permits. The Contractor shall carry out proper efficient measures wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing naissance to persons. The Contractor will be held liable for any damage resulting from dust originating from his operations under these specifications on right-of-way or elsewhere. Wherever construction vehicles access routes or intersect paved public roads, provisions must be made to minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. The contractor will be responsible for clearing mud tracked onto city streets daily. All temporary erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. An Erosion Control Plan will be submitted during Final Compliance. 6. CONCLUSIONS 6.1 Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Storm Drainage Design Criteria Manual. Lots 1-15 East Oak Townhomes Subdivision 4065 Saint Cloud Drive; Suite 201, Loveland, CO 80538 phone: 970.834.6364 Page 11 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the preliminary construction plans adequately provide for stormwater quantity and quality treatment of proposed impervious areas. Conveyance elements have been designed to pass required flows and to minimize future maintenance. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 7. REFERENCES 1. City of Fort Collins, “Fort Collins Stormwater Criteria Manual”, adopted December 2018. 2. Mile High Flood District, “Urban Storm Drainage Criteria Manual”, Volume 1 (revised August 2018), Volume 2 (revised September 2017), and Volume 3 (updated January 2021). A APPENDIX A VICINITY MAP AND DRAINAGE PLAN SITE VICINITY MAP SCALE: 1"=500' LOTS 1-15 EAST OAK TOWNHOMES SUBDIVISION EB RD RD SCB W AC SCBRD TEL TEL TEL E SCBSCB RD P E E RD RD SCB G W W W W FI B E R SS SS SS SS SS SS SS SS SS SS SS SS X X X X X X X X X X X X X X X X X X X X X X X X X W W W W W W W W W W W W W W W W W W SS SS SS SS SS SS SS SS SS SS SS SS 4981.5 4 9 8 1 49 7 7 . 5 497 8 4978. 5 49 7 9 4979.5 4979.5 49 8 0 49 8 0 . 5 STORMTECH 160 LP (12X2) MA T H E W S S T R E E T E OAK STREET AL L E Y MCINTYRE HOUSE LOT 26, BLOCK 131 ORIGINAL TOWN GARAGE LOT 1 LOT 2 LOT 3 LOT 4 LOT 5 LOT 6 LOT 7 LOT 8 LOT 9 LOT 10 LOT 11 LOT 15 LOT 14 LOT 13 LOT 12 LOT 17-18, BLOCK 131 ORIGINAL TOWN EAST 1/2 OF LOTS 19-22, BLOCK 131 ORIGINAL TOWN LOT 7-16, BLOCK 131 ORIGINAL TOWN TRACT A UE,DE, PRIVATE AE 4 9 8 1 498 1 . 5 49 8 1 . 5 498 1 . 5 4 9 8 1 . 5 49 8 1 . 5 4981 4980.5 49804981.5 4 9 8 1 . 5 49 8 1 . 5 4979 4978.5 4 9 7 8 . 5 4 9 7 9 4 9 7 9 . 5 49 7 9 . 5 DRAINAGE PLAN 7 MPO AGW MPO 22-100-645-00 FEBRUARY 28, 2024 40 6 5 S A I N T C L O U D D R I V E , S U I T E 2 0 1 LO V E L A N D , C O 8 0 5 3 8 PH O N E : 9 7 0 - 8 3 4 - 6 3 6 4 ww w . w i l s o n c o . c o m DRAWN BY: CHECKED BY: DATE: DE S C R I P T I O N DA T E PR O P E R T Y O W N E R SE A L PR O J E C T N A M E PROJECT NO: DESIGNED BY: SHEET NO: SHEET TITLE RE V . BY EA S T O A K T O W N H O M E S SU B D I V I S I O N PRE L I M I N A R Y S U B M I T T A L NOT F O R CON S T R U C T I O N CC C D E V E L O P M E N T 22 1 E O A K S T . U N I T A FO R T C O L L I N S , C O 8 0 5 2 4 811 EXISTING MAJOR CONTOUR BASIN COEFFICIENT (100-YR) DRAINAGE BASIN AREA DRAINAGE BASIN NUMBER DESIGN POINT PROPOSED DRAINAGE BASIN DIVIDE LINE FLOW PATH LEGEND EXISTING MINOR CONTOUR PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR B APPENDIX B HYDROLOGIC COMPUTATIONS Wilson & Company DRAINAGE SUMMARY TABLE Design Tributary Area C (2 & 10) C (100) tc (2 & 10) tc (100) Q(2)tot Q(10)tot Q(100)tot Sub-basin REMARKS Point (ac) (min) (min) (cfs) (cfs) (cfs) a A 0.29 0.95 1.00 5.0 5.0 0.8 1.3 2.9 Roof drain system to StormTech Chambers b B 0.17 0.76 0.95 5.0 5.0 0.4 0.6 1.6 Inlets to StormTech Chambers c C 0.08 0.83 1.00 5.0 5.0 0.2 0.3 0.8 Alley south to Oak Street inlet d D 0.04 0.95 1.00 5.0 5.0 0.1 0.2 0.4 Alley north to north alley 231128 COFC FLOW.xls Wilson & Company RUNOFF COEFFICIENTS & % IMPERVIOUS LOCATION:East Oak Townhomes PROJECT NO:22-100-645-00 COMPUTATIONS BY:AGW DATE:12/20/2023 Recommended Runoff Coefficients from Table 3.2-2 of City of Fort Collins Stormwater Criteria Manual Recommended % Impervious from Table 4.1-3 of City of Fort Collins Stormwater Criteria Manual Hydrologic Soil Group Type C Runoff % coefficient Impervious C Streets, parking lots (asphalt): 0.95 100 Sidewalks (concrete): 0.95 100 Roofs: 0.95 90 Pavers: 0.50 40 Landscape Areas (Flat slope, clay) : 0.20 2 Landscape Areas (Avg slope, clay) : 0.25 2 SUBBASIN TOTAL TOTAL ROOFS STREETS, PARKING LOTS PAVERS SIDEWALK LANDSCAPE RUNOFF % DESIGNATION AREA AREA (asphalt) (concrete) (Flat slope, clay) COEFF. Impervious REMARKS (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) Existing Ex Site 0.48 20,932 9,905 4,819 0 1,065 5,143 0.77 71 ROW to EX TBC 0.22 9,457 0 3,337 0 1,813 4,307 0.61 55 TOTAL 0.70 30,389 9905 8156 0 2878 9,450 0.72 66 Proposed Site 0.48 20,932 12,532 0 0 6,103 2,297 0.87 83 ROW to EX TBC 0.22 9,457 0 228 0 5,089 4,140 0.62 57 TOTAL 0.70 30,389 12532 228 0 11192 6,437 0.79 75 Area Treated 0.44 19,271 12,532 0 0 5,193 1,547 0.89 86 16,503 sf Impervious area treated Added Impervious Area=2,735SF Equations - Calculated C coefficients & % Impervious are area weighted C = (Ci Ai) / At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At = total area over which C is applicable; the sum of all Ai's 231128 COFC FLOW.xls Wilson & Company RUNOFF COEFFICIENTS & % IMPERVIOUS LOCATION:East Oak Townhomes PROJECT NO:22-100-645-00 COMPUTATIONS BY:AGW DATE:12/20/2022 Recommended Runoff Coefficients from Table 3.2-2 of City of Fort Collins Stormwater Criteria Manual Recommended % Impervious from Table 4.1-3 of City of Fort Collins Stormwater Criteria Manual Hydrologic Soil Group Type C Runoff % coefficient Impervious C Paved Area (asphalt-streets, parking lots): 0.95 100 Concrete (alley and sidewalks): 0.95 100 Roofs: 0.95 90 Gravel or Pavers: 0.50 40 Landscape Areas (Flat slope, clay) : 0.20 2 Landscape Areas (Avg slope, clay) : 0.25 2 SUBBASIN TOTAL TOTAL ROOF PAVED GRAVEL/PAVERS SIDEWALK LANDSCAPE RUNOFF % DESIGNATION AREA AREA AREA AREA AREA AREA AREA COEFF. Impervious REMARKS (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) A 0.29 12,544 12,532 0 0 0 12 0.95 90 B 0.17 7,221 0 0 0 5,370 1,851 0.76 75 C 0.08 3,665 0 0 0 3,077 588 0.83 84 D 0.04 1,674 0 0 0 1,666 8 0.95 100 Equations - Calculated C coefficients & % Impervious are area weighted C = (Ci Ai) / At Equation 5-2 Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At = total area over which C is applicable; the sum of all Ai's 231128 COFC FLOW.xls Wilson & Company STANDARD FORM SF-2 TIME OF CONCENTRATION - 2 and 10 YR LOCATION: East Oak Townhomes PROJECT NO: 22-100-645-00 COMPUTATIONS BY: AGW DATE: 12/20/2023 2 and 10-yr storm Cf = 1.00 from Table RO-12 of City of Fort Collins Stormwater Code, Volume I SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS DATA TIME (ti) (tt) (URBANIZED BASIN) tc DESIGN SUBBASIN(s) Area C Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) a A 0.29 0.95 5 2.0 0.5 0 2.0 0.012 3.8 0.0 0.5 5 10.0 5.0 b B 0.17 0.76 31 1.0 3.6 170 1.7 0.020 2.1 1.4 4.9 201 11.1 5.0 c C 0.08 0.83 17 2.0 1.7 95 1.2 0.012 2.9 0.5 2.2 112 10.6 5.0 d D 0.04 0.95 17 2.0 0.9 56 0.9 0.012 2.5 0.4 1.3 73 10.4 5.0 EQUATIONS:Overland Flow Length tc = ti + tt Equation 5-3 L=200' Max in developed areas L=500' Max in undeveloped areas ti = [1.87 (1.1 - CCf ) L0.5 ] / S Equation 3.3-2 tt = L/(V*60)Equation 5-5 V=1.49/n * R^2/3*S^1/2 Equation 5-4 12611.0079 6103.3 final tc = minimum of ti + tt and urbanized basin check min. tc = 5 min. due to limits of IDF curves 231128 COFC FLOW.xls Wilson & Company STANDARD FORM SF-2 TIME OF CONCENTRATION - 100 YR LOCATION: East Oak Townhomes PROJECT NO: 22-100-645-00 COMPUTATIONS BY: AGW DATE: 12/20/2023 100-yr storm Cf = 1.25 from Table RO-12 of City of Fort Collins Stormwater Code, Volume I SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS DATA TIME (ti) (tt) (URBANIZED BASIN) tc DESIGN SUBBASIN(s) Area C C*Cf Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) a A 0.29 0.95 1.00 5 2.0 0.3 0 2.0 0.012 3.8 0.0 0.3 5 10.0 5.0 b B 0.17 0.76 0.95 31 1.0 1.6 170 1.7 0.02 2.1 1.4 2.9 201 11.1 5.0 c C 0.08 0.83 1.00 17 2.0 0.6 95 1.2 0.012 2.9 0.5 1.2 112 10.6 5.0 d D 0.04 0.95 1.00 17 2.0 0.6 56 0.9 0.012 2.5 0.4 1.0 73 10.4 5.0 EQUATIONS:Overland Flow Length tc = ti + tt Equation 5-3 L=200' Max in developed areas L=500' Max in undeveloped areas ti = [1.87 (1.1 - CCf ) L0.5 ] / S Equation 3.3-2 tt = L/(V*60)Equation 5-5 V=1.49/n * R^2/3*S^1/2 Equation 5-4 final tc = minimum of ti + tt and urbanized basin check 12,611 6,103 min. tc = 5 min. due to limits of IDF curves 231128 COFC FLOW.xls Wilson & Company RATIONAL METHOD PEAK RUNOFF (City of Fort Collins, 2-Yr Storm) LOCATION: East Oak Townhomes PROJECT NO: 22-100-645-00 COMPUTATIONS BY: AGW DATE: 12/20/2023 2 yr storm, Cf = 1.00 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Design Tributary A C Cf tc i Q (2) from Q (2) Q(2)tot Sub-basin Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) a A 0.29 0.95 5.0 2.85 0.8 0.8 b B 0.17 0.76 5.0 2.85 0.4 0.4 c C 0.08 0.83 5.0 2.85 0.2 0.2 d D 0.04 0.95 5.0 2.85 0.1 0.1 Q = Cf C iA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor i = rainfall intensity (in/hr) from City of Fort Collins IDF curve A = drainage area (acres)i = 24.221 / (10+ tc)0.7968 231128 COFC FLOW.xls Wilson & Company RATIONAL METHOD PEAK RUNOFF (City of Fort Collins, 10-Yr Storm) LOCATION: East Oak Townhomes PROJECT NO: 22-100-645-00 COMPUTATIONS BY: AGW DATE: 12/20/2023 10 yr storm, Cf = 1.00 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Design Tributary A C Cf tc i Q (10) from Q (10) Q(10)tot Sub-basin Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) a A 0.29 0.95 5.0 4.87 1.3 1.3 b B 0.17 0.76 5.0 4.87 0.6 0.6 c C 0.08 0.83 5.0 4.87 0.3 0.3 d D 0.04 0.95 5.0 4.87 0.2 0.2 Q = Cf C iA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor i = rainfall intensity (in/hr) from City of Fort Collins IDF curve A = drainage area (acres)i = 41.44 / (10+ tc)0.7974 231128 COFC FLOW.xls Wilson & Company RATIONAL METHOD PEAK RUNOFF (City of Fort Collins, 100-Yr Storm) LOCATION: East Oak Townhomes PROJECT NO: 22-100-645-00 COMPUTATIONS BY: AGW DATE: 12/20/2023 100 yr storm, Cf = 1.25 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Des. Area A C Cf tc i Q (100) from Q (100) Q(100)tot Design Point Design. (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) a A 0.29 1.00 5.0 9.95 2.9 2.9 b B 0.17 0.95 5.0 9.95 1.6 1.6 c C 0.08 1.00 5.0 9.95 0.8 0.8 d D 0.04 1.00 5.0 9.95 0.4 0.4 Q = C iA Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from City of Fort Collins IDF curve A = drainage area (acres)i = 84.682 / (10+ tc)0.7975 231128 COFC FLOW.xls 12611.01 6103.25 City of Fort Collins Stormwater Criteria Manual City of Fort Collins Stormwater Criteria Manual C APPENDIX C HYDRAULIC CALCULATIONS (TO BE COMPLETED AT FINAL) 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 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 2' x 3' Curb Inlet Diagonal Grate Inlet Capacity Chart High Hood Setting (8.47" Curb Setting) Low Hood Setting (4.47" Curb Setting) Mid Hood Setting (6.47" Curb Setting) 9 cfs Capacity of inlet=9 cfs OK, > Q100 Basins A+B=4.5 cfs (if all area inlets were plugged) EB RD RD SCB W AC SCBRD TEL TEL TEL E SCBSCB RD P E E RD RD SCB G W W W W FI B E R SS SS SS SS SS SS SS SS SS SS SS SS X X X X X X X X X X X X X X X X X X X X X X X X X W W W W W W W W W W W W W W W W W W SS SS SS SS SS SS SS SS SS SS SS SS MA T H E W S S T R E E T AL L E Y 36" NYLOPLAST JUNCTION W/ GRATE 15" INV (N) = 4978.30 SUMP = 4975.0 RIM = 4981.57 6" ROOF INV = 4978.50 MCINTYRE HOUSE LOT 26, BLOCK 131 ORIGINAL TOWN GARAGE LOT 1 LOT 2 LOT 3 LOT 4 LOT 5 LOT 6 LOT 7 LOT 8 LOT 9 LOT 10 LOT 11 LOT 15 LOT 14 LOT 13 LOT 12 LOT 17-18, BLOCK 131 ORIGINAL TOWN EAST 1/2 OF LOTS 19-22, BLOCK 131 ORIGINAL TOWN LOT 7-16, BLOCK 131 ORIGINAL TOWN STORMTECH 160 LP (12X2) BOTTOM ROCK = 4977.90 BOTTOM CHAMBERS = 4978.40 TOP CHAMBERS = 4979.40 TOP ROCK = 4979.90 MIN FG = 4981.07 6" ROOF DRAIN FOR EAST BUILDINGSTRACT A UE,DE, PRIVATE AE 2'X3' CURB INLET ADS NYLOPLAST FL = 4981.20 12" INV= 4978.45 15" HP INV = 4977.50 9.0 LF 15" HP @ 4.4% 36" NYLOPLAST BASIN W/ WEIR 12" HP INV= 4978.00 15" HP INV=4977.55 4" HP INV = 4977.55 TOP OF WEIR = 4979.50 36" NYLOPLAST BASIN 12" HP INV=4978.40 15" HP INV = 4978.40 9.5 LF 15" HP @ 0.5% 12" INV = 4978.50 6" PVC INV = 4978.30 4" PERF INV = 4977.70 8" PVC INV = 4978.40 8" PVC INV = 4978.40 8"X12" INV = 4979.50 4" PERF INV = 4978.0 6" ROOF INV = 4979.50 4" PERF PVC @ 0.3% (2) 17 LF 8" HP @ 0.5% 9.0 LF 12" HP @ 0.6% 12" ROOF DRAIN FOR WEST BUILDINGS 18.0 LF 15" HP @ 0.6% 8" HP INV=4977.29 8" HP INV=4977.20 24" AREA INLET W/ DOME GRATE 12" INV = 4978.60 GRATE= 4981.00 12" AREA INLET W/ DOME GRATE AND 8" LEADER INV = 4979.60 GRATE=4981.48 12" AREA INLET W/ DOME GRATE AND 8" LEADER INV = 4979.50 GRATE=4981.32 12" AREA INLET W/ DOME GRATE AND 8" LEADER INV = 4979.30 GRATE=4981.34 12" AREA INLET W/ DOME GRATE AND 8" LEADER INV = 4978.90 GRATE=4981.34 18.0 LF 12" HP @ 0.5% 40 6 5 S A I N T C L O U D D R I V E , S U I T E 2 0 1 LO V E L A N D , C O 8 0 5 3 8 PH O N E : 9 7 0 - 8 3 4 - 6 3 6 4 ww w . w i l s o n c o . c o m 811 UTILITY PLAN STORM 5 MPO AGW MPO 22-100-645-00 FEBRUARY 28, 2024 DRAWN BY: CHECKED BY: DATE: DE S C R I P T I O N DA T E PR O P E R T Y O W N E R SE A L PR O J E C T N A M E PROJECT NO: DESIGNED BY: SHEET NO: SHEET TITLE RE V . BY EA S T O A K T O W N H O M E S SU B D I V I S I O N PRE L I M I N A R Y S U B M I T T A L NOT F O R CON S T R U C T I O N NOTES: 1. ALL STORM, SANITARY, AND WATER AS WELL AS POWER AND OTHER "DRY" UTILITY INSTALLATIONS, SHALL CONFORM TO THE CITY OF FORT COLLINS STANDARDS AND SPECIFICATIONS CURRENT AT THE DATE OF APPROVAL OF THE PLANS BY THE LOCAL ENGINEER. 2. STORM SEWER PIPE SHALL BE RCP OR ADS HP WITH WATER TIGHT JOINTS AS SPECIFIED ON THE PLAN OR OTHERWISE NOTED. ALL STORM SEWER SHALL BE INSPECTED BY THE CITY OF FORT COLLINS (COFC). 3. LENGTH OF PIPE IS MEASURED FROM CENTER OF STRUCTURE TO CENTER OF STRUCTURE. 4. WATER MAINS AND FIRE LINES SHALL BE PVC(C900) AS SPECIFIED BY THE COFC. THE MINIMUM COVER OVER WATER LINES IS 4.5 FEET AND THE MAXIMUM COVER IS 5.5 FEET UNLESS OTHERWISE APPROVED BY THE COFC. 5. ALL WATER SERVICES SHALL BE INSTALLED AT A MINIMUM OF 5 FEET BELOW FINISHED FLOOR ELEVATION AND SHALL BE TYPE K COPPER AS SPECIFIED BY COFC. 6. ALL SANITARY SEWER PIPE SHALL BE PVC (SDR35) UNLESS OTHERWISE NOTED ON THE PLAN. SEWER PIPE SHALL BE AS SPECIFIED BY THE CITY OF FORT COLLINS STANDARD PLANS AND SPECIFICATIONS. 7. SEE ARCHITECTURAL DRAWINGS FOR WALL LOCATION DETAILS OF GAS METERS, ELECTRIC METERS, AND TELEPHONE TERMINALS. 8. LIMITS OF STREET CUT SHOWN ARE APPROXIMATE. FINAL LIMITS ARE TO BE DETERMINED IN THE FIELD BY CITY ENGINEER INSPECTOR. ALL REPAIRS TO BE IN ACCORDANCE WITH THE CITY STREET REPAIR STANDARDS. 9. ANY DAMAGED CURB, GUTTER AND SIDEWALK EXISTING PRIOR TO CONSTRUCTION, AS WELL AS STREETS, SIDEWALKS, CURBS AND GUTTERS DESTROYED, DAMAGED OR REMOVED DUE TO CONSTRUCTION OF THIS PROJECT, SHALL BE REPLACED OR RESTORED TO CITY OF FORT COLLINS STANDARDS AT THE IMPROVEMENTS AND/OR PRIOR TO THE ACCEPTANCE OF COMPLETED IMPROVEMENTS AND/OR PRIOR TO THE ISSUANCE OF THE FIRST CERTIFICATE OF OCCUPANCY. CC C D E V E L O P M E N T 22 1 E O A K S T . U N I T A FO R T C O L L I N S , C O 8 0 5 2 4 D APPENDIX D IMPERVIOUS AREA EXHIBIT AND LID CALCULATIONS RD RD SCB W AC SCBRD RD SCBSCB RD RD RD SCB ST W W W W X X X X X X X X X X X X E OAK STREET MA T T H E W S S T R E E T RD RD SCB W AC SCBRD RD SCBSCB RD RD RD SCB ST W W W W E OAK STREET MA T T H E W S S T R E E T 40 6 5 S A I N T C L O U D D R I V E , S U I T E 2 0 1 LO V E L A N D , C O 8 0 5 3 8 PH O N E : 9 7 0 - 8 3 4 - 6 3 6 4 ww w . w i l s o n c o . c o m SURFACE AREA (SF)% IMPERVIOUS IMPERVIOUS AREA (SF) ROOF 12532 90 11279 CONCRETE/ASPHALT 6103 100 6103 GRAVEL 0 40 0 LANDSCAPE 2297 2 46 TOTAL 20932 17428 SURFACE AREA (SF)% IMPERVIOUS IMPERVIOUS AREA (SF) ROOF 9905 90 8915 CONCRETE/ASPHALT 5884 100 5884 GRAVEL 0 40 0 LANDSCAPE 5143 2 103 TOTAL 20932 14902 IMPERVIOUS AREA EXHIBIT 1 MPO AGW MPO 22-100-356-00 DRAWN BY: CHECKED BY: DATE: DE S C R I P T I O N DA T E PR O P E R T Y O W N E R SE A L PR O J E C T N A M E PROJECT NO: DESIGNED BY: SHEET NO: SHEET TITLE RE V . BY PRE L I M I N A R Y S U B M I T T A L NOT F O R CON S T R U C T I O N EXISTING PROPOSED DECEMBER 20, 2023 EA S T O A K T O W N H O M E S SU B D I V I S I O N TR I B E D E V E L O P M E N T 24 4 N C O L L E G E A V E SU I T E 1 3 0 FO R T C O L L I N S , C O 8 0 5 2 4 EB RD RD SCB W AC SCBRD TEL TEL TEL E SCBSCB RD P E E RD RD SCB G W W W W FI B E R SS X X X X X X X X X X X X X X X X X X X X X X X X X MA T H E W S S T R E E T E OAK STREET AL L E Y MCINTYRE HOUSE LOT 26, BLOCK 131 ORIGINAL TOWN GARAGE LOT 1 LOT 2 LOT 3 LOT 4 LOT 5 LOT 6 LOT 7 LOT 8 LOT 9 LOT 10 LOT 11 LOT 15 LOT 14 LOT 13 LOT 12 LOT 17-18, BLOCK 131 ORIGINAL TOWN EAST 1/2 OF LOTS 19-22, BLOCK 131 ORIGINAL TOWN LOT 7-16, BLOCK 131 ORIGINAL TOWN TRACT A UE,DE, PRIVATE AE 4981.5 49 8 1 . 5 49 7 7 . 5 497 8 4978. 5 49 7 9 4979.5 4979.5 49 8 0 49 8 0 . 5 STORMTECH 160 LP (12X2) PERMANENT BMP EXHIBIT 2 MPO ES MPO 22-100-645-00 FEBRUARY 21, 2024 40 6 5 S A I N T C L O U D D R I V E , S U I T E 2 0 1 LO V E L A N D , C O 8 0 5 3 8 PH O N E : 9 7 0 - 8 3 4 - 6 3 6 4 ww w . w i l s o n c o . c o m DRAWN BY: CHECKED BY: DATE: DE S C R I P T I O N DA T E PR O P E R T Y O W N E R SE A L PR O J E C T N A M E PROJECT NO: DESIGNED BY: SHEET NO: SHEET TITLE RE V . BY EA S T O A K T O W N H O M E S SU B D I V I S I O N PRE L I M I N A R Y S U B M I T T A L NOT F O R CON S T R U C T I O N CC C D E V E L O P M E N T 22 1 E O A K S T . U N I T A FO R T C O L L I N S , C O 8 0 5 2 4 811 EXISTING MAJOR CONTOUR LEGEND EXISTING MINOR CONTOUR PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR PERMANENT STORMWATER QUALITY BMP (ADS STORMTECH SYSTEM) STORMWATER QUALITY BMP AREA TREATED BY PERMANENT Design Procedure Form: Extended Detention Basin (EDB) - Sedimentation Facility Project Name: East Oak Townhomes Project Number: 22-100-645-00 Company: Wilson & Co Designer: MPO Date: 1/30/2024 1. Basin Storage Volume A) Tributary Area's Imperviousness Ratio (i=Ia/100) Ia = 83 % i = 0.83 B) Contributing Watershed Area (Area) A = 0.48 acres C) Water Quality Capture Volume (WQCV) WQCV = 0.28 watershed inches 12-hour Drain Time (WQCV = 0.8 * (0.91 * i3 - 1.19 * i2 + 0.78i) ) D) Design Volume: Vol = WQCV/12 * Area * 1.2 Vol. = 0.013 ac-ft 585 cf DETENTION VOLUME CALCULATIONS Rational Volumetric (FAA) Method ISOLATOR ROW LOCATION: East Oak Townhomes PROJECT NO: 22-100-635-00 COMPUTATIONS BY: MPO DATE: 1/30/2024 Equations:Area trib. to pond =0.48 acre Developed flow = QD = CIA C (2) =0.87 Vol. In = Vi = T C I A = T QD Developed C A = 0.42 acre Vol. Out = Vo =K QPO T Release rate, QPO =0.1980 cfs storage = S = Vi - Vo K =1 (from fig 2.1) Rainfall intensity from City of Fort Collins IDF Curve (half of 2-year) Storm Rainfall QD Vol. In Vol. Out Storage Storage Duration, T Intensity, I (cfs)Vi Vo S S (min) (in/hr) (ft3) (ft 3) (ft 3) (ac-ft) 5 1.43 0.6 179 59 120 0.00 10 1.11 0.5 278 119 159 0.00 20 0.81 0.3 406 238 168 0.00 30 0.65 0.3 489 356 132 0.00 40 0.54 0.2 541 475 66 0.00 50 0.46 0.2 576 594 -18 0.00 60 0.41 0.2 616 713 -96 0.00 70 0.0 0 832 -832 -0.02 80 0.0 0 950 -950 -0.02 90 0.0 0 1069 -1069 -0.02 100 0.0 0 1188 -1188 -0.03 110 0.0 0 1307 -1307 -0.03 120 0.0 0 1426 -1426 -0.03 Provided Volume: 168 ft 3 0.004 acre-ft 231116 FAA isolator row.xls,FAA-100yr LOCATION: East Oak Townhomes PROJECT NO: 22-100-635-00 COMPUTATIONS BY: MPO DATE: 1/30/2024 A***B C D*E G H I J K WQCV (12 Hr.) for info only WQ Flow (1/2 Q2) Chamber Type Single Chamber Release Rate Through Fabric* Volume in one Chamber Chambers Provided Actual Release Rate Thru Fabric Required Storage Volume by FAA Method with Qin=B and Q out=H Min Number of Chambers for FAA Release Volume in Isolator Rows cf cfs cfs cf (G*D) cfs CF (I/E) (G*E) 585 0.6 SC-160LP 0.00824 6.85 24 0.198 168 25 164.4 * -SC160LP Single Chamber = 10.6 SF FABRIC (Area in ACAD detail) Fabric Release @ 0.35 gal/min/SF = 3.7 gal/min/chamber 3.7 gal/min = 0.008241 cfs/chamber Isolator Row Volume Check *** - Water Quality Volume shown for information only. The design approach is that all rows are "isolator rows" and the volume within the chambers is adequate to allow the water quality flow to pass through the fabric. All other flow will bubble up on the north end of the chambers and leave the site over land. New or Modified Impervious Area 17,428 sf Required Minimum Impervious Area to be Treated 13,071 sf Treatment - Underground WQ System (ADS) 16,503 sf Actual % of Impervious Area On-Site Treated by LID 95 % 75% On-Site Treatment by LID Requirement LID Table E APPENDIX E SOILS AND FLOODPLAIN INFORMATION Hydrologic Soil Group—Larimer County Area, Colorado (220 East Oak Townhomes Subdivision) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/29/2023 Page 1 of 4 44 9 2 7 5 0 44 9 2 7 6 0 44 9 2 7 7 0 44 9 2 7 8 0 44 9 2 7 9 0 44 9 2 8 0 0 44 9 2 8 1 0 44 9 2 8 2 0 44 9 2 8 3 0 44 9 2 7 5 0 44 9 2 7 6 0 44 9 2 7 7 0 44 9 2 7 8 0 44 9 2 7 9 0 44 9 2 8 0 0 44 9 2 8 1 0 44 9 2 8 2 0 44 9 2 8 3 0 493670 493680 493690 493700 493710 493720 493670 493680 493690 493700 493710 493720 40° 35' 10'' N 10 5 ° 4 ' 2 9 ' ' W 40° 35' 10'' N 10 5 ° 4 ' 2 6 ' ' W 40° 35' 7'' N 10 5 ° 4 ' 2 9 ' ' W 40° 35' 7'' N 10 5 ° 4 ' 2 6 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 20 40 80 120 Feet 0 5 10 20 30 Meters Map Scale: 1:413 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 18, Aug 24, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 2, 2021—Aug 25, 2021 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (220 East Oak Townhomes Subdivision) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/29/2023 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 94 Satanta loam, 0 to 1 percent slopes C 0.8 100.0% Totals for Area of Interest 0.8 100.0% 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 Component Percent Cutoff: None Specified Hydrologic Soil Group—Larimer County Area, Colorado 220 East Oak Townhomes Subdivision Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/29/2023 Page 3 of 4 Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado 220 East Oak Townhomes Subdivision Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/29/2023 Page 4 of 4 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 11/29/2023 at 9:58 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 105°4'45"W 40°35'22"N 105°4'8"W 40°34'54"N Basemap Imagery Source: USGS National Map 2023 SITE 4065 St. Cloud, Suite.201 Loveland, CO 80538 970-834-6364 phone