Loading...
HomeMy WebLinkAboutPOUDRE VALLEY PLAZA MIXED-USE - MJA210003 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT Poudre Valley Plaza Mixed Use Poudre Valley Plaza P.U.D. Lot 7 Fort Collins, CO Prepared for: Schuman Companies Inc. Mark Morrison 7385 Greendale Road, Unit 104 Windsor, CO 80528 701.590.0434 Prepared by: i2 Consultants, Inc. 16911 Potts Place Mead, CO 80542 Phone: 970.217.9148 Project Number: 1024-3 August 4, 2021 i2 Consultants, Inc. 16911 Potts Place, Mead, CO 970.217.9148 troy@i2-consultants.com August 4, 2021 Mr. Matt Simpson, PE, CFM Development Review Engineer City of Fort Collins Utilities 222 Laporte Avenue Fort Collins, CO 80524 RE: Final Drainage Report for Poudre Valley Plaza Mixed Use Lot 7, Poudre Valley Plaza P.U.D., Fort Collins, CO Dear Mr. Simpson: We are pleased to present this Final Drainage Report for Poudre Valley Plaza Mixed Use, Lot 7, Poudre Valley Plaza P.U.D. for your review and approval. This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual, September 2018. We look forward to your favorable review of this project and report. Please do not hesitate to contact our office if you have any questions. Sincerely, i2 Consultants, Inc. Troy W. Campbell, PE Senior Project Engineer ENGINEER’S CERTIFICATION I hereby certify that this report for the final drainage design of Poudre Valley Plaza Mixed Use, Lot 7, Poudre Valley Plaza P.U.D. was prepared by me (or under my direct supervision) in accordance with the provisions of the Fort Collins Storm Drainage Criteria Manual for the owners thereof. __________________________________________ Registered Professional Engineer State of Colorado No. 41159 (Seal) Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 2 i2 Consultants, Inc. Final Drainage Report Poudre Valley Plaza Mixed Use Lot 7, Poudre Valley Plaza P.U.D. Located within the Northwest Quarter of Section 35, Township 7 North, Range 69 West of the 6th P.M. City of Fort Collins, County of Larimer, State of Colorado TABLE OF CONTENTS Page I. GENERAL LOCATION AND DESCRIPTION 3 A. Site Location B. Description of Property II. DRAINAGE BASINS AND SUB-BASINS 4 A. Major Basin B. Sub-basin and Site Drainage III. DRAINAGE DESIGN CRITERIA 4 A. Regulations B. Development Criteria Reference and Constraints C. Hydrological Criteria D. Hydraulic Criteria IV. DRAINAGE FACILITY DESIGN 5 A. General Concept B. Specific Details V. SEDIMENT, EROSION CONTROL AND STORMWATER QUALITY 7 A. Temporary Sediment and Erosion Control B. Permanent Water Quality BMPs VI. CONCLUSIONS 9 A. Compliance with Standards B. Drainage Concept VII. REFERENCES 10 VIII. APPENDICIES 11 Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 3 i2 Consultants, Inc. I. GENERAL LOCATION AND DESCRIPTION A. Site Location: The proposed development is located in the northwest quarter of Section 35, Township 7 North, Range 69 West, of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. Furthermore, the project is north of Arbor Street Avenue and east of Shields Street. The legal description of the property is Lot 7, Poudre Valley Plaza P.U.D. The subject site is currently vacant. B. Description of Property: The subject development lot consists of roughly 0.25 acres. The area considered with this drainage report is roughly 0.43 acres. The proposed building will be within Lot 7 and the parking, landscaping, walks and accesses will be located on Tract A Poudre Valley Plaza P.U.D. The development of Lot 7 will consist of construction of a single building, walks and landscaping. A portion of the existing parking to the north of the building will be removed and replaced with this project. The site currently is vacant but has been overlot graded with the Poudre Valley Plaza P.U.D. improvements. The site is bound by Arbor Avenue to the south, existing commercial development to the north, east and west. The subject site generally slopes from south to north at varying slopes from 0% to 1%. A portion of the site drains to the east to the existing retention pond constructed as part of Poudre Valley Plaza P.U.D. The existing runoff from the subject property drains to the north in existing conveyances (curb, gutter, sheet flow) to the existing detention pond in the northeast corner of Poudre Valley Plaza P.U.D. According to the Natural Resources Conversation Service (NRCS) Web Soil Survey, the native soils in this area are Altvan-Santanta loams, 0 to 3 percent slopes (Map Unit Symbol #3), which is a Type B soil and Altvan-Satanta loams, 3 to 9 percent slopes (Map Unit Symbol #4), which is a Type B soil. Please refer to the NRCS soils information in the Appendix. Existing drainage facilities near or adjacent to the site include existing curb & gutter installed with Poudre Valley Plaza P.U.D. as well as an existing retention pond east of the site and existing detention pond north of the site. Furthermore, there is an existing storm drain system in Arbor Avenue. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 4 i2 Consultants, Inc. II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin: This site is located within the Mail Creek Basin as shown on the City of Fort Collins Master Drainage Plan. This basin historically generally flows from northwest to southeast. There no agricultural irrigation facilities within 100 feet of the property boundary for the proposed site. The site is shown on FEMA panel 08069C0986G, effective 05/02/2012. The subject site is located with Zone X of the FEMA panel. B. Sub-basin and Site Drainage: The proposed site generally directs runoff north to existing improvements. A portion of the site will drain east to the existing retention pond, due to existing grades and site constraints. The subject site is shown within Basins 1, 2 and 4 of the approved Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado, dated January 23, 1996, prepared by RBD, Inc. Engineering Consultants. There is a small portion of this site in the southeast corner that flows offsite to Arbor Avenue and was not accounted for in the above referenced report. There is no offsite runoff that reaches the subject property. The drainage patterns proposed with the subject improvements are generally consistent with the drainage patterns proposed with the above referenced report. III. DRAINAGE DESIGN CRITERIA A. Regulations: This report has been prepared in general accordance with the Fort Collins Stormwater Criteria Manual, September 2018 and the Urban Storm Drainage Criteria Manual (USDCM). B. Development Criteria Reference and Constraints: The subject site has been included in the following previous reports: Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 5 i2 Consultants, Inc. · Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado, dated January 23, 1996, prepared by RBD, Inc. Engineering Consultants. This report has been prepared in general accordance with the appropriate City and USDCM criteria and previous reports. C. Hydrological Criteria: Fort Collins Stormwater Criteria Manual, September 2018, as well as the USDCM. There are no deviations from the criteria in this report. The design storms for this project are the 2-year and the 100-year recurrence intervals. Runoff is calculated using the Rational Method since all basins are smaller than 5 acres. The Rational Method calculations are computed by the following: Q = ciA where: Q = Runoff in cubic feet per second c = Calculated runoff coefficient for design event i = Storm intensity in inches/hour A = Basin area in acres Hydrological calculations have been prepared in accordance with the Fort Collins Stormwater Criteria Manual, September 2018 as well as the USDCM. D. Hydraulic Criteria: Rational calculations were prepared using methodology outlined in the Fort Collins Stormwater Criteria Manual, September 2018. Hydraulic capacities were calculated using Hydraflow Express Extension for Autodesk Civil 3D, Version 2021. IV. DRAINAGE FACILITY DESIGN A. General Concept: The drainage patterns associated with the proposed improvements are generally consistent with the existing drainage patterns, flow and the drainage patterns proposed with the Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado. The proposed site generally directs runoff north to the existing detention pond in the northeast corner of Poudre Valley Plaza P.U.D. A portion of the site will drain east to the existing retention pond, due to existing grades and site constraints, as depicted within the Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 6 i2 Consultants, Inc. The runoff for the site was determined using the Rational Method, as detailed above. The proposed improvements have been divided into six (6) drainage basins. The basins have been created to direct runoff to existing and proposed facilities. B. Specific Details: Basin A Basin A (0.13 acres) is in the northwestern portion of the site and contains the northwestern portion of the proposed building, concrete sidewalks and landscaping. The basin generally drains from south to north. The runoff from the building will be captured in a proposed planter with rain garden for water quality purposes. The landscape area on the west side of the building will drain to the existing access. Basin B Basin B (0.11 acres) is in the northeastern portion of the site and contains the northeastern portion of the proposed building, concrete sidewalks and landscaping. The runoff from the building will be captured in a proposed planter with rain garden for water quality purposes. Basin C Basin C (0.03 acres) is along the northeastern portion of the site and contains proposed concrete sidewalks and landscaping. The basin drains to an existing slotted drain installed with the Poudre Valley Plaza P.U.D. and to the existing retention pond located east of Lot 7. Basin D Basin D (0.12 acres) is along the southwestern portion of the site and contains the southwestern portion of the proposed building and landscaping. The basin generally drains from north to south. The runoff from the building will be captured in a proposed rain garden for water quality. The basin will be released from the rain garden to the west to the existing access. Basin E Basin E (0.03 acres) is along the southeastern portion of the site and contains the southeastern portion of the proposed building and landscaping. The basin generally drains from north to south. The runoff from the building will be captured in a proposed rain garden for water quality. The basin will be released from the rain garden to the west to Basin D. Basin F Basin F (0.01) acres is in the southeastern portion of the site and will contain landscaping. This basin is in a low area of the subject site and will drain to the existing retention pond east of Lot 7. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 7 i2 Consultants, Inc. The subject site was considered in Basins 1 and 2 of the Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado. The imperviousness for the basins are provide below: Basin 1: 68.3% (0.81 “C” Value) Basin 2: 79.6% (0.87 “C” Value) The composite imperviousness calculated for this development is 56.6%, with a “C” value of 0.62. These values are below the assumed values in the overall development drainage report. No additional detention is required as a result of the proposed development of Lot 7. The drainage design for the subject development will reduce the amount of runoff into the retention pond. A portion of the subject site was designed to drain to the retention pond in the overall report. With the proposed layout and constraints of the proposed development, a small portion of runoff will drain north to the existing pond in the northeast corner of the site and not into the retention pond. The additional flow will be from roughly 700 s.f. of sidewalk to the north of the proposed building. The drainage design for the subject site will generally conform to the overall drainage design for Poudre Valley Plaza P.U.D. The flow patterns proposed with the subject development generally follow the patterns of the overall drainage report, with exceptions noted above. The proposed drainage from this site is not anticipated to have a negative impact on the existing facilities as the existing detention pond will provide for attenuation of the developed runoff. V. SEDIMENT, EROSION CONTROL AND STORMWATER QUALITY A. Temporary Sediment and Erosion Control: Several sediment and erosion control measures will be incorporated into the initial phase of construction. The initial sediment and erosion control measures to be installed shall include sediment control logs, as well as a vehicle tracking control mat at the construction entrance, inlet protection in Arbor Avenue and rock socks within the existing flowline of the access. An initial control measure will be the installation of construction fence around the development perimeter. Furthermore, additional measures for sediment and erosion control shall consist of providing an area designated for a concrete washout area. A stabilized staging area is proposed in the parking area to the north of the subject site. The initial measures for sediment and erosion control shall be maintained and updated as necessary during the interim and final stages of the project. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 8 i2 Consultants, Inc. Additionally, any area that has been disturbed by construction activities and left exposed for more than fourteen (14) days, shall receive drilled seeding and straw mulch at 2 tons/acre, until permanent landscaping or ground cover has been provided. Four Step Process to Minimize Adverse Impacts of Urbanization Employing runoff reduction practices: Water Quality will be utilized with this development. There will be landscaping around each side of the site and no new parking areas are proposed with this development. Implementing best management practices (BMPs): Water Quality will be provided in the form of rain gardens to capture runoff from the proposed building. An underdrain will be installed in the rain gardens along the southern portion of the site. Stabilizing Streams: The runoff from the subject site drains to paved surfaces and existing detention facilities. The runoff release from the overall development will be controlled by these existing facilities. Implementing site specific and other source control BMPs: A stabilized staging area will be provided to the north of the subject site on existing asphalt. Appropriate erosion and pollution control shall be installed around the staging area. B. Permanent Water Quality BMPs Rain gardens will be installed near each corner of the proposed building to provide permanent water quality. Water quality planters/rain gardens will be installed at two (2) areas along the northern portion of the proposed building. These rain gardens will treat runoff prior to being released to existing conveyances to the north of the site. The design volume is larger than the required volume for each planter. Rain gardens will also be installed along the southern portion of the building. These two (2) rain gardens will capture and treat runoff from the building, prior to being released to the existing access. The design volume for each rain garden along the southern side of the building is larger than the required volume. These measures were selected for permanent water quality due to the site constraints regarding the proposed layout and tight tolerance for elevations. Please refer to the Appendix for water quality/rain garden calculations. The existing detention pond in the northeast corner of the overall development does not contain a water quality component. The retention pond will provide water quality for runoff that reaches the pond. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 9 i2 Consultants, Inc. VI. CONCLUSIONS A. Compliance with Standards: The drainage design is in general compliance with the Fort Collins Stormwater Criteria Manual, September 2018 as well as the Urban Storm Drainage Criteria Manual (USDCM). Furthermore, the design is in general conformance with the approved Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado, dated January 23, 1996, prepared by RBD, Inc. Engineering Consultants. B. Drainage Concept: The runoff from this site will be conveyed by existing and proposed storm drainage improvements, including proposed curb, gutter, swales and rain gardens. The drainage design for this project should not negatively impact improvements downstream or the existing storm system. Permanent water quality for the site will be provided through rain gardens to slow runoff and provide a filter for runoff prior to leaving the subject site. Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 10 i2 Consultants, Inc. VII.REFERENCES 1. Fort Collins Stormwater Criteria Manual, dated September 2018. 2. Urban Drainage and Flood Control District, Drainage Criteria Manual Volumes 1, Revised August 2018, Volume 2, Revised September 2017 and the Volume 3, dated November 2010 and Updated October 2019. 3. Final Drainage and Erosion Control Study for Poudre Valley Plaza, Fort Collins, Colorado, dated January 23, 1996, prepared by RBD, Inc. Engineering Consultants. TRACT A P0UDRE VALLEY PLAZA P.U.D. ARBOR DRIVEPRIVATE ACCESSDRIVELOT 6 EXISTING BUILDING EXISTING RETENTION POND EXISTING TRASH ENCLOSURE PROPOSED BUILDING FF = 5082.40 LOT 7 WQEL=5085.6; OVERFLOW AT 5086.0; V = 143 CU.FT.WQEL=5085.6; OVERFLOW AT 5086.0; V = 123 CU.FT. WQ OVERFLOW AT 5082.50; V = 110 CU.FT. WQ OVERFLOW AT 5082.75; V = 47 CU.FT. PROPOSED BUILDING FF = 5083.40 5083 5083 50815082 JLB 6 FINAL DRAINAGE PLANC-6 NOTES Know what's below. before you dig.Call R LEGEND OF SYMBOLS SURVEY NOTES: SHEET OF SHEETSPOUDRE VALLEY PLAZA MIXED USEUTILITY PLANSCITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADONORTHWEST 1/4, SECTION 35, TOWNSHIP 7 NORTH, RANGE 69 WEST12 CITY OF FORT COLLINS, COLORADO UTILITY PLAN APPROVAL PRELIMINARY NOT FOR CONSTRUCTION 08/04/2021 BASIN RUNOFF SUMMARY WATER QUALITY SUMMARY Final Drainage Report Poudre Valley Plaza Mixed Use, Fort Collins, CO August 4, 2021 Page 11 i2 Consultants, Inc. VIII.APPENDICIES  Vicinity Map  FEMA & Existing Geotechnical Information  Hydrologic Calculations  Hydraulic Calculations  BMP Calculations  Excerpts from Previous Reports  Charts and Figures Vicinity Map © 2021 Microsoft Corporation © 2021 TomTom VICINITY MAP JLB POUDRE VALLEY PLAZA MIXED USE LOT 7 POUDRE VALLEY PLAZA P.U.D. FORT COLLINS, CO i2 Consultants, Inc. FEMA & Existing Geotechnical Information 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 8/3/2021 at 9:48 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°6'W 40°32'31"N 105°5'22"W 40°32'3"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 Soil Map—Larimer County Area, Colorado (PVP Mixed Use) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 1 of 344873204487330448734044873504487360448737044873804487320448733044873404487350448736044873704487380491930491940491950491960491970491980491990492000492010492020 491930 491940 491950 491960 491970 491980 491990 492000 492010 492020 40° 32' 13'' N 105° 5' 43'' W40° 32' 13'' N105° 5' 38'' W40° 32' 11'' N 105° 5' 43'' W40° 32' 11'' N 105° 5' 38'' WN 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: 1:482 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features 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 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 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. Soil Map—Larimer County Area, Colorado (PVP Mixed Use) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 3 Altvan-Satanta loams, 0 to 3 percent slopes 0.9 98.6% 4 Altvan-Satanta loams, 3 to 9 percent slopes 0.0 1.4% Totals for Area of Interest 0.9 100.0% Soil Map—Larimer County Area, Colorado PVP Mixed Use Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 3 of 3 Hydrologic Soil Group—Larimer County Area, Colorado (PVP Mixed Use) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 1 of 444873204487330448734044873504487360448737044873804487320448733044873404487350448736044873704487380491930491940491950491960491970491980491990492000492010492020 491930 491940 491950 491960 491970 491980 491990 492000 492010 492020 40° 32' 13'' N 105° 5' 43'' W40° 32' 13'' N105° 5' 38'' W40° 32' 11'' N 105° 5' 43'' W40° 32' 11'' N 105° 5' 38'' WN 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: 1:482 if printed on A landscape (11" x 8.5") 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 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 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 (PVP Mixed Use) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 3 Altvan-Satanta loams, 0 to 3 percent slopes B 0.9 98.6% 4 Altvan-Satanta loams, 3 to 9 percent slopes B 0.0 1.4% Totals for Area of Interest 0.9 100.0% 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 Hydrologic Soil Group—Larimer County Area, Colorado PVP Mixed Use Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 3 of 4 Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado PVP Mixed Use Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/3/2021 Page 4 of 4 i2 Consultants, Inc. Hydrologic Calculations Runoff Coeffecients Sub-Basins C-1 Project: PVP Mixed Use i2 Location: 1039 W. Horsetooth Consultants, Inc. Fort Collins, Colorado 16911 Potts Place, Mead, CO Project Number:1024-3 970.217.9148 Date: Aug-21 troy@i2-consultants.com All calculations presented are based upon the criteria set forth in the City of Fort Collins Storm Drainage Design Criteria September 2018 Basin A (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 1 % of site area Lawns, Sandy soil (flat <2%) 0.04 1642.0 0.15 2.00 30.1% Curb & gutter and walks 0.02 667.0 0.95 100.00 12.2% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.07 3151.0 0.95 90.00 57.7% Avg. 0.71 64.76 100.0% Total Area 0.13 0.71 64.76 Basin B (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 2 % of site area Lawns, Sandy soil (flat <2%) 0.03 1129.0 0.15 2.00 22.7% Curb & gutter and walks 0.01 353.0 0.95 100.00 7.1% Paved Parking & Drives 0.08 3497.0 0.95 100.00 70.2% Roofs 0.00 0.0 0.95 90.00 0.0% Avg. 0.77 77.78 100.0% Total Area 0.11 0.77 77.78 Basin C (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 3 % of site area Lawns, Sandy soil (flat <2%) 0.02 685.0 0.15 2.00 48.4% Curb & gutter and walks 0.02 731.0 0.95 100.00 51.6% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.00 0.0 0.95 90.00 0.0% Avg. 0.56 52.59 100.0% Total Area 0.03 0.56 52.59 Basin D (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 3 % of site area Lawns, Sandy soil (flat <2%) 0.07 3172.0 0.15 2.00 61.5% Curb & gutter and walks 0.00 0.0 0.95 100.00 0.0% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.05 1986.0 0.95 90.00 38.5% Avg. 0.46 35.88 100.0% Total Area 0.12 0.46 35.88 PVPImperv.xlsx\Sub-Basins 8/4/2021 Runoff Coeffecients Sub-Basins C-2 Basin E (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 3 % of site area Lawns, Sandy soil (flat <2%) 0.02 729.0 0.15 2.00 50.7% Curb & gutter and walks 0.00 120.0 0.95 100.00 8.4% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.01 588.0 0.95 90.00 40.9% Avg. 0.54 46.19 100.0% Total Area 0.03 0.54 46.19 Basin F (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 3 % of site area Lawns, Sandy soil (flat <2%) 0.01 427.0 0.15 2.00 100.0% Curb & gutter and walks 0.00 0.0 0.95 100.00 0.0% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.00 0.0 0.95 90.00 0.0% Avg. 0.15 2.00 100.0% Total Area 0.01 0.15 2.00 Overall Site (ac) (sq.ft) (%) Design Point publish Area Area C I Comments 1 % of site area Lawns, Sandy soil (flat <2%) 0.18 7784.0 0.15 2.00 41.2% Curb & gutter and walks 0.04 1871.0 0.95 100.00 9.9% Paved Parking & Drives 0.08 3497.0 0.95 100.00 18.5% Roofs 0.13 5725.0 0.95 90.00 30.3% Avg. 0.62 56.56 100.0% Total Area 0.43 18877.00 0.62 56.56 PVPImperv.xlsx\Sub-Basins 8/4/2021 C-3PROJECT:PVP Mixed UseCALCULATED BY:i2 Consultants, Inc.DATE:8/4/2021Cf = 1.00FINAL REMARKStcBASIN DP AREA CC*CfLength SlopetiLength Slope VtttcTotal LtcID Ac Ft % min Ft % fps min min ft min min(0) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)1A 1 0.13 0.71 0.71 85 2.0 5.3 30 1.00 1.5 0.3 5.7 115 10.65.7Use Tc = 5.7 mins2B 2 0.11 0.77 0.77 85 2.0 4.5 70 1.0 1.5 0.8 5.3 155 10.95.3Use Tc = 5.3 mins3C 3 0.03 0.56 0.56 5 0.5 2.8 20 1.0 2.8 0.1 2.9 25 10.15.0Use Tc = 5.0 mins4D 4 0.12 0.46 0.46 20 2.0 4.3 115 0.5 0.7 2.7 7.0 135 10.87.0Use Tc = 7.0 mins5E 5 0.03 0.54 0.54 20 2.0 3.7 30 0.5 0.7 0.7 4.4 50 10.35.0Use Tc = 5.0 mins6F 6 0.01 0.15 0.15 15 2.0 5.5 20 1.0 1.5 0.2 5.7 35 10.25.7Use Tc = 5.7 minsEquations:UrbanizedTovtt =Ltc =(L/180)+1060VV=CvSw0.5(1)(2) or Fig. 3-3 (3)TRAVEL TIME(tt)tc CHECKS ^1/3Rural/Non-urban(URBANIZED)RURAL OR NON URBANIZEDTIME OF CONCENTRATION - 2-YEAR1.87(1.1-CCf)*D^1/2DATASUB-BASIN INITIAL/OVERLANDTIME (Tov) C-4PROJECT:PVP Mixed UseCALCULATED BY:i2 Consultants, Inc.DATE:8/4/2021Cf = 1.25FINAL REMARKStcBASIN DP AREA CC*CfLength SlopetiLength Slope VtttcTotal LtcID Ac Ft % min Ft % fps min min ft min min(0) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)1A 1 0.13 0.71 0.89 85 2.0 2.9 30 1.00 1.5 0.3 3.3 115 10.65.0Use Tc = 5.0 mins2B 2 0.11 0.77 0.96 85 2.0 1.9 70 1.0 1.5 0.8 2.7 155 10.95.0Use Tc = 5.0 mins3C 3 0.03 0.56 0.70 5 0.5 2.1 20 1.0 2.8 0.1 2.2 25 10.15.0Use Tc = 5.0 mins4D 4 0.12 0.46 0.57 20 2.0 3.5 115 0.5 0.7 2.7 6.2 135 10.86.2Use Tc = 6.2 mins5E 5 0.03 0.54 0.68 20 2.0 2.8 30 0.5 0.7 0.7 3.5 50 10.35.0Use Tc = 5.0 mins6F 6 0.01 0.15 0.19 15 2.0 5.2 20 1.0 1.5 0.2 5.5 35 10.25.5Use Tc = 5.5 minsEquations:UrbanizedTovtt =Ltc =(L/180)+1060VV=CvSw0.5(1)(2) or Fig. 3-3 (3)S ^1/3Rural/Non-urban(URBANIZED)RURAL OR NON URBANIZEDTIME OF CONCENTRATION - 100-YEAR1.87(1.1-CCf)*D^1/2DATASUB-BASIN INITIAL/OVERLANDTIME (Tov)TRAVEL TIME(tt)tc CHECK Rational Method Direct Runoff - 2-YR C-5 Project: PVP Mixed Use i2 Consultants, Inc. Location: 1039 W. Horsetooth 16911 Potts Place, Mead, CO Fort Collins, Colorado 970.217.9148 Project Number:1024-3 troy@i2-consultants.com Date: 8/4/2021 Rational Method:Q = CfCIA Q: Q: Runoff in cfs (peak) C: C: Runoff Coefficient Cf: Cf: Frequency Adjustment Factor I: I: Rainfall Intensity (in/hr) for design event A: A: Basin Area (acres) 2-YEAR Design Point Basin ID Area C CfC tc I Q2 1 A 0.13 0.71 0.71 5.7 9.50 0.84 6.7 cfs/acre 2 B 0.11 0.77 0.77 5.3 9.76 0.86 7.5 cfs/acre 3 C 0.03 0.56 0.56 5.0 9.95 0.18 5.6 cfs/acre 4 D 0.12 0.46 0.46 7.0 8.80 0.13 1.1 cfs/acre 5 E 0.03 0.54 0.54 5.0 9.95 0.18 5.3 cfs/acre 6 F 0.01 0.15 0.15 5.7 9.50 0.05 4.7 cfs/acre C:\Users\troy\Dropbox\I2\Projects\1024-3 PVP\Documents\Drainage\PVP_rational.xlsx 8/4/2021 Rational Method Direct Runoff - 100-YR C-6 Project: PVP Mixed Use i2 Consultants, Inc. Location: 1039 W. Horsetooth 16911 Potts Place, Mead, CO Fort Collins, Colorado 970.217.9148 Project Number:1024-3 troy@i2-consultants.com Date: 8/4/2021 Rational Method:Q = CfCIA Q: Q: Runoff in cfs (peak) C: C: Runoff Coefficient Cf: Cf: Frequency Adjustment Factor I: I: Rainfall Intensity (in/hr) for design event A: A: Basin Area (acres) 100-YEAR Design Point Basin ID Area C CfC tc I Q100 1 A 0.13 0.71 0.89 5.0 9.95 1.11 8.8 cfs/acre 2 B 0.11 0.77 0.96 5.0 9.95 1.09 9.6 cfs/acre 3 C 0.03 0.56 0.70 5.0 9.95 0.23 7.0 cfs/acre 4 D 0.12 0.46 0.57 6.2 9.21 0.17 1.4 cfs/acre 5 E 0.03 0.54 0.68 5.0 9.95 0.22 6.7 cfs/acre 6 F 0.01 0.15 0.19 5.5 9.63 0.06 6.0 cfs/acre C:\Users\troy\Dropbox\I2\Projects\1024-3 PVP\Documents\Drainage\PVP_rational.xlsx 8/4/2021 i2 Consultants, Inc. Hydraulic Calculations Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, Aug 3 2021 Typical Sidewalk Chase (Max. flow from Basin is 1.11 cfs) Rectangular Bottom Width (ft) = 2.00 Total Depth (ft) = 0.50 Invert Elev (ft) = 5082.11 Slope (%) = 1.00 N-Value = 0.025 Calculations Compute by: Q vs Depth No. Increments = 10 Highlighted Depth (ft) = 0.30 Q (cfs) = 1.341 Area (sqft) = 0.60 Velocity (ft/s) = 2.24 Wetted Perim (ft) = 2.60 Crit Depth, Yc (ft) = 0.25 Top Width (ft) = 2.00 EGL (ft) = 0.38 0 .5 1 1.5 2 2.5 3 Elev (ft)Depth (ft)Section 5081.75 -0.36 5082.00 -0.11 5082.25 0.14 5082.50 0.39 5082.75 0.64 5083.00 0.89 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, Aug 3 2021 Basin D Overflow from Rain Garden Trapezoidal Bottom Width (ft) = 3.00 Side Slopes (z:1) = 8.00, 8.00 Total Depth (ft) = 0.25 Invert Elev (ft) = 5082.50 Slope (%) = 0.50 N-Value = 0.035 Calculations Compute by: Q vs Depth No. Increments = 10 Highlighted Depth (ft) = 0.25 Q (cfs) = 1.186 Area (sqft) = 1.25 Velocity (ft/s) = 0.95 Wetted Perim (ft) = 7.03 Crit Depth, Yc (ft) = 0.15 Top Width (ft) = 7.00 EGL (ft) = 0.26 0 1 2 3 4 5 6 7 8 9 Elev (ft)Depth (ft)Section 5082.00 -0.50 5082.25 -0.25 5082.50 0.00 5082.75 0.25 5083.00 0.50 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Wednesday, Aug 4 2021 Swale X-Section from Rain Gardens Triangular Side Slopes (z:1) = 6.00, 6.00 Total Depth (ft) = 0.50 Invert Elev (ft) = 5082.00 Slope (%) = 0.50 N-Value = 0.025 Calculations Compute by: Q vs Depth No. Increments = 10 Highlighted Depth (ft) = 0.40 Q (cfs) = 1.367 Area (sqft) = 0.96 Velocity (ft/s) = 1.42 Wetted Perim (ft) = 4.87 Crit Depth, Yc (ft) = 0.32 Top Width (ft) = 4.80 EGL (ft) = 0.43 0 1 2 3 4 5 6 7 8 Elev (ft)Depth (ft)Section 5081.75 -0.25 5082.00 0.00 5082.25 0.25 5082.50 0.50 5082.75 0.75 5083.00 1.00 Reach (ft) i2 Consultants, Inc. BMP Calculations Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =90.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.900 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.32 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 3,151 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =84 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =8 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =57 sq ft D) Actual Flat Surface Area AActual =215 sq ft E) Area at Design Depth (Top Surface Area)ATop =215 sq ft F) Rain Garden Total Volume VT=143 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =0.3 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =84 cu ft iii) Orifice Diameter, 3/8" Minimum DO =5/16 in LESS THAN MINIMUM. USE DIAMETER OF 3/8" Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - NW WQ Planter 1039 Horsetooth, Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO PVP_BMPNW_WQ.xlsm, RG 8/4/2021, 4:42 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation NO SPRINKLER HEADS ON FLAT SURFACE A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - NW WQ Planter 1039 Horsetooth, Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO PVP_BMPNW_WQ.xlsm, RG 8/4/2021, 4:42 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =90.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.900 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.32 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 3,497 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =94 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =8 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =63 sq ft D) Actual Flat Surface Area AActual =185 sq ft E) Area at Design Depth (Top Surface Area)ATop =185 sq ft F) Rain Garden Total Volume VT=123 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =0.3 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =94 cu ft iii) Orifice Diameter, 3/8" Minimum DO =5/16 in LESS THAN MINIMUM. USE DIAMETER OF 3/8" Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - NE WQ Planter 1039 Horsetooth, Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO PVP_BMPNE_WQ.xlsm, RG 8/4/2021, 4:43 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - NE WQ Planter 1039 Horsetooth, Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO PVP_BMPNE_WQ.xlsm, RG 8/4/2021, 4:43 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =90.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.900 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.32 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 1,986 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =53 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =4 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =36 sq ft D) Actual Flat Surface Area AActual =240 sq ft E) Area at Design Depth (Top Surface Area)ATop =420 sq ft F) Rain Garden Total Volume VT=110 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =0.3 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =53 cu ft iii) Orifice Diameter, 3/8" Minimum DO =1/4 in LESS THAN MINIMUM. USE DIAMETER OF 3/8" Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - SW WQ Planter 1039 Horsetooth, Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO PVP_BMPSW_WQ.xlsm, RG 8/4/2021, 4:43 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - SW WQ Planter 1039 Horsetooth, Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO PVP_BMPSW_WQ.xlsm, RG 8/4/2021, 4:43 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =90.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.900 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.32 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 588 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =16 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =4 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =11 sq ft D) Actual Flat Surface Area AActual =110 sq ft E) Area at Design Depth (Top Surface Area)ATop =170 sq ft F) Rain Garden Total Volume VT=47 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =0.3 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =16 cu ft iii) Orifice Diameter, 3/8" Minimum DO =1/8 in LESS THAN MINIMUM. USE DIAMETER OF 3/8" Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - SE WQ Planter 1039 Horsetooth, Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO PVP_BMPSE_WQ.xlsm, RG 8/4/2021, 4:44 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) twc i2 Consultants, Inc. August 4, 2021 PVP Mixed Use - SE WQ Planter 1039 Horsetooth, Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO PVP_BMPSE_WQ.xlsm, RG 8/4/2021, 4:44 AM i2 Consultants, Inc. Excerpts from Previous Reports i2 Consultants, Inc. Charts and Figures FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.2 Runoff Coefficients Page 5 Table 3.2-2. Surface Type - Runoff Coefficients Surface Type Runoff Coefficients Hardscape or Hard Surface Asphalt, Concrete 0.95 Rooftop 0.95 Recycled Asphalt 0.80 Gravel 0.50 Pavers 0.50 Landscape or Pervious Surface Lawns, Sandy Soil, Flat Slope < 2% 0.10 Lawns, Sandy Soil, Avg Slope 2-7% 0.15 Lawns, Sandy Soil, Steep Slope >7% 0.20 Lawns, Clayey Soil, Flat Slope < 2% 0.20 Lawns, Clayey Soil, Avg Slope 2-7% 0.25 Lawns, Clayey Soil, Steep Slope >7% 0.35 3.2.1 Composite Runoff Coefficients Drainage sub-basins are frequently composed of land that has multiple surface types or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: ( ) t n i ii A xAC C ∑ ==1 Equation 5-2 Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (Ai), dimensionless Ai = Area of Surface with Runoff Coefficient of Ci, acres or square feet n = Number of different surfaces to be considered At = Total Area over which C is applicable, acres or square feet 3.2.2 Runoff Coefficient Frequency Adjustment Factor The runoff coefficients provided in Table 3.2-1 and Table 3.2-2 are appropriate for use with the 2-year storm event. For any analysis of storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapotranspiration and other losses that have a proportionally smaller effect on high-intensity storm runoff. This adjustment is FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.3 Time of Concentration Page 6 applied to the composite runoff coefficient. These frequency adjustment factors, Cf, are found in Table 3.2-3. Table 3.2-3. Frequency Adjustment Factors Storm Return Period (years) Frequency Adjustment Factor (Cf) 2, 5, 10 1.00 25 1.10 50 1.20 100 1.25 3.3 Time of Concentration 3.3.1 Overall Equation The next step to approximate runoff using the Rational Method is to estimate the Time of Concentration, Tc, or the time for water to flow from the most remote part of the drainage sub-basin to the design point under consideration. The Time of Concentration is represented by the following equation: 𝐓𝐓𝐜𝐜=𝐓𝐓𝐢𝐢+𝐓𝐓𝐭𝐭 Equation 5-3 Where: Tc = Total Time of Concentration, minutes Ti = Initial or Overland Flow Time of Concentration, minutes Tt = Channelized Flow in Swale, Gutter or Pipe, minutes 3.3.2 Overland Flow Time Overland flow, Ti, can be determined by the following equation: 𝐓𝐓𝐢𝐢=𝟏𝟏.𝟖𝟖𝟖𝟖(𝟏𝟏.𝟏𝟏−𝐂𝐂𝐂𝐂𝐂𝐂𝐟𝐟)√𝐋𝐋√𝐒𝐒𝟑𝟑 Equation 3.3-2 Where: C = Runoff Coefficient, dimensionless Cf = Frequency Adjustment Factor, dimensionless L = Length of Overland Flow, feet S = Slope, percent CXCF PRODUCT OF CXCF CANNOT EXCEED THE VALUE OF 1 OVERLAND FLOW LENGTH L=200’ MAX IN DEVELOPED AREAS L=500’ MAX IN UNDEVELOPED AREAS FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 4.0 SWMM 4.1 Input Parameters Page 11 Table 4.1-2. Land Use - Percent Impervious Land Use Percent Impervious (%) Residential Urban Estate 30 Low Density 50 Medium Density 70 High Density 90 Commercial Commercial 80 Industrial 90 Undeveloped Open Lands, Transition 20 Greenbelts, Agriculture 2 Offsite Flow Analysis (when Land Use not defined) 45 Reference: For further guidance regarding zoning classifications, refer to the Land Use Code, Article 4. For Final Plan (FP) submittals, impervious values must be based on the proposed land surface types. Refer to Table 4.1-3 for recommended percent impervious values. Table 4.1-3. Surface Type – Percent Impervious Surface Type Percent Impervious (%) Hardscape or Hard Surface Asphalt, Concrete 100 Rooftop 90 Recycled Asphalt 80 Gravel 40 Pavers 40 Landscape or Pervious Surface Playgrounds 25 Lawns, Sandy soil 2 Lawns, Clayey soil 2 TRACT A P0UDRE VALLEY PLAZA P.U.D. ARBOR DRIVEPRIVATE ACCESSDRIVELOT 6 EXISTING BUILDING EXISTING RETENTION POND EXISTING TRASH ENCLOSURE PROPOSED BUILDING FF = 5082.40 LOT 7 WQEL=5085.6; OVERFLOW AT 5086.0; V = 143 CU.FT.WQEL=5085.6; OVERFLOW AT 5086.0; V = 123 CU.FT. WQ OVERFLOW AT 5082.50; V = 110 CU.FT. WQ OVERFLOW AT 5082.75; V = 47 CU.FT. PROPOSED BUILDING FF = 5083.40 5083 5083 50815082 JLB 6 FINAL DRAINAGE PLANC-6 NOTES Know what's below. before you dig.Call R LEGEND OF SYMBOLS SURVEY NOTES: SHEET OF SHEETSPOUDRE VALLEY PLAZA MIXED USEUTILITY PLANSCITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADONORTHWEST 1/4, SECTION 35, TOWNSHIP 7 NORTH, RANGE 69 WEST12 CITY OF FORT COLLINS, COLORADO UTILITY PLAN APPROVAL PRELIMINARY NOT FOR CONSTRUCTION 08/04/2021 BASIN RUNOFF SUMMARY WATER QUALITY SUMMARY