The URL can be used to link to this page

Home My WebLink AboutMEYER SUBDIVISION - FDP190006 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTKEEFE CIVIL, LLC 825 Union Street Golden, Colorado 80401 (970) 215-6808 April 23, 2019 Keefe Civil Project Number: 2018-025 Shane Boyle Development Review Engineer Stormwater Engineering & Development Review Division City of Fort Collins Utilities 700 Wood Street Fort Collins, Colorado 80522 RE: Meyer Subdivision, FDP190006 Drainage and Erosion Control Memo Dear Shane: The purpose of this letter is to address the drainage impacts to the existing 2.21 acre residential lot at 2200 Kechter Road due to the proposed site improvements (Appendix A). The site is located 0.1 mile east of South Timberline Road, on the north side of Kechter road, and is bound by urban estate residential properties to the west, north, and east. The existing site is a developed urban estate residential lot with two residential homes, a gravel driveway, two existing water wells, and several outbuildings. The vegetation is sparse and the soil consists of Fort Collins loam and Nunn clay loam per the NRCS Soil Survey of Larimer County (Appendix B). Per the flood insurance rate map (Appendix C), the lot is located within Zone X. Zone X is defined as an area of minimal flood hazard and does not have a base flood elevation associated with it. The local topography generally slopes from the south to north behind the existing right-of-way fence. The total existing impervious area is 14,577 square feet (sf) or 18%. The proposed grading and drainage design for the site (Appendix A) follows the existing drainage patterns and does not result in concentrated flow leaving the property. One of the single-family residences and an outbuilding will be relocated offsite. The total impervious area will increase slightly to 18,791 sf or 20%. Hardscape or Hard Surface Historic Area (sf) Developed Area (sf) Change in Impervious Area (sf) Asphalt, Concrete 100 843 Rooftop 4,917 6,717 Fire Lane 0 9,746 Gravel 9,560 1,485 Total Impervious Area 14,577 18,791 4,214 Meyer Subdivision, FDP190006 Keefe Civil Project No.: 2018-025 Page 2 of 2 April 23, 2019 The composite C values and basin flow calculations for the historic and developed site are included in the enclosed tables (Appendix D). Using the Fort Collins Stormwater Criteria Manual, the estimated site runoff increases will be negligible with the 2-year, 10-year, and 100-year flows. 2-year 10-year 100-year Historic runoff 0.79 cfs 1.36 cfs 3.63 cfs Developed runoff 0.93 cfs 1.59 cfs 4.28 cfs In my professional opinion, the additional runoff generated by this development will not cause adverse impacts to downstream private properties. Therefore, Keefe Civil respectfully requests no detention and water quality requirements be imposed on this development. Erosion Control Measures The structural practices for the site will consist mainly of silt fence, vehicle tracking control pad, and concrete washout area. The locations of these structural practices are shown in Appendix A. The corresponding construction control measures fact sheets are included in Appendix E. After construction has been completed at the site, all disturbed areas shall be seeded with dryland native seed mix per approved plans or landscaped. The anticipated disturbed area is estimated at 0.54 acre. The City of Fort Collins erosion and sediment control escrow calculations for the site are included in Appendix F. Thank you for the opportunity to submit this drainage and erosion control memo. Please do not hesitate to reach out to me if you have any questions or comments regarding the above items. (970) 215-6808 Best regards, Megan L. Keefe, PE / Manager Keefe Civil, LLC Enclosures Cc: Adam Meyer, Owner Kim Rose, Rose Custom Homes APPENDIX A FORT COLLINS, COLORADO SHEET MEYER SUBDIVISION UTILITY PLANS KEEFE CIVIL, LLC 825 UNION STREET GOLDEN, CO 80401 (970) 215-6808 MEG@KEEFECIVIL.COM City of Ft. Collins, Colorado UTILITY PLAN APPROVAL APPROVED: City Engineer Date CHECKED BY: Water & Wastewater Utility Date CHECKED BY: Stormwater Utility Date CHECKED BY: Parks & Recreation Date CHECKED BY: Traffic Engineer Date CHECKED BY: Natural Resources Date FORT COLLINS - LOVELAND WATER DISTRICT SOUTH FORT COLLINS SANITATION DISTRICT Mr. Chris Matkins, Manager Date Mr. Terry Ferrill, P.E., District Manager Date All changes, addendums, additions, deletions and modifications to these drawings must be approved, in writing, by the Fort Collins-Loveland EXISTING IMPERVIOUS AREA: Water District and the South Fort Collins Sanitation District. ROOFTOP 4,917 SF CONCRETE 300 SF GRAVEL DRIVEWAY 9,560 SF TOTAL 14,577 SF NEW IMPERVIOUS AREA: ROOFTOP 6,717 SF CONCRETE 843 SF FIRE LANE 9,746 SF GRAVEL DRIVEWAY 1,485 SF NEW TOTAL 18,791 SF CHANGE IN IMPERVIOUS AREA = + 4,214 SF GRADING NOTES: 1. TOP OF FOUNDATION MUST BE AT LEAST 6" ABOVE THE HIGHEST GRADE SURROUNDING ALL PROPOSED BUILDINGS. 2. THERE MUST BE A MINIMUM GRADE OF 5% AWAY FROM THE FOUNDATION WITHIN THE FIRST 5 TO 10 FEET ADJACENT TO ALL PROPOSED BUILDINGS. 3. ALL SLOPES MUST MEET THE MINIMUM REQUIREMENT OF 1% AND ARE NOT TO BE STEEPER THAN 33% (3:1). PROPOSED BUILDING TOF = 4948.60' KECHTER ROAD CENTERLINE FUTURE SAGE CREEK ROAD (51' ROW) 1 2.15 THORLAND SUBDIVISION DS DS APPENDIX B Soil Map—Larimer County Area, Colorado (Meyer Subdivision) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/18/2019 Page 1 of 3 4484270 4484290 4484310 4484330 4484350 4484370 4484390 4484410 4484430 4484270 4484290 4484310 4484330 4484350 4484370 4484390 4484410 4484430 496790 496810 496830 496850 496870 496890 496910 496790 496810 496830 496850 496870 496890 496910 40° 30' 38'' N 105° 2' 16'' W 40° 30' 38'' N 105° 2' 11'' W 40° 30' 32'' N 105° 2' 16'' W 40° 30' 32'' N 105° 2' 11'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:864 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 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 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 36 Fort Collins loam, 3 to 5 percent slopes 0.9 37.9% 73 Nunn clay loam, 0 to 1 percent slopes 1.5 59.1% 74 Nunn clay loam, 1 to 3 percent slopes 0.1 3.0% Totals for Area of Interest 2.5 100.0% Soil Map—Larimer County Area, Colorado Meyer Subdivision Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/18/2019 Page 3 of 3 APPENDIX C USGS The National Map: Orthoimagery. Data refreshed October, 2017. National Flood Hazard Layer FIRMette 0 250 500 1,000 1,500 2,000 Feet Ü 105°2'32.52"W 40°30'46.53"N 105°1'55.06"W 40°30'19.17"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT HAZARD SPECIAL AREAS FLOOD Without Zone A, V, Base A99 Flood Elevation (BFE) With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas depth areasdrainage of less less than than one one foot square or with mile Zone X Future ChanceAnnual Conditions Flood Hazard 1% Zone X Area Levee.to with See Reduced Notes. Flood Risk due Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone 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 digital map flood complies maps if with it is FEMA's not void standards as described for the below. use of The accuracy basemap standards shown complies with FEMA's basemap The authoritative flood hazard NFHL information web services is derived provided directly by FEMA. from This the map was reflectnot exported changes on or 2/amendments 19/2019 at 1:subsequent 56:49 AM to and this does date and time. becomeor The superseded NFHL and effective by new data information over time. may change This elementsmap map image do not is appear: void if basemap the one or imagery, more of flood the following zone labels, legend, FIRM panel scale number, bar, map and creation FIRM effective date, community date. Map identifiers,images for unmapped regulatoryfor purposes. and unmodernized areas cannot be used Legend OTHER FLOOD AREAS HAZARD OF OTHER AREAS STRGUECNTUERREASL FEATURES OTHER MAP PANELS 8 1:6,000 B 20.2 The point pin selected displayed by the on the user map and is does an approximate not represent an authoritative property location. APPENDIX D Composite C Values Meyer Subdivision Surface Type Runoff Coefficients1 Historic Area (sf) Minor (2-yr) Historic Composite C2 Major (100-yr) Historic Composite C2 Developed Area (sf) Minor (2-yr) Developed Composite C2 Major (100-yr) Developed Composite C2 Hardscape or Hard Surface Asphalt, Concrete 0.95 100 843 Rooftop 0.95 4,917 6,717 Fire Lane 0.80 0 9,746 Gravel 0.50 9,560 1,485 Total Impervious Area 14,577 18,791 Landscape or Pervious Surface Lawns, Clayey Soil, Avg Slope 2-7% 0.25 0 8,815 Undeveloped Greenbelts, Agriculture 0.20 78,890 65,861 Total Drainage Basin Area 93,467 0.27 0.34 93,467 0.31 0.39 Notes: 1. Runoff Coefficients per Fort Collins Stormwater Criteria Manual Table 3.2-2. 2. Frequency adjustment factor per Fort Collins Stormwater Criteria Manual Table 3.2-3. Meyer - drainage.xlsx Basin Flow Calculations Meyer Subdivision Length (ft) Slope (%) Minor to (min) Major to (min) Length (ft) Slope (%) Channel Type Velocity (fps) tt (min) Minor Tc (min) Major Tc (min) 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr 1 A 2.146 0.27 0.34 485 2 27.1 24.9 NA 27.1 24.9 1.37 2.34 5.00 0.79 1.36 3.63 1 A 2.146 0.31 0.39 485 2 25.9 23.3 NA 25.9 23.3 1.41 2.40 5.17 0.93 1.59 4.28 Notes: 3. Per Fort Collins Stormwater Criteria Manual Section 3.3.4. 2. Per Fort Collins Stormwater Criteria Manual Section 3.3.3. 1. Per Fort Collins Stormwater Criteria Manual Section 3.3.2. 4. Per IDF Table for Rational Method, Table 3.4-1 Fort Collins Stormwater 5. Per Fort Collins Stormwater Criteria Manual Equation 5-1. Initial/Overland Time1 Travel Time2 Historical Developed Final Tc 3 Intensity (in/hr) 4 Design Point Basin Area (acres) Minor Composite C Major Composite C Basin Flow (cfs) 5 Meyer - drainage.xlsx APPENDIX E Concrete Washout Area (CWA) MM-1 November 2010 Urban Drainage and Flood Control District CWA-3 Urban Storm Drainage Criteria Manual Volume 3 MM-1 Concrete Washout Area (CWA) CWA-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Silt Fence (SF) SC-1 November 2010 Urban Drainage and Flood Control District SF-3 Urban Storm Drainage Criteria Manual Volume 3 SC-1 Silt Fence (SF) SF-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Stockpile Management (SP) MM-2 November 2010 Urban Drainage and Flood Control District SP-3 Urban Storm Drainage Criteria Manual Volume 3 MM-2 Stockpile Management (SM) SP-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Vehicle Tracking Control (VTC) SM-4 November 2010 Urban Drainage and Flood Control District VTC-3 Urban Storm Drainage Criteria Manual Volume 3 SM-4 Vehicle Tracking Control (VTC) VTC-6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 APPENDIX F Project: Disturbed Acres: 0.54 EROSION CONTROL BMPs Estimated Quantity Units Unit Price Total Price 425 LF $2.00 $850.00 1 EA $500.00 $500.00 1 EA $500.00 $500.00 Sub-Total: $1,850.00 1.5 x Sub-Total: $2,775.00 Amount of security: $2,775.00 Total Acres x Price/acre: $390.08 $720.00 Sub-Total: $390.08 1.5 x Sub-Total: $585.12 Amount to Re-seed: $585.12 Minimum escrow amount: $1,500.00 Erosion Control Escrow: $2,775.00 Miniumum Escrow Amount Meyer Subdivision Unit Price of Seeding per acre: “The amount of the security must be based on one and one-half times the estimate of the cost to install the approved measures, or one and one-half times the cost to re-vegetate the disturbed land to dry land grasses based upon unit cost determined by the City's Annual Revegetation and Stabilization Bid, whichever is greater. In no instance, will the amount of security be less than one thousand five hundred dollars ($1,500) for residential development or three thousand dollars ($3,000) for commercial development” Concrete Washout Area (CWA) Final Escrow Amount Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence (SF) Vehicle Tracking Control (VTC) Reseeding Amount 4/4/2019 8:34 AM https://d.docs.live.net/0e018cb1e76890ea/Documents/Keefe Civil/25-Meyer Subdivision/Erosion Control Report/Meyer_Escrow.xls 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 13, Sep 10, 2018 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 20, 2015—Oct 21, 2017 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 (Meyer Subdivision) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/18/2019 Page 2 of 3 DS DS DS LEGEND: 4 OF 6 1 2.15 ABBREVIATION LEGEND: PROPOSED POLE BARN TOF = 4949.50' GRADING, DRAINAGE, AND EROSION CONTROL PLAN BMP CONTROLS: SF SP VTC PS PS SP CWA VTC CWA SF SF PS PS PS PS