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Home My WebLink AboutPLANETSCALE LIVING - PDP200015 - SUBMITTAL DOCUMENTS - ROUND 4 - DRAINAGE REPORT HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 1 of 9 HCI ENGINEERING A division of HABERER CARPENTRY INC. DRAINAGE REPORT FOR: Planetscale Living – Affordable Housing Project 906 E. Stuart Street, Fort Collins, CO Owner: Planetscale Limited ATTN: Serdar Badem 12933 Regan Lane, Saratoga, CA Serdar.Badem@Gmail.com Engineer Contact(s): HCI Engineering T. Garrett Goodlin, P.E. 621 Southpark Dr., Suite 1600 Littleton, CO 80120 PH: 303-979-3900 FX: 303-278-7814 7/30/2021 Estimated Project Dates: Project Start Date: 10/1/2021 Project Completion Date: 4/30/2022 HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 2 of 9 Table of Contents: I. General Location & Description ................................................................................................................3 A. Project Location .............................................................................................................................. 3 B. Description of Property .................................................................................................................. 3 C. Topographic Data............................................................................................................................ 4 D. FEMA and Flood Zone Data ......................................................................................................... 4 E. Soils Information ............................................................................................................................. 4 II. Drainage Facility Design ............................................................................................................................4 A. Hydrological Criteria ....................................................................................................................... 4 III. Stormwater Management Facility Design .................................................................................................5 A. Stormwater Conveyance Facilities ................................................................................................. 5 B. Easements ....................................................................................................................................... 5 C. Compliance with Standards ............................................................................................................ 5 D. Maintenance Plan ....................................................................................................................... 6 E. Conclusion ....................................................................................................................................... 6 IV. References .................................................................................................................................................6 Appendix – A, Maps & Reference Materials .............................................................................................................7 Appendix – B, Hydrology Calculations ......................................................................................................................8 Appendix – C, Drainage Plan .....................................................................................................................................9 HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 3 of 9 I. General Location & Description A. Project Location The Site, an area consisting of 0.32 acres, is located at 906 E. Stuart Street, Fort Collins, CO, which is more precisely located in a part of Tract 7, East Acres Subdivision, lying in the NE Quarter of Section 24, Township 7 North, Range 69 west of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. The Site is bordered by Stuart Street Right-of- Way to the south, and existing residential land uses to the west, north and east. Refer to the following map. SITE MAP The Site is approximately located at Latitude, 40⁰ 33’ 49” N – Longitude, 105⁰ 03’ 40” W B. Description of Property The Site is currently developed with an existing two-story residence with associated driveway and yard. Site improvements will consist of a proposed Four Unit townhome with associated permeable paver drive and parking, with yard. As part of this development, construction activities will consist of a new structure built on the existing foundation, utility installation, , paving, fine grading and landscaping. In addition to this, the site driveway and parking lot are proposed to be constructed of permeable pavers. The Site disturbed area and construction HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 4 of 9 limits total approximately 0.28 acres. The existing and developed Site and basin percent impervious values are listed in Table 1 below: Table 1 ONSITE % Impervious Existing Site Proposed Site 50.8% (0.32 acres) 40.5% (0.32 acres) C. Topographic Data The General Existing Site Topographic Conditions for The Site are itemized in Table 2 below: Table 2 Description Result Location of Occurrence Highest Elevation 4982 South of Site Lowest Elevation 4980 North of Site Steepest Slope 25% East limits Average Slope 1 - 3% Most of The Site D. FEMA and Flood Zone Data According to the FEMA Flood Insurance Rate Map: Community-Panel No. 08069C0983H, Effective May 2, 2012, The Site is located in Zone X unshaded. These are areas of 0.2% annual chance of flood; areas of 1% annual chance flood with average depths of less than 1 foot or with drainage areas less than 1 square mile; and areas protected by levees from 1% annual chance flood. The Regulatory Flood Elevation adjacent to The Site is coincident with the project survey elevation of 4953 (worst-case scenario). E. Soils Information Soil Classifications for The Site are reported by N.R.C.S. as consisting of Type C soil for 100% of The Site (Santana loam, 1 to 3 percent slopes) Refer to Attachments for the included ‘N.R.C.S. Websoil Survey Report’. With Kw value averaging 0.32, The Site has a high to susceptibility to sheet and rill erosion by water. With a Wind erodibility group of 5 The Site has a low susceptibility to erosion due to wind. II. Drainage Facility Design A. Hydrological Criteria Due to the size of this site, the rational method was used to determine the runoff for the 5-yr and 100-yr storm event. (See Appendix B) The rainfall intensities given in the Urban Storm Drainage Criteria Manual (USDCM) are as follows: TABLE 3 1-HOUR POINT RAINFALL VALUES FOR CITY OF COMMERCE CITY (INCHES) 2-YR 5-YR 10-YR 100-YR 0.83 1.09 1.40 2.86 HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 5 of 9 III. Stormwater Management Facility Design A. Stormwater Conveyance Facilities There are no existing drainage structures or features on the site. Flows are directed east away from the building toward the existing concrete driveway, or west to the existing side yard. Flows then sheet flow to the north or east off the property. These drainage patterns are mimicked in the proposed condition. Flows produced on the west side of the property are directed away from the building to a new landscape swale with underdrain to ensure adequate slope away from the structure. Flows are directed north to the new permeable pavers. Flows produced on the south and east of the building are directed to the permeable pavers where they will either infiltrate or be directed to the north and east. Historic Direct Runoff Comparison The site has been evaluated as a single basin of 0.32 acres. The composite percent impervious of the existing site is 50.8% and the 10-year and 100-year flows are 0.23 & 0.63 CFS, respectively. The composite percent impervious of the proposed site is 40.5% (10.3% less) and the 10-year and 100-year flows are 0.18 & 0.48 CFS (0.05 CFS and 0.15 CFS less), respectively. The change in the Direct Peak Runoff values for The Site for the 5 and 100-year storm events are shown in the following Table. TABLE 4 DIRECT RUNOFF SUMMARY Area Area % Imp. Time of Concentration Runoff Coefficient Direct Basin Runoff Design (Acres) C10 C100 Q10 (cfs) Q100 (cfs) HISTORIC 0.32 50.8% 6.64 0.51 0.69 0.23 0.63 TOTAL PROPOSED 0.32 40.5% 7.60 0.40 0.52 0.18 0.48 B. Easements There is an existing HOA easement directly east of this property, between Spring Meadow Court ROW and The Site. The HOW has stated that it will not allow any construction and/or stormwater work in this area and is also not willing to grant any drainage easements to accommodate any increase in flows. C. Compliance with Standards The proposed Site has been evaluated using the rational method as set forth by UDSCM. Both the 100-yr and 10-yr storms have been evaluated. The stormwater conveyance system has been designed to comply with conveyance methods and capacities. This project will be complying with the Low Impact Development drainage requirements set forth in the City of Fort Collins Stormwater Criteria Manual – LID Implementation Manual. (See Appendix A) The project will comply with both options for the implementation of LID systems, as all new private impervious area will be treated by the proposed permeable pavers. The required detached public sidewalk drains south to the Stuart Street ROW. HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 6 of 9 D. Maintenance Plan The owner will compete a monthly maintenance inspection to clean and remove and trash, debris and vegetation that is restricting or not allowing permeable pavers, landscape areas and underdrains to drain. This will include mowing or trimming of landscaped areas. Any repairs to the grading because of washout and/or sedimentation will be removed. E. Conclusion The proposed project has been analyzed utilizing the City of Fort Collins Stormwater Criteria Manual. This drainage letter and associated calculations are limited to the project shown by the attached Drainage Plan. Based on the above findings and attached calculations HCI Engineering finds the proposed development to be in compliance with the drainage criteria set forth in Report 1. No negative impacts are anticipated as a result of this development to adjacent properties or downstream. Sincerely, T. Garrett Goodlin, P.E. HCI Engineering IV. References 1. City of Fort Collins Stormwater Criteria Manual (December 2018), by The City of Fort Collins. 2. Drainage Criteria Manual (Volume 1, 2 & 3), by Mile High and Flood Control District, current versions. 3. FEMA website Flood Insurance Rate Maps. 4. USDA, Web Soil Survey, Soil Map Data. HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 7 of 9 Appendix – A, Maps & Reference Materials • FEMA Firmette • NRCS Soil Map • NRCS Soil Data • CFCSCM Excerpt o Low Impact Development o Runoff Coefficients o Percent Impervious Values 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 7/29/2021 at 11:43 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°3'59"W 40°34'3"N 105°3'21"W 40°33'36"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 Soil Map—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/29/2021 Page 1 of 3449029844903054490312449031944903264490333449034044903474490354449029844903054490312449031944903264490333449034044903474490354494808494815494822494829494836494843494850 494808 494815 494822 494829 494836 494843 494850 40° 33' 50'' N 105° 3' 40'' W40° 33' 50'' N105° 3' 38'' W40° 33' 48'' N 105° 3' 40'' W40° 33' 48'' N 105° 3' 38'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 10 20 40 60 Feet 0 4 8 16 24 Meters Map Scale: 1:284 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 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 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/29/2021 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 95 Satanta loam, 1 to 3 percent slopes 0.4 100.0% Totals for Area of Interest 0.4 100.0% Soil Map—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/29/2021 Page 3 of 3 RUSLE2 Related Attributes This report summarizes those soil attributes used by the Revised Universal Soil Loss Equation Version 2 (RUSLE2) for the map units in the selected area. The report includes the map unit symbol, the component name, and the percent of the component in the map unit. Soil property data for each map unit component include the hydrologic soil group, erosion factor Kf for the surface horizon, erosion factor T, and the representative percentage of sand, silt, and clay in the mineral surface horizon. Missing surface data may indicate the presence of an organic layer. Report—RUSLE2 Related Attributes Soil properties and interpretations for erosion runoff calculations. The surface mineral horizon properties are displayed or the first mineral horizon below an organic surface horizon. Organic horizons are not displayed. RUSLE2 Related Attributes–Larimer County Area, Colorado Map symbol and soil name Pct. of map unit Slope length (ft) Hydrologic group Kf T factor Representative value % Sand % Silt % Clay 95—Satanta loam, 1 to 3 percent slopes Satanta 90 200 C .32 5 43.0 39.0 18.0 Data Source Information Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 15, Jun 9, 2020 RUSLE2 Related Attributes---Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/29/2021 Page 1 of 1 (From Fort Collins Stormwater Criteria Manual - 6.0 Low Impact Development) This Section of this Chapter presents information that is specific to the City of Fort Collins and may be a significant deviation from the information presented in the UDFCD Manuals. Utilizing UDFCD methodologies for Low Impact Development (LID) designs may not be accepted by FCU. In February 2013, Fort Collins City Council adopted Ordinance No. 152, 2012, to incorporate provisions implementing LID principles; with the goal to declare that the purpose of the City Stormwater Utility is to provide an integrated, sustainable stormwater management program that reflects the community’s values of protecting and restoring the City’s watersheds. This was subsequently modified and updated in January 2016 with Ordinance No. 007, 2016 to allow for some added flexibility in the implementation of the LID policy. Reference: Both the initial LID ordinance, Ordinance No. 152, 2012, and the subsequent ordinance, Ordinance No. 007, 2016, can be found on the City of Fort Collins website. LID is simply defined as an integrated, sustainable stormwater management program that requires a distributed, closer to the source stormwater runoff control that simulates natural processes and relies mainly on filtration and infiltration to locally treat and manage stormwater runoff. Integration of LID systems into the drainage design is required for all development projects in order to comply with the City’s policies on LID, the requirements of this Manual, the City Code and the Land Use Code. LID systems provide a higher degree of stormwater quality treatment than that provided with standard water quality design. 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 all newly added or modified impervious area must be treated by LID techniques. Impervious surfaces are defined as hardscape surfaces that do not allow stormwater to infiltrate into the ground. Impervious surfaces include asphalt and concrete surfaces, concrete curbs, gutters, sidewalks, patios and rooftops. (Impervious surface areas must be assumed for single family residential lots when overall impervious areas are being determined for residential developments. The assumed areas must then be included in LID calculations.) “Added” impervious area stated in the two options above is further defined as existing vegetation (or pervious) areas becoming hardscape (or impervious) areas. “Modified” impervious area stated in the two options above is further defined as existing impervious areas on an existing site being removed and replaced with other impervious surfaces through a redevelopment process (i.e. existing asphalt surface becoming a rooftop surface). Mill and overlay of asphalt areas is not considered a “modified” impervious area. “Paved” areas, as stated in option 1 above are generally considered to be private vehicle use areas only. Reference: Refer to the City of Fort Collins LID Implementation Manual in Appendix C for detailed information and requirements on LID systems. (From Fort Collins Stormwater Criteria Manual - 6.2 Permeable Pavement) The term “permeable pavement” is a general term to describe any one of several pavement systems that allow infiltration of water into the layers below the pavement through openings within the pavement surface. Use of permeable pavements is an accepted Low Impact Development (LID) practice in Fort Collins and is often used in combination with other BMPs to provide full treatment and slow release of the WQCV. In addition, there are some installations in Fort Collins that have also been designed with an outlet control and increased depth of aggregate material in order to provide quantity detention in excess of the water quality (80th percentile) storm event. Design considerations for permeable pavement systems are presented in the LID Implementation Manual, included in Appendix C. Included here are some general design requirements applicable for all types of LID system designs in Fort Collins. • Overall added or modified impervious areas that amount to less than 1000 square feet (< 1000 sf) on a site will not require LID system treatment for water quality. • For development sites that are adding or modifying 1000 square feet of imperviousness or more (≥ 1000 sf) are required to implement LID system treatment at the site. The LID system is allowed to treat existing imperviousness in exchange for the newly added imperviousness if the surface character is similar (e.g. existing pavement may be treated in lieu of newly added rooftop) • For single-family residential developments, LID must be placed in tracts or common areas for ownership and maintenance by the HOA. LID systems installed as part of the development requirement shall not be placed on single-family lots. • LID is not required for private, single-family residential improvement projects that are not a part of a larger subdivision project. (i.e. an existing lot in an older part of Fort Collins that is being re-built) FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.2 Runoff Coefficients Page 4 3.2 Runoff Coefficients Runoff coefficients used for the Rational Method are determined based on either overall land use or surface type across the drainage area. For Overall Drainage Plan (ODP) submittals, when surface types may not yet be known, land use shall be used to estimate flow rates and volumes. Table 3.2-1 lists the runoff coefficients for common types of land uses in the City. Table 3.2-1. Zoning Classification - Runoff Coefficients Land Use Runoff Coefficient (C) Residential Urban Estate 0.30 Low Density 0.55 Medium Density 0.65 High Density 0.85 Commercial Commercial 0.85 Industrial 0.95 Undeveloped Open Lands, Transition 0.20 Greenbelts, Agriculture 0.20 Reference: For further guidance regarding zoning classifications, refer to the Land Use Code, Article 4. For a Project Development Plan (PDP) or Final Plan (FP) submittals, runoff coefficients must be based on the proposed land surface types. Since the actual runoff coefficients may be different from those specified in Table 3.2-1, Table 3.2-2 lists coefficients for the specific types of land surfaces. 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 HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 8 of 9 Appendix – B, Hydrology Calculations • Rational Calculations o Percent Impervious o Time of Concentration o Direct Runoff 10-Year Storm o Direct Runoff 100-Year Storm o Direct Runoff Summary & routed Runoff Summary Project:906 E. Stuart Street Surface % Imp.C2 Value C5 Value C10 Value C100 Value Project Number:21_23 Paved Streets 100%0.83 0.86 0.87 0.89 Date:7/30/2021 Roofs 90%0.74 0.77 0.80 0.85 Lawns, clayey soil 2%0.01 0.05 0.15 0.49 Permeable Pavers 40%0.29 0.32 0.38 0.61 Soil Type: C & D Sub-basin I.D. Formula: [(Area)(C Value)+(Area)(C Value)+(Area)(C Value)]/(Total Area) Paved Roof Landscape Pavers Existing Conditions 5267 1865 6806 0 13938 50.8%0.42 0.45 0.51 0.69 Proposed 3647 2116 4531 3644 13938 40.5%0.33 0.36 0.40 0.52 C10 C100 Surface Type Area (S.F.) HCI ENGINEERING A division of HABERER CARPENTRY INC. NRCS Hydrologic Soil Type (Per NRCS Web Soil Survey) Basin I.D.Total Area (S.F.)% Impervious C2 C5 Values per Figures 6-2 in Runoff Chapter of USDCM for Type C Soils Project: Project Number: Date: Final tc Basin I.D.AREA (Ac)C5 Length (ft) SLOPE (%)ti Length (ft) SLOPE (%)Cv Vel. (FPS)tt COMP tc Total Length Ft tc = (26-17i)+Lt/(60(14i+9)St^(1/2))Min Existing Conditions 0.32 0.45 65 3.0 6.64 0 1.0 20 2.0 0.00 6.64 65 17.36 6.64 Proposed 0.32 0.36 65 3.0 7.60 0 1.0 20 2.0 0.00 7.60 65 19.12 7.60 Table RO-2—Conveyance Coefficient, Cv 2.5 5 7 10 15 20 Short pasture and lawns Nearly bare ground Grassed waterway Paved areas and shallow paved swales Conveyance Coefficient, K HCI ENGINEERING A division of HABERER CARPENTRY INC. TIME OF CONCENTRATION Type of Land Surface Heavy meadow Tillage/field 906 E. Stuart Street 21_23 7/30/2021 Initial / Overland Time (ti) Travel Time (tt) tc Check (Urbanized Basins)Basin Data Project:906 E. Stuart StreetProject Number:21_23Date:7/30/2021AreaAreaRunofftcC x AIntensity (I)QDesign PointDesign(ac)Coeff(min)(AC)in/hr(cfs)Existing Conditions0.320.516.640.161.400.23Proposed0.320.407.600.131.400.181-Hour Rainfall Depths for Design StormsDesign Storm2-Year5-Year10-Year100-YearDepth (in)0.831.091.402.86Per NOAA Rainfall DataHCI ENGINEERING A division of HABERER CARPENTRY INC. DIRECT RUNOFF 10-YR STORM Project:906 E. Stuart StreetProject Number:21_23Date:7/30/2021AreaAreaRunofftcC x AIntensity (I)QDesign PointDesign(ac)Coeff(min)(AC)in/hr(cfs)Existing Conditions0.320.696.640.222.860.63Proposed0.320.527.600.172.860.481-Hour Rainfall Depths for Design StormsDesign Storm2-Year5-Year10-Year100-YearDepth (in)0.831.091.402.86Per NOAA Rainfall DataHCI ENGINEERING A division of HABERER CARPENTRY INC. DIRECT RUNOFF 100-YR STORM Project: 906 E. Stuart StreetProject Number: 21_23Date: 7/30/2021AreaArea% Imp.Design(Acres)C10 C100Q10 (cfs)Q100 (cfs)Existing Conditions0.3250.8%6.640.510.690.230.63Proposed0.3240.5%7.600.400.520.180.48HCI ENGINEERING A division of HABERER CARPENTRY INC. Runoff Coefficient Direct Basin RunoffDIRECT RUNOFF SUMMARYTime of Concentration HCI Engineering, - 621 SouthPark Dr., Suite 1600, Littleton CO, 80120 - 720-252-3484 Page 9 of 9 Appendix – C, Drainage Plan SS M CO CO 80.75 80.75 80.51 80.24 MATCH EX. 4980.17 MATCH EX. 4980.01 MATCH EX. 4980.22 80.63 81.68 80.63 81.737.4%7.4%6.0%23.9% 1.1% 0. 5% 0. 5% 0. 5%0.5%3.6%0.8%1.5%FFE = 4980.75 80.27 80.36 80.66 81.6881.57 MATCH EX. 4981.62 MATCH EX. 4981.55 1.5%80.66 81.65 81.58 81.65 MATCH EX. 4981.7081.68 MATCH EX. 4981.64 MATCH EX. 4981.65 MATCH EX. 4981.09 MATCH EX. 4980.05 MATCH EX. 4980.12 MATCH EX. 4980.15 80.21 80.59 80.74 80.75 80.75 80.69 80.69 80.69 80.69 80.6980.69 80.69 80.59 80.73 81.72 80.70 80.75 80.7480.74 80.7480.7480.74 80.74 80.70 4981 1.5%1.1%1.3%1.4%1.4%7.4%0.5%0.5%0.9%0.1%0.1%0.3%1.1%1.6% 0.3%7.4%N REVISIONS: Drawn By: Sheet Sheet Name: No.Date:Description:FILENAME: J:\2021\21_23 906 e. stuart st\CAD\Plans\21-23 - CD - GRADING PLAN.dwg PLOTDATE: 2021-07-30 Checked By: Date Issued: Project No: CALL 811 2-BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. Know what's below, Call before you dig. UTILITY PLANS PLANETSCALE LIVING - AFFORDABLE HOUSING PROJECT A PART OF TRACT 7, EAST ACRES LYING IN THE NORTHEAST 1/4 OF THE NORTHEAST 1/4 OF SECTION 24, TOWNSHIP 7 NORTH, RANGE 69 WEST OF THE 6TH P.M., COUNTY OF LARIMER, STATE OF COLORADO 906 E. STUART ST., FORT COLLINS COLORADO UTILITY PLANSPLANETSCALE LIVING - AFFORDABLE HOUSING PROJECT906 E. STUART ST., FORT COLLINS, CONumber: A DIVISION OF HABERER CARPENTRY INC. 621 SOUTHPARK DR., SUITE 1600 LITTLETON CO, 80120 PHONE: (303) 979-3900 INFO@HABERERGROUP.COM HCI 21_23 1 07.30.21 1ST SUB 7/30/2021 KZH TGG N 30'20'10'0' SCALE: 1" = 10' GRADING PLAN C2.1 DRAINAGE LEGEND DRAINAGE BASIN FLOW ARROW BASIN ID C100AREA (AC) C10 MAJOR BASIN BOUNDARY B3-6 2.8 0.47 0.76 PRO. 0.32 0.40 0.52 XXXX 5421 5420 XXXSLOPE MAJOR CONTOUR MINOR CONTOUR SPOT ELEVATION