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HomeMy WebLinkAboutDrainage Report Drainage Calculations TOM WOOD HONDA POWERHOUSE BUILDING REMODEL 3006 East 96th Street Carmel, Indiana 46240 Job #: GCC.004 Report Date: 11-09-23 Revised Date: N/A Prepared by: Eric A. Gleissner, P.E. Reviewed by: Brian S. Cross, P.E. 718 Adams Street Suite E Carmel, IN 46032 Phone: 317-810-1677 TABLE OF CONTENTS Section I: Report A. Project Title B. Project Description C. Permit History D. Zoning Commitments E. Design Method and Criteria F. References G. Existing Conditions H. Proposed Conditions I. Downstream Analysis J. Stormwater Quality Section II: Appendix A. Site Information B. Existing Conditions (exhibits, output data, calculations, etc.) C. Proposed Conditions (exhibits, output data, calculations, etc.) SECTION I: REPORT A. Project Title Tom Wood Honda Powerhouse Building Remodel (3006 East 96th Street) B. Project Description This project is located on the north side of East 96th Street just west of Keystone Avenue in Carmel, Indiana. The subject site is addressed as 3006 East 96th Street. There is an existing 15,265+/- square foot (gross footprint) auto dealership (formerly TruWorth Auto) on the subject site. The overall site is 1.80+/- acres in size (less existing right-of-way); however, the limited site improvements will only be disturbing 0.08+/- acres. The proposed improvements will consist of the installation of a handicap curb ramp, a 900+/- square foot concrete display area to be constructed over existing asphalt, and an enclosure for a dumpster and additional storage also to be constructed over existing asphalt. Two existing curbed areas covered with river rock are also to be removed and paved with asphalt. The existing drainage conditions will remain unchanged with the proposed improvements. These plans and calculations analyze the existing and proposed drainage patterns and will show that the proposed improvements should have no negative effect on drainage conditions in the area. The existing land uses adjacent to the subject site are as follows: North: Business / Commercial (B-3) West: Commercial Use (S-2) South: Commercial (City of Indianapolis) East: Business / Commercial (B-3) C. Design Method and Criteria 1. Soil Type: Soil maps from the United States Department of Agriculture, Soil Conservation Service, identify urban land Miami Silt Loam (UkbA, Ukb2 & YmsA – 100% Site). 2. Design Storm: The 2, 10 and 100-year storm events have been analyzed for both the existing and proposed overall conditions. The Rational Method was used for the existing versus proposed conditions comparison analysis. 3. Overall Watershed: The 1.80+/- acre subject site drains via overland flow into multiple existing surface inlets where the stormwater is intercepted and routed to the south via subsurface storm sewers. The on-site storm sewers discharge into the existing public storm sewer infrastructure within 96th Street. The 32” RCP then flows east ultimately discharging into Carmel Creek. D. References 1. TR55 Stormwater Design Manual. 2. Hamilton County Soil Survey. 3. Highway Extension and Research Project for Indiana Counties (HERPIC). 4. City of Carmel Stormwater Technical Standards Manual. E. Existing Conditions The subject site is addressed as 3006 East 96th Street. There is an existing 15,265+/- square foot (gross footprint) auto dealership (formerly TruWorth Auto) on the subject site along with the associated parking, drainage and utility infrastructure. The overall site is 1.80+/- acres in size (less existing right-of-way) and drains via overland flow into multiple existing surface inlets where the stormwater is intercepted and routed to the south via subsurface storm sewers. The on-site storm sewers discharge into the existing public storm sewer infrastructure within 96th Street. The 32” RCP then flows east ultimately discharging into Carmel Creek. An existing conditions runoff analysis was performed using the rational method. The following table summarizes the maximum runoff rates for the existing conditions basin “EX1” which encompasses the entire subject site: DRAINAGE BASIN RUNOFF (CFS) Basin EX1 2-YEAR 6.16 cfs 10-YEAR 9.05 cfs 100-YEAR 12.56 cfs Table 1: Existing Conditions **Overall Subject Site** F. Proposed Conditions The proposed drainage patterns for the site will remain identical to the existing conditions. The proposed improvements will consist of the installation of a handicap curb ramp, a 900+/- square foot concrete display area to be constructed over existing asphalt, and an enclosure for a dumpster and additional storage also to be constructed over existing asphalt. Two existing curbed areas covered with river rock are also to be removed and paved with asphalt. The limited site improvements will only be disturbing 0.08+/- acres. The selective removal of existing asphalt pavement and replacement with 828 square feet of green space surrounding the proposed dumpster enclosure will actually reduce the existing conditions runoff coefficient. It should be noted that the proposed improvements will reduce the existing conditions runoff coefficient “C” of 0.72 to 0.71 for the proposed conditions of the overall subject site. Therefore, the stormwater runoff will also be reduced. A proposed conditions runoff analysis was performed using the rational method. The following table summarizes the total proposed runoff rates for the proposed conditions basin “PR1” which encompasses the entire subject site: DRAINAGE BASIN RUNOFF (CFS) Basin PR1 EX1 (existing) 2-YEAR 6.07 cfs = 6.16 cfs (existing) 10-YEAR 8.93 cfs = 9.05 cfs (existing) 100-YEAR 12.39 cfs = 12.56 cfs (existing) Table 2: Proposed Conditions **Overall Subject Site** I. Downstream Analysis The overall site is 1.80+/- acres in size (less existing right-of-way) and drains via overland flow into multiple existing surface inlets where the stormwater is intercepted and routed to the south via subsurface storm sewers. The on-site storm sewers discharge into the existing public storm sewer infrastructure within 96th Street. The 32” RCP then flows east ultimately discharging into Carmel Creek. It should be noted that the proposed improvements will reduce the existing conditions runoff coefficient “C” of 0.72 to 0.71 for the proposed conditions of the overall subject site. Therefore, the stormwater runoff will also be reduced. J. Stormwater Quality Section 701.03 of the City of Carmel Stormwater Technical Standards Manual states that projects disturbing less than 1/4 (0.25) acres of land are not required to provide Post-Construction Stormwater Quality Management. The total disturbed area for the proposed improvements will only be 0.08 +/- acres of land. Therefore, additional post-construction stormwater quality measures (BMPs) will not be required for the proposed improvements. SECTION II: APPENDIX A. Site Information Soil Map—Hamilton County, Indiana Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/7/2023 Page 1 of 3442003044200504420070442009044201104420130442015044201704420190442003044200504420070442009044201104420130442015044201704420190575630575650575670575690575710575730575750 575630 575650 575670 575690 575710 575730 575750 39° 55' 42'' N 86° 6' 54'' W39° 55' 42'' N86° 6' 48'' W39° 55' 36'' N 86° 6' 54'' W39° 55' 36'' N 86° 6' 48'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 16N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:881 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 1:15,800. 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: Hamilton County, Indiana Survey Area Data: Version 24, Sep 1, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 15, 2022—Jun 21, 2022 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—Hamilton County, Indiana Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/7/2023 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI UkbA Urban land-Miami silt loam complex, 0 to 2 percent slopes 0.0 2.6% UkbB2 Urban land-Miami silt loam complex, 2 to 6 percent slopes, eroded 1.5 77.0% YmsA Miami silt loam-Urban land complex, 0 to 2 percent slopes 0.4 20.4% Totals for Area of Interest 1.9 100.0% Soil Map—Hamilton County, Indiana Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/7/2023 Page 3 of 3 B. Existing Conditions EXISTING CONDITIONSRunoff CurveCoefficient NumberImpervious Area = 0.90 98 **RooftopOpen Area = 0.10 68.5 **Open Space (Good Condition)Gravel/Stone = 0.85 87.3Impervious Area = 0.85 98 **PavementMiami Silt Loam (UkbA - 3% Site / UkB2 - 77% / YmsA - 20%) Type "B" SoilON SITE (EX1)Impervious Area Open Area Stone Impervious Area Total Total CompositeCompositeRooftop (ft^2) (ft^2) (ft^2) Pavement (ft^2) (ft^2) (Acres) "CN" "C"15265 14496 1739 46859 78359 1.80 92.3 0.72 Overland flowseg. 1 Shallow Concentrated FlowBasin Length S n T_t Length S Paved/Un Vel. T_tT_cname (ft) % (min) (ft) % (P or U) (ft/s) (min)(min)EX1 19 1.00 0.1504200 1.47 P2.46 15 CIVIL SITE GROUP, INC. EXISTING RUNOFF CALCULATION - RATIONAL METHOD PROJECT NAME TOM WOOD HONDA POWERHOUSE PROJECT No. GCC.004 STORM FREQUENCY DESIGN YEAR 2 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA EX1 1.80 0.72 1.30 5 5 4.75 6.16 STORM FREQUENCY DESIGN YEAR 10 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA EX1 1.80 0.72 1.30 5 5 6.98 9.05 STORM FREQUENCY DESIGN YEAR 100 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA EX1 1.80 0.72 1.30 5 5 9.69 12.56 11/08/23 Page 1 C. Proposed Conditions PROPOSED CONDITIONSRunoff CurveCoefficient NumberImpervious Area = 0.90 98 **RooftopOpen Area = 0.10 68.5 **Open Space (Good Condition)Gravel/Stone = 0.85 87.3Impervious Area = 0.85 98 **PavementMiami Silt Loam (UkbA - 3% Site / UkB2 - 77% / YmsA - 20%) Type "B" SoilON SITE (PR1)Impervious Area Open Area Stone Impervious Area Total Total CompositeCompositeRooftop (ft^2) (ft^2) (ft^2) Pavement (ft^2) (ft^2) (Acres) "CN" "C"15265 15324 1338 46432 78359 1.80 92.0 0.71 Overland flowseg. 1 Shallow Concentrated FlowBasin Length S n T_t Length S Paved/Un Vel. T_tT_cname (ft) % (min) (ft) % (P or U) (ft/s) (min)(min)PR1 19 1.00 0.1504200 1.47 P2.46 15 CIVIL SITE GROUP, INC. PROPOSED RUNOFF CALCULATION - RATIONAL METHOD PROJECT NAME TOM WOOD HONDA POWERHOUSE PROJECT No. GCC.004 STORM FREQUENCY DESIGN YEAR 2 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA PR1 1.80 0.71 1.28 5 5 4.75 6.07 STORM FREQUENCY DESIGN YEAR 10 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA PR1 1.80 0.71 1.28 5 5 6.98 8.93 STORM FREQUENCY DESIGN YEAR 100 LOCATION BASIN ACRES COEF. SUM TIME CONC. (min) INT. "Q" = from to AREA sub total "C" CA CA inlet drain total "I" CIA PR1 1.80 0.71 1.28 5 5 9.69 12.39 Page 2