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HomeMy WebLinkAboutUtility and Drainage SummaryUtility &Drainage Summary Ashmoor Residential Subdivision (PUD) 131st Street & Shelborne Road Carmel, Indiana 46032 Job #: BDX.003 Date: 10 -17 -13 Prepared by: Eric A. Gleissner, P.E. Reviewed by: Brian Cross, P.E. Civil Site GROUP, INC 643 Massachusetts Avenue Suite 200 Indianapolis, IN 46204 Phone: 317- 423 -3305 Fax: 317- 423 -3306 TABLE OF CONTENTS A. Water Service B. Sanitary Sewer Service C. Stormwater Drainage Summary (see calculations for more detailed information) A. Water Service Water service will be provided by the City of Carmel Water - Wastewater Utilities. Water service is available within the existing Shelbourne Estates Subdivision near the southwest corner of the subject site at the connection with Yancey Place. This is an 8" water main which we are proposing to connect to and extend. In addition, there is a 12" water main on the west side of Shelborne Road which we are also proposing a connection to. There is also a 12" water main on the north side of West 131st Street; however, we are not proposing a connection to this main. B. Sanitary Sewer Service Sanitary sewer service will be provided by Clay Township Regional Waste District. There is an existing 8" sewer main within the existing Shelbourne Estates Subdivision near the southwest corner of the subject site at the connection with Yancey Place. Top of Casting Elevation = 912.04 Invert Out Elevation (West) = 903.36 There is also a 12" diameter sewer main located on the south side of West 131st Street adjacent to the subject site. Top of Casting Elevation = 912.60 Invert Out Elevation (West) = 897.06 We are proposing connections to both sewers to serve the proposed development. A stub will be constructed to the southwest along Shelborne Road for future development per direction from Clay Township Regional Waste District. The sanitary sewers have adequate depth and capacity to serve the proposed development. C. Stormwater Drainage Summary This section is intended to be a basic summary of the existing and proposed drainage for the subject site. Please reference the Drainage Calculations for more detailed information. The existing property drains via overland flow to the southwest to an existing 24" RCP storm sewer constructed as part of Shelbourne Estates. The entire subject property is part of the Albert Shaw watershed which drains southwest ultimately outletting into Boone Creek. The site is vacant and is used as agricultural farm land currently planted with corn. A 24 -hour duration storm event was analyzed using the SCS -II rainfall distribution. Basin "EX1" represents the entire 39.59 acre site including the existing right -of -way to the centerline of the road of both 131st Street and Shelborne Road. Per the City of Carmel Stormwater Technical Standards Manual, we will be providing stormwater detention for the fully developed conditions of the right -of -way of both 131st Street and Shelborne Road. Therefore, the allowable release rate will be calculated based on the entire 39.59 acre site to the centerlines of both streets. The following table summarizes the existing runoff rates of the subject site as it exists today: Table 1: Existing Conditions Per the City of Carmel Stormwater Technical Standards Manual, the maximum allowable release rates in the fully developed condition shall be 0.10 cfs for a 10- year storm event and 0.30 cfs for a 100 -year storm event. Therefore, the allowable release rates for this site will be 3.96 cfs and 11.88 cfs for 10 -year and 100 -year storm events respectively. The proposed drainage patterns for the site will remain nearly identical to the existing conditions. A 2.38 +1- acre wet detention pond is being proposed along the western property line to provide stormwater detention and post- construction stormwater quality (BMPs). Per the City of Carmel Stormwater Technical Standards Manual, we are providing stormwater detention for the fully developed conditions of the right -of -way of both 131st Street and Shelborne Road. Basin "PR1" represents the entire 39.59 acre site including the fully developed proposed right -of -way to the centerline of the road of both 131St Street and Shelborne Road. The fully developed curve number was calculated to be 79.0; however, the City of Carmel Stormwater Technical Standards Manual requires that the actual curve number be downgraded to the next poorest classification. Therefore, this results in a downgraded curve number of 84.9 which is what was used in the hydraulic model. DRAINAGE BASIN RUNOFF (CFS) STORM EVENT 24 -Hour Event BASIN EX1 2 -YEAR 25.29 cfs 10 -YEAR 46.75 cfs 100 -YEAR 97.91 cfs Table 1: Existing Conditions Per the City of Carmel Stormwater Technical Standards Manual, the maximum allowable release rates in the fully developed condition shall be 0.10 cfs for a 10- year storm event and 0.30 cfs for a 100 -year storm event. Therefore, the allowable release rates for this site will be 3.96 cfs and 11.88 cfs for 10 -year and 100 -year storm events respectively. The proposed drainage patterns for the site will remain nearly identical to the existing conditions. A 2.38 +1- acre wet detention pond is being proposed along the western property line to provide stormwater detention and post- construction stormwater quality (BMPs). Per the City of Carmel Stormwater Technical Standards Manual, we are providing stormwater detention for the fully developed conditions of the right -of -way of both 131st Street and Shelborne Road. Basin "PR1" represents the entire 39.59 acre site including the fully developed proposed right -of -way to the centerline of the road of both 131St Street and Shelborne Road. The fully developed curve number was calculated to be 79.0; however, the City of Carmel Stormwater Technical Standards Manual requires that the actual curve number be downgraded to the next poorest classification. Therefore, this results in a downgraded curve number of 84.9 which is what was used in the hydraulic model. The following table identifies the release rates from the site, with the proposed improvements, AFTER being routed through the proposed detention facility. STORM EVENT DETENTION POND DISCHARGES (CFS) DETENTION POND STAGE 2 -YEAR 2.15 cfs 908.51' 10 -YEAR 3.77 cfs 909.25' 100 -YEAR 9.38 cfs 910.89' Table 2: Proposed Conditions Proposed 10 -year discharge 3.77 cfs < 3.96 cfs (allowable release at 0.1 cfs per acre for 39.59 acres) Proposed 100 -year discharge 9.38 cfs < 11.88 cfs (allowable release at 0.3 cfs per acre for 39.59 acres) The existing 24" RCP storm sewer constructed as part of Shelbourne Estates has been sized to accommodate the runoff from the proposed development. The storm sewer was constructed at 0.30% which has a calculated capacity of 12.39 cfs with zero head and 17.89 cfs with one foot of head. The maximum discharge from the proposed development during a 100 -year storm event will be 9.38 cfs; therefore, there is more than adequate capacity to accommodate the proposed development.