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Home My WebLink AboutDrainage Calculations 1 1 DRAINA 1 C ALC U LATIO NS COLLEGE PARK CHURCH 1 ADDITIONS RENOVATIONS CARMEL, INDIANA DEVELOPER: ASPEN GROUP 90 Executive Drive, Suite A 1 Carmel, IN 46032 (317) 582 -5100 1 1 DESIGNER: TPG 1 THE SCHNEIDER CORPORATION 411b1 Historic Fort Harrison 8901 Otis Avenue -1 Schneider Indianapolis, IN 46216 -1037 317 826 -71 1 317 826 -7300 Fax March 3 2010 T: \4k \4477 \004 \drainage \drainreport.doc 'c'& 0\103 PR 2 2 2p1� a 00C S 1 1 TABLE OF CONTENTS 1 Drainage Narrative Site Maps Appendix A USGS Map 1 Soils Map Existing Conditions Appendix B 1 CN Value Table Weighted CN Calculations Time of Concentration Calculations 1 Hamilton County Requirements for Rainfall Depths for Various Return Events ICPR Routing Schematic ICPR Input Report 1 ICPR Node Report ICPR Basin Report ICPR Link Report Proposed Conditions Appendix C P PP 1 Weighted CN Calculations Time of Concentration Calculations ICPR Routing Schematic 1 ICPR Input Report ICPR Node Report ICPR Basin Report ICPR Link Report 1 Storm Sewer Design Appendix D 1 Time of Concentration Calculations Hydraflow Reports Post Construction BMP Calculations Appendix E 1 1 1 T: \4k \4477 \004 \drainage \drainrep ort. doc 1 1 DRAINAGE NARRATIVE DESIGN CRITERIA These drainage calculations are based on given data and design criteria as 1 follows: Site location: College Park Church is an existing facility with proposed improvements located on approximately 35.37 acres. The site is part of Section 8, Township 17N, 1 Range 3E, in Hamilton County, Indiana. Specifically, the site is located in the northwest corner of the intersection of 96 Street and Towne Road. 1 Terrain and existing ground condition: The site currently consists of a church with asphalt and gravel parking along with 1 several other buildings including gravel /asphalt access drives to the structures. There are existing storm sewer facilities and a dry detention basin that currently drain the site. The remainder of the site is covered with grass and woods. The overall site has 25' of relief, with elevations ranging from 871 M.S.L. on the peak of a mound in the northeast portion of the site to 846 M.S.L. at the southeast corner of the site where the Fitch Jessup Drain crosses under 96 Street. The majority of runoff from the site is routed through the existing dry detention basin, however there are small portions of the site that drain to the southwest and northeast. According to the Phase 1 Environmental Site Assessment prepared r by August Mack and dated November 20, 2009, no wetlands exist on the site. Adjoining land conditions: North: Single Family Residential/Woods /Grass South: Single Family Residential Subdivision East: Wooded Area West: Single Family Residential Subdivision 1 Soil types: Soils maps from the United States Department of Agriculture, Soil Conservation Service identify Brookston, Miami and Crosby soils on the subject site. Brookston (Br) and Miami (MmB2) are a part of hydrologic group B, while Crosby 1 (CrA) is a part of hydrologic group C. 1 T: \4k \4477 \004 \drainage \drainreport. doc 1 1 Overall Drainage Design: In the existing state, the site primarily drains from the northwest corner of the site toward the southeast. 17.35 acres (PRE- EX -DB) of the site drains to the existing dry detention basin. Included in this watershed is the majority of the gravel parking lot and all of the existing building and asphalt parking lot. A 1.56 acre offsite watershed (OFF -WEST) also drains directly to the existing dry detention basin. 7.06 acres (PRE -DEP) of the site drains to a depressional area located to the north of the mound. When the depressional area fills with runoff, it overflows into a swale and storm sewer that is routed to the existing dry detention basin. A 0.66 acre offsite watershed (OFF- NORTH) also drains directly to the depressional area. The dry detention basin has two outlets to the Fitch and Jessup Drain, one being a 12" RCP and the other is an outlet control structure with an 18" RCP. The 12" RCP is the primary outlet and is at a lower elevation than the outlet control structure. The remaining runoff from the site is currently not being detained. 3.76 acres (PRE -SE) of the site drains directly into the Fitch and Jessup Drain, 4.26 acres (PRE -SW) of the site sheet drains across the west 1 boundary at the southwest corner, and 0.97 acres (PRE -E) sheet drains to the northeast from the site. 1 In the proposed state, additional detention facilities will be required to control the additional runoff created by the site improvements. The existing dry detention basin and its outlet will continue to be utilized along with three additional 1 proposed dry detention basins. All of the detention facilities will be interconnected with the north dry basin being the most upstream facility. The north dry basin will outlet into the west dry basin at the southwest corner of the site. The west dry basin will outlet into the east dry basin, which is southwest of the proposed parking lot. The east dry basin will outlet into the existing dry basin. The north and east dry basins will have outlet control structures that will be utilized for water quality and quantity measures. The majority of the runoff from the site will be routed to the north dry basin. There will still be undetained runoff leaving the site in the proposed state. The watersheds draining directly to the Fitch Jessup Drain and to the southwest corner have been reduced in size and have not had any additional impervious area added to them. The watershed draining to the northeast has been modified, but is similar in size and produces a similar amount of runoff when comparing the proposed to the existing values. Since the existing site already has a large amount of improvements and a detention facility, the existing drainage conditions were modeled in ICPR. The proposed detention facilities were then sized to detain the additional runoff from the proposed improvements. Since runoff from the site should have been detained when the original improvements were made, the proposed detention facilities have been designed so that the proposed release rates will be less than or equal to the existing release rates. The comparison of the existing vs. proposed release rates are shown on the next page. T: \4k \4477 \004 \drainage \drainrep ort. do c 1 1 100 -year Storm Event BNDY-E (Existing) 1.38 cfs BNDY -E (Proposed) 1.86 cfs Negligible BNDY -SE (Existing) 24.00 cfs BNDY -SE (Proposed) 20.57 cfs OK BNDY -SW (Existing) 6.25 cfs BNDY -SW (Proposed) 0.54 cfs OK 10 year Storm Event BNDY -E (Existing) 0.53 cfs BNDY -E (Proposed) 0.88 cfs Negligible BNDY -SE (Existing) 14.39 cfs 1 BNDY -SE (Proposed) 13.43 cfs OK BNDY -SW (Existing) 2.53 cfs 1 BNDY -SW (Proposed) 0.27 cfs OK 2 year Storm Event 1 BNDY -E (Existing) 0.22 cfs BNDY -E (Proposed) 0.47 cfs Negligible BNDY -SE (Existing) 8.34 cfs BNDY -SE (Proposed) 8.33 cfs OK BNDY -SW (Existing) 1.13 cfs BNDY -SW (Proposed) 0.15 cfs OK The discharge rates are met at all locations for each storm event. A table showing pond staging information is shown below. Initial Top of 100 Year Stage Bank Stage Existing Dry Basin 846.90 852.70 851.19 East Dry Basin 851.50 859.00 857.11 West Dry Basin 852.80 859.70 858.10 North Dry Basin 855.00 865.00 860.56 1 Post Construction BMP Design: The dry detention basins will be utilized as the BMPs for this site. The north and east proposed dry detention basins will have outlet control structures to control runoff from the 1" rain event. The release from the north dry detention basin will be controlled by a 30" riser pipe with 1" holes drilled in it to control runoff for water quality. The top of the 1 riser pipe will be open to allow runoff from storms larger than 1" to pass. The release T: \4k \4477 \004 \drainage \drainreport. doc 1 1 1 from the east dry detention basin will be controlled by a 24" riser pipe with 1" holes drilled in it to control runoff for water quality. The top of the riser pipe will be open to allow runoff from storms larger than 1" to pass. Both outlet control structures have been designed so that no more than 50% of the calculated water quality volume has been released in 12 hours since the runoff entered the detention facility, and will also create a 24 to 48 hour emptying time. Both dry basins also have a 5' flat bottom main channel with a longitudinal slope of 0.6 The remaining bottom of the dry basin will slope at a minimum of 2% toward the channel. The vegetation at the bottom of the dry 1 basin should act as a filter for large sediment. References: Design and data methods are based on the following references: 1 1. HERPICC County Storm Drainage Manual 2. Hamilton County Soils Survey 3. ICPR Computer pond routing program 4. 210- VI- TR -55, Second Ed., June 1986 5. Stormwater Technical Standards Manual of Hamilton County, November 2005 Edition 1 6. Indianapolis Stormwater Design and Specifications Manual 7. SCS National Engineering Handbook, Section 4 Overall Watershed: 1 Delaware Creek 1 1 1 1 1 1 T: \4k \4477 \004 \drainage \drainreport. doc 1 1