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Home My WebLink AboutDrainage SummaryDrainage Summary Dunkin Donuts C -Store /PetSuites Commercial Development 9800 9802 North Michigan Road Carmel, Indiana 46032 Job HHR.001 Date: 03 -16 -12 Prepared by: Eric A. Gleissner, P.E. Reviewed by: Brian Cross, P.E. STE 9 FO: 9 f No. o PE10403858 STATE OF W 8 1`'•.DIANa %O 111111 N 1/ C iviI site GROUP, INC 643 Massachusetts Avenue Suite 200 Indianapolis, IN 46204 Phone: 317 -423 -3305 Fax: 317 -423 -3306 Section 1: Report A. Project Title B. Project Description C. Design Method and Criteria D. References E. Existing Conditions F. Proposed Conditions G. Stormwater Quality Section 11: Appendix TABLE OF CONTENTS A. Site Information B. Existing Conditions (Exhibits, Calculations, etc.) C. Proposed Conditions (Exhibits, Calculations, etc.) SECTION I: REPORT A. Project Title Dunkin Donuts C -Store PetSuites Commercial Development (9800 9802 North Michigan Road) B. Project Description This project is located on the west side of North Michigan Road (U.S. 421) at the intersection with West 98 th Street in Carmel, Indiana. The site consists of two (2) parcels totaling 3.56 acres in size. The site is currently vacant and was previously occupied by single family residences. The proposed improvements will consist of two new commercial buildings, utility and drainage infrastructure, and new hard surface for parking and ingress egress. The site has been master planned for two additional buildings to be built in the future. A dry detention basin has been designed to significantly reduce the runoff in the developed condition from what is currently discharging in the existing condition. These plans and calculations analyze the existing and proposed drainage patterns and will show that the proposed improvements will have no negative effect on drainage conditions in the area. The existing land uses adjacent to the subject site are as follows: North: Commercial Office (Self Storage) West: Vacant (fill site) South: Commercial Office East: Commercial Office C. Design Method and Criteria 1. Soil Type: Soil maps from the United States Department of Agriculture, Soil Conservation Service, identify Brookston Silty Clay Loam (Br 16% Site) and Crosby Silt Loam (CrA 84% 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 in pipe sizing calculations. Hydrology Detention sizing was performed using the SCS -II 24 -hour rainfall distribution and ICPR computer software. 3. Overall Watershed: The existing site drains via overland flow into the storm sewer system in Michigan Road (U.S. 421). The stormwater ultimately makes its way to Crooked 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 comprised of two (2) parcels previously occupied by single family residences. The homes have been demolished and the 3.56 acre site is currently vacant. The existing property generally drains via overland flow in two directions. The east half of the site drains east into Michigan Road (U.S. 421) where it is intercepted by the existing storm sewer system. The west half of the site drains to the west to the back half of the property and adjacent properties where there is currently no drainage outlet (see attached exhibit "EX1"). The proposed discharge for the entire site in the developed condition will be an existing curb inlet and 18" storm sewer on the west side of North Michigan Road where the existing basin "EX1" currently discharges. Therefore, only the basin "EX1" discharges will be used for comparison of the maximum allowable release rate for the developed site. The curb inlet and 18" storm sewer tie directly into an existing 48" storm sewer trunk line flowing south beneath Michigan Road. A 24 -hour duration storm event was analyzed using the SCS -II rainfall distribution. The following table summarizes the maximum existing discharge rates for the subject site: Table 1: Pre Developed Conditions DRAINAGE BASIN RUNOFF (CFS) Basin EX1 EX2 1 -Hour Event 2 -YEAR 0.75 cfs 1.77 cfs 10 -YEAR 1.77 cfs 4.29 cfs 100 -YEAR 4.55 cfs 11.16 cfs E. Existing Conditions The subject site is comprised of two (2) parcels previously occupied by single family residences. The homes have been demolished and the 3.56 acre site is currently vacant. The existing property generally drains via overland flow in two directions. The east half of the site drains east into Michigan Road (U.S. 421) where it is intercepted by the existing storm sewer system. The west half of the site drains to the west to the back half of the property and adjacent properties where there is currently no drainage outlet (see attached exhibit "EX1"). The proposed discharge for the entire site in the developed condition will be an existing curb inlet and 18" storm sewer on the west side of North Michigan Road where the existing basin "EX1" currently discharges. Therefore, only the basin "EX1" discharges will be used for comparison of the maximum allowable release rate for the developed site. The curb inlet and 18" storm sewer tie directly into an existing 48" storm sewer trunk line flowing south beneath Michigan Road. A 24 -hour duration storm event was analyzed using the SCS -II rainfall distribution. The following table summarizes the maximum existing discharge rates for the subject site: Table 1: Pre Developed Conditions F. Proposed Conditions A slightly different version of this project was previously submitted in November of 2010. The previous layout proposed two future commercial buildings on the east half of the site in addition to the PetSuites building on the rear (west) half of the site. The future commercial buildings have been replaced by a single smaller two tenant building. In addition, the PetSuites building has been shifted roughly 20 feet east towards Michigan Road. This increased the amount of pervious surface as well as increased the area for detention by roughly 32 The proposed improvements will consist of the two new commercial buildings, utility and drainage infrastructure, and new hard surface for parking and ingress egress. The proposed drainage patterns for the site will remain nearly identical to the existing. A dry detention basin will be constructed to significantly reduce the runoff rate of stormwater leaving the site. A Downstream Defender 6' diameter hydrodynamic separator structure along with a Snout oil /water separator will be specified to address the stormwater quality requirements. The overall subject site is 3.56 acres in size allowing a maximum release rate of 0.36 cfs and 1.07 cfs for the 10 -year and 100 -year storm events respectively. This is substantially less than the 1.77 cfs (10 -year) and 4.55 cfs (100 -year) that is currently discharging from the site into the existing storm sewer system in Michigan Road. We are proposing to install a conventional storm sewer outlet with a two tier control structure to limit the discharges. The outlet will connect to an existing curb inlet and 18" storm sewer on the west side of North Michigan Road which then ties directly into a 48" diameter storm sewer trunk line flowing south. An emergency overflow weir will be installed on the south end of the proposed dry detention pond. The overflow route would then go east along the south property line towards Michigan Road. Both the outlet structure itself and the first downstream structure will be designed with open grate castings that can also serve as emergency overflows should the outlet structure fail or become clogged. The release rates from the developed site will be significantly less than in the existing condition; therefore, this project should have no negative effects on drainage patterns in the area. G. Stormwater Quality An offline Downstream Defender 6' diameter hydrodynamic separator will be proposed to address the Stormwater Quality requirements. In addition, a Snout oil /water separator will be proposed on the BMP diversion structure with a 2' sump prior to discharging into the dry detention basin. Based on the new City of Indianapolis Stormwater Quality Treatment Unit (SQTU) Selection Guide, this particular structure has a maximum treatment flow capacity of 3.58 cfs. The required treatment flow rate was previously calculated based on the CNwq at 3.49 cfs per the City of Carmel Stormwater Technical Standards Manual. Therefore, the Downstream Defender 6' diameter structure is an ideal fit for this application. With the removal of impervious surface from the previous design, the required treatment flow rate will only decrease. SECTION 11: APPENDIX A. Site Information 00202440810244061024404102440210244001024408002440600244 ''15 '31 °68''15 '31 °68 ''0 '41 °68''0 '41 °68 00202440810244061024404102440210244001024408002440600244 B. Existing Conditions Advanced Interconnected Channel & Pond Routing (ICPR Ver 2.20) [1] Copyright 1995, Streamline Technologies, Inc. ********** Basin Results Comparisons **************************** Simulation Name Time Max Flow Max Runoff Volume Runoff Volume (hrs) (cfs) (in) (cf) ----------------------------------------------------------------- *** Basin Name: EX1 2YHR-24R 12.04 0.75 0.55 1966 10YR24HR 12.02 1.77 1.25 4434 100Y24HR 12.02 4.55 3.22 11454 *** Basin Name: EX2 2YHR-24R 12.05 1.77 0.55 5193 10YR24HR 12.05 4.29 1.25 11715 100Y24HR 12.03 11.16 3.22 30262 C. Proposed Conditions