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� cog BOLTON & <br />0 Z Consulting Engineers & Surveyors <br />m 2035 County Road D East • Suite B • Maplewood, MN 55109-5314 <br />ne e 0. Phone (651) 704-9970 • Fax (651) 704-9971 <br />�rs &sem www.bolton-menk.com <br />June 25, 2015 <br />Patrick Brama <br />Economic Development Manager <br />City of Ramsey <br />7550 Sunwood Drive NW <br />Ramsey, Minnesota 550303 <br />RE: Future Business Park <br />City of Ramsey <br />Project No.: R16.109828 <br />Dear Mr. Brama, <br />Project Background <br />The city of Ramsey is considering the area west of Armstrong Boulevard, East of Plum Street, north of <br />T.H. 10 and south of Alpine Drive, for future development. Storm water retention ponds will ultimately <br />be required to control the runoff from the study area into the COR in accordance with the City's Surface <br />Water Management Plan requirements. The following report summarizes the existing conditions and <br />proposed pond layout options. <br />The site is situated in the Lower Rum River WMO (LRRWMO). Therefore, hydraulics, water quality, <br />rate control, and volume reduction will be considered based on WMO and City requires. For the purposes <br />of this study, preliminary regional stormwater management facilities were design based on assumed land <br />uses and specific design requirements defined by LRRWMO. <br />Hydrologic and Hydraulic Modeling <br />For this study, Bolton & Menk analyzed the existing and proposed conditions using Storm and Sanitary <br />Analysis (SSA) developed by Autodesk, Inc. which utilizes NRCS TR -20 hydrology methodologies to <br />hydrodynamically route stormwater through the drainage system. For this study, the 2 -year, 10 -year, and <br />100 -year rainfall return intervals were analyzed using Atlas 14 rainfall depths and the US Soils <br />Conservation Services (SCS) Type II 24-hour standard rainfall distribution. The corresponding rainfall <br />depths are 2.86", 4.26", and 7.11", respectively. Modeling for future development was tied into existing <br />regional modeling provided by the city. <br />Existing Conditions <br />Drainage from the Lake Itasca outfall is directed toward the study area upstream of Alpine Dr. Overland <br />flow passes through a series of culverts under Alpine Dr., Puma St. NW, and Armstrong Blvd. Flow at <br />the Armstrong crossing is particularly critical as discharge enters the COR area. New development and <br />stormwater management has been designed and constructed around the total contributing flow rate from <br />H:\RAMS\R 16109828\3_Design\C_Reports\Drainage\HydroSubmittal_06262015.docx <br />DESIGNING FOR A BETTER TOMORROW <br />Bolton & Menk is an equal opportunity employer <br />