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Bremer Bank – St. Anthony July 20th, 2021 1 INTRODUCTION This stormwater management report summarizes the proposed stormwater improvements for the redevelopment of a 0.91-acre parcel in St. Anthony. The site currently sits vacant and is located southwest of the intersection of Kenzie Terrance and Coolidge Street. According to the geotechnical report written by Braun Intertec, the underlying soils of the site consist of SM, SC, ML, and CL soils, and the City considers all areas within the city to be impermeable. The geotechnical report is provided in Appendix A. This project will utilize an underground Stormtech system to meet or exceed the required rate control, volume control and water quality requirements for the local governing agencies. The proposed site improvements for the project will include the construction of a building and drive thru, installation of underground stormwater basin and utilities, and landscaping. New and disturbed green areas will be re-established with sod and landscaping. The project site is under the regulatory authority of the City of St. Anthony (City) and the Mississippi Watershed Management Organization (MWMO). The site was modeled using HydroCAD with the Hennepin County Atlas-14 precipitation depths and NRCS MSE Type III distribution for rate and volume control. The HydroCAD model results for both pre-development and post-development conditions can be found in Appendix B. REGULATIONS The proposed project site is located within the city of St. Anthony, Minnesota and the MWMO. The following rules from the City and Watershed apply: • NURP-level pretreatment is required for all runoff leaving the site as feasible. Providing 60% TP removal and 90% TSS removal will satisfy this requirement. A StormTech (or approved equal) system with an isolator row capable of handling 1.1” of runoff from the site’s impervious surfaces will also satisfy this requirement. • Maintain two feet separation between the Atlas 14 100-year high water elevation and lowest building floor elevation, or one foot of separation between the emergency overflow elevation and the lowest building floor elevation. • Provide stormwater controls such that the critical Atlas 14 1-year, 2-year, 10-year and 100-year storm events for the existing condition peak discharge rates are not increased following site development. • New storm sewer systems shall be designed to accommodate a critical duration Atlas 14 10-year storm event.