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Ms. Katie Larsen <br />July 6, 2016 <br />Page 2 <br />STORMWATER MANAGEMENT <br />We reviewed the Stormwater Drainage Report for United Properties, dated May 16, 2016 and <br />revised on June 17, 2016 by Plowe Engineering, Inc., and have the following comments: <br />1. The outlet pipe to Clearwater Creek should be replaced with a treatment train concept to <br />provide an additional water quality BMP. An open channel with filtration should be <br />considered. <br />2. Updated existing conditions HydroCAD results were not provided in the June 17, 2016 <br />submittal, however compared to the May 16, 2016 Stormwater Drainage report, the total <br />drainage areas between existing and proposed conditions differs by 1,125,728 square feet. <br />3. The stormwater treatment basins have been separated; however please review the outlet <br />control structures as the HydroCAD models do not reflect the June 17, 2016 plans. <br />4. Please note the proposed drainage areas exhibit shows two subcatchment 4's. <br />FLOODPLAIN <br />1. The project is located within, and impacting, the FEMA 100-year floodplain. <br />Compensatory mitigation will be required at a minimum 1:1 ratio within the same <br />floodplain in which the impacts occur. The applicant shall obtain a Letter of Map <br />Revision and provide the application to City. <br />1. The applicant shall provide an exhibit showing no net fill in the floodplain. <br />2. The proposed crossing over Clearwater Creek will need to accommodate the future <br />sidewalk/trail extension. <br />3. The proposed crossing will require a No -Rise Certificate submitted to the City in order to <br />document no change to the Clearwater Creek floodplain elevations. <br />WETLANDS <br />Rice Creek Watershed District is the LGU to review and approve the wetland delineation and <br />wetland replacement plan. Thus we have not reviewed for the Wetland Conservation Act <br />(WCA). <br />1. The project proposed 0.36 acres of impacts to existing wetlands and it is anticipated that a <br />wetland replacement plan will be required. The applicant will need to receive RCWD <br />approval of wetland impacts and buffers as well as ACOE approval of wetland impacts. <br />2. 21st Avenue is proposed to be a temporary cul du sac ending at the south parking lot. The <br />roadway would be extended down to Cedar Street in the future. As part of the future road <br />K:\02988-200Wdmin\PIw Review 06-20-16\20160706 Engineering Review #2 United Properdes.doox <br />