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CIVIL METHODS,INC. <br />PROFESSIONAL ENGINEERS <br />Saint Paul, Minnesota www.civilmethods.com <br />L AND |W ATER |I NFRASTRUCTURE <br />TECHNICAL MEMORANDUM <br />Date:February 13, 2025 <br />Subject:Idyllvale Shores - Response to 2/10/25 Comments from City of Orono <br />Prepared For:City of Orono <br />Prepared By:Kent Brander, PE <br />A.COMMENTS RECEIVED AND RESPONSES <br />Comments from the City of Orono consultant (Bolton & Menk) on the above-referenced project were <br />received by email attachment. The comments were in a letter addressed to the City of Orono dated <br />February 10, 2025. This Technical Memorandum addresses the comments, which are copied or <br />paraphrased below with responses shown in blue text. <br />Items from 2/10/25 Comments: <br />1.Proposed improvements will require the installation of stormwater runoff management practices to <br />meet Minnehaha Creek Watershed District and NPDES requirements for runoff treatment. The <br />following should be considered regarding stormwater management: <br />a.Per MCWD requirements, the proposed stormwater runoff management system must <br />provide rate control and volume control for the new and fully reconstructed impervious <br />surfaces. <br />As described in the project Stormwater Management Plan (SWMP), several basins are included in the <br />design, to address the Minnehaha Creek Watershed District (MCWD) rate control and volume control <br />requirements. Comments on the SWMP have been provided by MCWD and associated changes are <br />currently being incorporated into the plans. <br />b.Per NPDES requirements, the water quality volume must be treated, calculated as 1” times <br />the sum of the new and fully reconstructed impervious surfaces. If infiltration is prohibited as <br />outlined by NPDES requirements, a wet sedimentation basin or filtration basin may be <br />utilized. <br />Based on soil investigation results and MCWD comments, both infiltration and filtration facilities are <br />included in the stormwater treatment design, as appropriate for site conditions. <br />c.Two filtration basins are proposed to meet MCWD and NPDES requirements. The basins <br />appear to have adequate space to provide runoff treatment, but a number of revisions have <br />been identified by MCWD to meet their requirements. <br />The revisions indicated by MCWD are currently being incorporated into the plans. No significant changes <br />to the overall layout are anticipated. <br />d.Access routes must be provided to all drainage infrastructure to allow for future maintenance. <br />A minimum 8’ wide route must be provided around all basins and ditches accordingly. <br />For each stormwater treatment facility, the designated easements ensure a minimum width of eight feet <br />for maintenance access. <br />162