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<br />H:\ORNO\_Surface Water Management\MS4 Administration\MCM-5\2_Site Plan Reviews\Idyllvale Shores\Idyllvale_PrePlatReview_2_2025-02-10.docx <br /> <br />February 10, 2025 <br /> <br />City of Orono <br />Attn: Melanie Curtis <br />2750 Kelley Parkway <br />Orono, MN 55356 <br /> <br />RE: Preliminary Plat Application <br /> Idyllvale Shores <br /> Engineering Review #2 <br /> <br /> <br />Dear Melanie: <br /> <br />As requested, I have completed an engineering review of the documents submitted for the above <br />referenced project. Following are my comments for your consideration: <br /> <br /> <br />1. Proposed improvements will require the installation of stormwater runoff management <br />practices to meet Minnehaha Creek Watershed District and NPDES requirements for runoff <br />treatment. The 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 />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 <br />as outlined by NPDES requirements, a wet sedimentation basin or filtration basin may be <br />utilized. <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 />d. Access routes must be provided to all drainage infrastructure to allow for future <br />maintenance. A minimum 8’ wide route must be provided around all basins and ditches <br />accordingly. <br />e. Per City requirements to track TMDLs and reduce loads to meet required Waste Load <br />Allocations, the calculations for Total Suspended Solids (TSS) and Total Phosphorus (TP) <br />loading should be provided. <br />f. Facilities necessary for the ultimate development (street construction, sewer, basins, etc.) <br />should be installed and the site mass-graded at the same time as street construction to <br />ensure all drainage ways, watersheds, and runoff management systems are constructed per <br />the approved Stormwater Management Plan and are sized adequately for proposed <br />improvements. <br />2. Final Plans should include the following: <br />a. Grading, Drainage, and Erosion Control Plan <br />b. Street Construction Plan <br />c. Landscape and Restoration Plan <br />159