11-17-2025 - Agenda Packet Planning Commission - Full Packet

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MINNEHAHA CREEK QUALITY OF WATER WATERSHED DISTRICT QUALITY OF LIFE rip rap along the shoreline. It would be helpful for you to provide photographs of other examples with this design and a scaled typical detail to understand more specifically the proposed configuration. We also discussed that, as solid piers extending 4-5 feet into the lake, these would appear to constitute work within the public waters subject to Minnesota Department of Natural Resources (DNR) regulatory jurisdiction. To support your application process, MCWD staff would be willing to participate in a meeting with the DNR Area Hydrologist to review the proposed specifications of the steps and piers, and to determine the most appropriate and permittable direction for both. Depending on the proposed shoreline design, your team may also need to submit a preconstruction notification to the United States Army Corps of Engineers (USACE) for review under Nationwide Permit No. 13 for Bank Stabilization. This may be necessary if the project involves 1) discharges of dredged or fill material into special aquatic sites; or (2) is in excess of 500 feet in length; or (3) will involve the discharge of dredged or fill material of greater than an average of one cubic yard per running foot as measured along the length of the treated bank, below the OHW. We offer these notes regarding DNR and USACE permitting as informal input. You should, of course, confer directly with those agencies to confirm their jurisdiction and requirements. Stormwater Management Rule We also discussed the design concern relating to the stormwater filtration basin and the presence of shallow groundwater adjacent to the lake. The County advised that it is revising the basin design for purposes including meeting state NPDES and MCWD requirements for separation of the basin bottom from groundwater. For example, as we discussed, the basin noted by cross section B-B in the plans cannot be utilized because runoff would not pass through the full sand layer before mixing with groundwater. The project team advised that it believes the other stormwater basins can be upsized to avoid the area close to the lake with separation difficulties but if further treatment is necessary to meet volume control requirements, options include expanding upgradient basins and capturing, for treatment, runoff from offsite impervious surface that is currently untreated. We understand that the current proposal includes an impermeable liner to maintain separation from groundwater. MCWD staff understands your reasoning for the current configuration, but after further internal discussion, we request that you make every feasible effort to set the liner at or above the OHW. This limits the risk of reduced system functionality and potential uplift from water beneath the liner and meets design requirements without complication. If this placement conflicts We collaborate with public and private partners to protect and im prove land and water for current and future generations. ....................................................................................................................................................................................... _...._ _..____..._ --_ _.. _ _ _ _. _ _..____ __._..__ .. _. _...__. _ _..____ _...--- ...................................................................................................................................................................................... . ...................................................................................................................................................................................... . 15320 Minnetonka Boulevard, Minnetonka, MN 55345 • (952) 471-0590 • Fax: (952) 471-0682 • www.minnehahacreek.org 102