3 PCSR 06-10-1993 - Laserfiche WebLink

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�1VIt D BAR 1 bx ��nn��STATEnnUVEOF UVJOO irL.a DEPARTMENT OF NATURAL RESOURCES • 500 LAFAYETTE ROAD • ST. PAUL, MINNESOTA • 55155-40 10 DNR INFORMATION (612) 296-6157 March 15, 1993 Stephen Rohlf Elk River Building & Zoning Administrator 720 Dodge Avenue Elk River, MN 55330 RE: Elk Park Center Environmental Assessment Worksheet (EAW) Dear Mr. Rohlf: The Department of Natural Resources (DNR) has reviewed the EAW for the Elk Park Center project. We offer the following comments for your consideration. Item l lb should have indicated that the Natural Heritage Program has identified a significant natural mixed oak forest community in the NE 1/4 section 27, T33N, R26W, which is within one mile of the Elk Park Center project. We have attached a copy of an earlier correspondence with the Natural Heritage Program for your information. Item 12 states, "A portion of the storm water will be routed east...to wetlands which are proposed • to be designated as a city storm water ditch system." The unrestricted and untreated discharge of stormwaters into a natural wetland is generally opposed by the DNR. This use of wetlands as a stormwater treatment pond is not advised and we recommend the construction of on-site sedimentation ponds (with skimmers where needed) for stormwater treatment and retention. The use of natural wetland systems to treat urban runoff degrades and eventually destroys valuable wetland habitat through sedimentation, contamination, and increased nutrient loading. We will review this aspect of the project during the federal permitting process and we will likely recommend denial of the use of protected wetlands for this purpose. Item 12 also states, "The water surface elevation of the wetlands east of the site will be temporarily raised approximately 5.5 feet by the runoff of the project during a 100-year storm (event)." The information provided in Item 12 is insufficient to determine the overall project impacts to the wetland in question. The EAW should include an evaluation of expected changes in water surface elevations for 1, 5, and 10-year storm events to allow a more accurate appraisal of project impacts. The developer should be required to construct properly sized sediment basins and retention ponds to prevent the 5.5 foot "bounce"which is expected to occur for large scale events. Large fluctuations in water levels negatively impact nesting birds and permanent changes in the water level regime can change the character of vegetation found in wetlands to the detriment of the existing natural community. The proposed project could benefit, harm, or have minimal effects on the wetland in question and further information is required to make this determination. The appropriate erosion control Best Management Practices (BMPs) should be followed during construction activity. Every effort should be taken to minimize sedimentation and erosion during construction. Proper silt fences and floating silt curtains should be used during construction and • for 72 hours after construction activity ceases. We also recommend the mulching and seeding of all disturbed areas within 72 hours of project completion; the AN EQUAL OPPORTUNITY EMPLOYER