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4 <br />1! <br />^fD O'- <br />MINNEHAHA C^EEK <br />WATERSHED DISTRICT <br />P.O. Box 387, Wayzata. Minnesota 55391 <br />BOARO of MHWWffI’ James fl. Soensieyi Pres. • John L Thomas • Picharo R. Miner <br />Robsn 0. Ertckson • C. VAJoarw Love • Clarvson Unoiev • Thomas Maoie. Jr. <br />err <br />C-C ■» <br />September 30. lls'U d E [k U <br />Mr. David Squire <br />McCombs Frank Roos Associates, In' <br />15050 - 23rd Ave. No. <br />Plymouth, MN 55441 <br />Re: <br />rocr; 9 <br />Development of Long Lake Wastewater Treatment Plant Site <br />Dear Mr. Squire: <br />As we discussed, the District is concerned that the development of the site which <br />contains the abandoned Long Lake Wastewater Treatment Plant and discharge pond <br />be developed in an environmentally sound manner and in accordance with District <br />rules. The Minnehaha Creek Watershed District has several concerns regarding this <br />site. <br />District rules require that the rate of stormwater nmoff from the site shall not increase <br />as a result of the proposed development. Please note Rule B3(h) specifies that all <br />stormwater rate control facilities shall be located above the projected 100-year <br />frequency flood elevation for the site. This criteria should be analyzed and met for <br />runoff producing events of critical duration with return frequencies of 1, 10 and 100 <br />years. The project shall cause no net decrease in flood storage compacity below the <br />projected 100-year frequency flood elevation, .-^n analysis may be required to <br />determine this elevation. In addition, alteration of any protected water requires a <br />permit from the District under Rule D - Wetland Alteration. Information received <br />from the DNR indicates that the on-site pond is a DNR Protected Wetland. <br />An additional significant concern with this development is that the large on-site pond <br />served as the discharge pond for the Long Lake Sewage Treatment Plant. Sediments <br />in ponds of this type often contain materials detnmental to water quality. The District <br />is concerned that discharge from this site not cause degradation of the waters of the <br />DistricL Water quality information submitted for this project must include the effects <br />of any proposed modifications to the site on Long Lake Creek incluaing the analysis of <br />the affect of potential sediment, suspended solids, nutrients such as phosphorus as well <br />as other chemicals, metals and compounds. As we discussed, the information you have <br />submitted to the District does not fully address these concerns. Some options which you <br />may wish to consider include: eliminate discharge from the on-site pond, removal of <br />sediments from the on-site pond to prevent their discharge, or chemically or physically <br />binding sediments to prevent detrimental affects of their discharge.