2010-11-30_AgendaPacket - Laserfiche WebLink

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GRASS LAKE WATER MANAGEMENT ORGANIZATION TO: Craig Wills FROM: Leonard C. Ferrington Jr., Chair, Grass Lake Watershed Management Organization SUBJECT: DNR Permit request 1971 -1269 (Request for repair of outlet to Wabasso Lake) Leonard C. Ferrington Jr. 366 North Owasso Boulevard Shoreview, MN 55126 Telephone 651 -765 -2461; Fax 612 -625 -5299 29 October 2010 Dr. Mr. Wills, After examining the outflow structure on Lake Wabasso and reviewing the concept for repair of the structure developed Ramsey County, the Board of the Grass Lake Water Management Organization would like to make the following recommendations regarding repair actions. Based upon recent inspections it is clear that the water control device has severe leaks which interfere with its ability to maintain water levels in Lake Wabasso. it is the Boards understanding that leakage around and under the weir has been a longstanding concern by both local residents and past members of the Board of the Grass Lakes Watershed Management Organization. Some local residents have suggested that leakage is related to muskrat burrowing activities, and at least part of the problem may be related to past burrowing. However, it also appears that there could be significant leakage under the structure. In order to restrict leakage around the wing -walls of the weir, the plan by the county to use sheet pile and wire baskets along the margins of the channel from the open -water area of the lake to the weir would be effective to prevent future problems with muskrats. However, there still could be significant leakage under the 12 -inch concrete slab that forms the base of the weir when water levels rise. Consequently, the Board would like to endorse the request by Mr. Tom Petersen (RCD) to add sheet -pile to the lake -side front of the weir structure, and the Board agrees that it should be secured (sub- grade) to the walls of newly installed wing -wall sheet -pile to make sure leakage under the structure in minimized. This will help prevent muskrats from re- focusing their burrowing on the front of the structure and also minimize other leakage under the weir. The Board strongly agrees with Mr. Petersen's statement that this minor addition can significantly increase the functionality and longevity of the weir structure. "The Board also agrees with Mr. Peterson that expediting this project is a reasonable and responsible way to avoid having to work at the site if water levels should increase during late fall or winter. Please call me with any questions and or concerns.