06-28-1999 Council Packet - Laserfiche WebLink

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.r REQUEST FOR COUNCIL ACTION COf JNJCIL meeting JUN 2 Q 1999 Ui IY onuivu DATE: June 28, 1999 ITEM NO.: // Department Approval: Name Gregory A. Gappa Title Director of Public Services Administrator Reviewed:Agenda Section: Engineer’s Report Item Description: Mooney Lake Outlet Mooney Lake is located in the far northea«;tem part of Orono with portions of the lake in the Cities of Plymouth and Medina. The lake is 118 acres in size and does not have a natural outlet. A pumping station would be required to provide an outlet to the lake. Because the lake does not have an outlet, there is a concern about rising water levels in the lake. Residents from the three Cities have been working for the last several years to find a solution to the rising water levels. The only Orono resident on Mooney Lake is Doug Dayton. On May 1,1998, the City Council approved a resolution petitioning the Minnehaha Creek Watershed District to complete a feasibility study for this project. The feasibility study has been completed by Bonestroo Engineers. Study Results In 1976 the Minnesota Department of Natural Resources assigned an Ordinary High Water Level (OHWL) of988.0 to the lake. The lowest water elevation of record was 983.1 in 1961. 'fhe highest recorded level was 989.37 recorded on May 26, 1996. Over the past twenty years, the lake has been expieriencing relatively high water levels. High water elevations have been causing damage to trees, yards and landscaping. According to a citizen's report in 1996, over 115 six-inch diameter trees are now under water and are either dying or dead. Over 65 twelve-inch diameter trees and ten 24-36 inch diameter trees are now under water. Flood risk to residential structures is low. The walkout elevation for the lowest structure next to the lake on the north side was 992.85 or 3.48 feet above the highest historical water surface elevation recorded for the lake. The entire drainage district is almost fully developed so great increases in future water levels are not likely. The watershed area of the lake is relatively small compared to the surface area of the lake and infiltration and evaporation appear to limit lake level rises. The feasibility study identified four options. City staff preferred Option 1. This option includes a pumping station on Doug Da>lon's property with piping south and east to the County Road 6/North Femdale Road intersection. A connection would then be made to the new storm sewer system in