05-11-1998 Council Packet - Laserfiche WebLink

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COUNCIL Mht I iNGREQUEST FOR COUNCIL ACTION MAY 11 1998 cmi'croRCNo DATE: May 1, 1998 ITEM NO.: Department Approval: Name Gregory A. Gappa Title Director of Public Services Administrator Reviewed:Agenda Section: Engineer's Report Item Description: Outlet for Mooney Lake ary 9, plans ;t and )NO, f, are n the under days, 11:00 tuncil . An s will , Any en an dered k,bid d this BACKGROUND. The cities of Orono, Medina, and Plymouth and the Minnehaha Creek Watershed District have been approached by residents living on Mooney Lake co.ocemed about high water levels. Mooney Lake does not have a surface outlet and is therefore a landlocked water body. The surface water elevation of landlocked water bodies tends to fluctuate more greatly than if the water body has an outlet. The Minnehaha Creek Watershed District prepared a Mooney Lake water level evaluation in December 1995. The lake level was recorded between May and November 1995, and hi.storical information from 1958 to 1995 was reviewed. Very little historic lake elevation data exists for Mooney Lake. In the 37 years prior to 1995, there are seven lake level readings ranging from approximate low elevation of 983.1 to approximately a high elevation of 988.6. In 1995, the water level ranged between 988 to just over 989. The DNR ordinary high water which is generally considered to be the highest elevation that the lake spent sufHcient time to leave physical evidence upon the land is elevation 988.0. Information in the Mooney Lake water level evaluation indicates that the likelihood of damage to structures around Mooney Lake for a 100 year frequency storm event is very low. There is however potential for damage to trees, yaids, and landscaping and damage to trees has already occurred. Preliminary di;;cu.'..:?ons indicate that the most likely configuration for a Mooney Lake outlet would be a pumping station discharging to the storm sewer proposed to be constructed with the Femdale Road reconstruction. 1impact or capacity of the discharge to the downstream storm water system has not been determined. An engineer feasibility study needs to completed for this proposed outlet. The study should determine: 1. The Feasibility of the project. 2. The preferred route and configuration for the outlet. 3. The estimated cost of the project. 4. The impact on the downstream storm water system. 5. The benefits of the project. COUNCIL ACTION REQUESTED: Recommend that ihe City Council adopt the attached resolution petitioning the Minnehaha Creek Watershed District to prepare an Engineering Feasibility Study for construction of an outlet for Mooney Lake.