11-19-2018 Planning Commission Packet

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CMP Part 3A. Environmental Protection Plan CMP PART 3(A) ENVIRONMENTAL PROTECTION PLAN The presence and character of relatively undisturbed natural resource areas including lakes, marshes, wetlands, and woodlands is a major factor affecting the character of Orono. LAKE MINNETONKA • Lake Minnetonka is the single most significant natural feature in Orono and in the entire western part of Hennepin County.Lake Minnetonka,as shown on Map 3A-1,is actually a series of separate lakes or"bays" interconnected by narrows or channels. The outlet of Lake Minnetonka is at Gray's Bay in the City of Minnetonka, where it discharges to Minnehaha Creek which eventually flows into the Mississippi River. • Lake Minnetonka has substantial public value as a recreational asset, as an environmental resource and as a setting for private residential development. • Lake Minnetonka is dependent upon watershed runoff for all replenishment. bake Minnetonka is not fed by any spring or river inlet. All water is received from precipitation falling within the immediate watershed. Most of this water enters the Lake by direct runoff through a series of five major streams and their associated lakes, marshland and sub-watersheds. • Lake Minnetonka's ecology makes it easily susceptible to pollution hazards. The combination of a single-source local water supply, relatively small watershed area, many channel restrictions between separate bays, and a single outlet, have resulted in Lake Minnetonka having an extremely long 25-year flush out period for complete water change. The hazard is that once pollutants enter the Lake,they tend to remain for a long time and they are not easily diluted. • Lake Minnetonka has historically suffered from two problems which directly affect its environmental health and its value as a public amenity. One problem which has been worsening with urbanization trends is a deterioration in water quality caused by eutrophication. Eutrophication is the aging process by which natural waters are enriched with nutrients that may stimulate excessive plant growth, including floating algae, attached algae, and rooted weeds. Eutrophication may occur naturally, as sediments accumulate in lake basins over geologic time or it may be induced artificially as a result of human activities,as in Lake Minnetonka. Much of Lake Minnetonka has become more eutrophic during the past century, but sedimentation has been negligible. Instead, the accelerated eutrophication of the Lake, which is due to increased inputs of nutrient elements, particularly phosphorus and nitrogen, is evidenced by the increased growth of algae and weeds. City of Orono Community Management Plan 2020-2040 Part 3A, Page 2