Laserfiche WebLink
CMP Part 3A. Environmental Protection Plan <br /> seepage of surface water, increased urbanization may be expected to <br /> bring not only greater surface water run-off but a decrease in the natural <br /> recharge of ground water". <br /> This finding lead to the MCWD policy that each municipality prepare a drainage <br /> plan for surface water resulting from urban runoff and that "each community <br /> should identify swamps and marshes to be left in their natural state", thereby <br /> acting as settling ponds and filters and avoiding direct runoff into Lake <br /> Minnetonka. <br /> The "Harza Study", a program for preserving the quality of Lake <br /> Minnetonka, (1971) determined that the limiting nutrient for algal growth in <br /> Lake Minnetonka was phosphorus and that the natural function of marshland and <br /> wetland was to retard surface water flow and remove nutrients, especially the <br /> phosphorus. And, storm water, especially that portion which runs off from urban <br /> lands, is expected to become an ever more important source of phosphorus <br /> pollution. <br /> The Harza Study noted that preserving wetlands will play an important part in <br /> the future handling of storm water. As the watershed continues to increase in <br /> population, the rate of flow following storms will tend to increase. The existing <br /> urbanized areas were found to be approximately 25% impervious while new <br /> urbanization tended to be 35% impervious. This factor plus the general rate of <br /> urbanization was at that time having the effect of increasing the water resources <br /> of Lake Minnetonka by an equivalent of 4.25 inches per year. This accelerated <br /> flow rate was causing pressure for the construction of storm sewers or other <br /> structures to convey the storm water through the low areas and to reduce the <br /> water level increase. But, the construction of storm sewers or paved channels <br /> allows storm water to by-pass marshes, thereby curtailing the benefit to be <br /> derived from them. On the other hand, by anticipating problems of localized <br /> flooding, development can be restrained in those areas, storm sewers can be <br /> avoided and storm water can be allowed to meander naturally through the natural <br /> filtration system of the marshes. <br /> Therefore, the Harza Study recommended that "the present policy of preserving <br /> lakes and marshes from filling be continued. It is further recommended that the <br /> future construction of storm sewers be minimized to those required to alleviate <br /> local problems. Storm runoff from the watershed should be encouraged to flow <br /> over marshes, not through them in conduits or around them. An attempt should <br /> be made to locate those areas adjacent to marshes which may be flooded <br /> intermittently because of increased runoff caused by future developments. These <br /> areas should be reserved from further development just as though they were a <br /> portion of the adjacent marsh". <br /> City of Orono Community Management Plan 2008-2030 Page 3A-20 <br />