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CMP Part 3A. Environmental Protection Plan <br /> Management of storm water runoff is essential for protection of the water <br /> quality of Lake Minnetonka, for preservation of the natural wildlife habitat <br /> of the marshlands, and for protection against flooding and flood damage. <br /> The discussions above about Lake Minnetonka's water source, about wetlands <br /> function, shoreline protection and flood prevention all have a common <br /> connection to storm water management. The following sections are excerpts and <br /> highlights of the pertinent studies referenced above: <br /> The Metropolitan Council's 208 Water Quality Management Plan (1979) <br /> explained storm water pollution potential as follows: <br /> "Back r� <br /> The problem of urban storm water runoff and the variable pollutants it carries <br /> has received an increasing amount of national attention in the past five years, <br /> largely because the contribution of unrecorded sources to water degradation had <br /> previously not been assessed. Literally hundreds of millions of dollars of <br /> pollution abatement funds are at stake,requiring careful allocation decisions. <br /> The primary water quality problems occurring as a result of urban runoff are <br /> caused by accumulation of pollutants and/or by short, intense 'shock loads' that <br /> result in immediate water quality effects. National studies are showing <br /> repeatedly that urban nonpoint inputs are a significant part of total water <br /> pollution loading. They contribute a load of pollutants equivalent or greater in <br /> some parameters than those released annually by municipal and industrial point <br /> dischargers (this has been locally confirmed by the "Harza Study" as being <br /> particularly relevant to Lake Minnetonka). <br /> Urban Stormwater Pollutants and Pollution Process <br /> The primary pollutants moved by urban stormwater are sediment, oxygen- <br /> demanding substances, nutrients, heavy metals, bacteria, chlorides from road <br /> salt, oil and grease, pesticides and poisonous compounds called polychlarinated <br /> biphenyls(PCB's). <br /> Sedimeut fram urban runoff inerits primary attention both as a pollutant itself, <br /> and because of the tendency of some metals, nutrients and pesticides to adsorb <br /> onto fine soil or organic particles under certain conditions. Urban stormwater <br /> quality has sediment concentrations generally far greater than those of raw <br /> sewage, with predominant sources of sediment being erosion, atmospheric <br /> fallout and vehicular deposition. The detrimental effects of sediment include <br /> decreased light penetration, settling on lake or stream bottoms, transport of <br /> adhered pollutants, clogging of fish gills and decreased aesthetics. In general, <br /> urbanization will increase sediment loads, with areas of rapid development <br /> contributing the largest loads, but with fully developed areas also contributing <br /> large sediment volumes. <br /> City of Orono Community Management Plan 2008-2030 Page 3A-17 <br />