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storm water runoff quantities and speed. Therefore, Orono will preserve its wetlands <br />as much as possible to alleviate downstream flooding. <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 of <br />the marshlands, and for protection against flooding and flood damage. The <br />discussions above about Lake Minnetonka's water source, about wetlands function, <br />shoreline protection and flood prevention all have a common connection to storm <br />water management. The following sections are excerpts and highlights of the <br />pertinent studies refereneed above: <br />The Metropolitan Council's 208 Water Qualitv' Management Plan <br />(1979) explained storm water pollution potential as follows: <br />''Background <br />The problem of urban storm water runoff and the variable pollutants it <br />carries has received an increasing amount of national attention in the past <br />five years, largely because the contribution of unrecorded sources to water <br />degradation had previously not been assessed. Literally hundreds of millions <br />of dollars of pollution abatement funds are at stake, requiring careful <br />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' <br />that result in immediate water quality effects. National studies are showing <br />repeatedly that urb^n nonpoint inputs are a significant part of total water <br />pollution loading. They contribute a load of pollutants equivalent or greater <br />in some parameters than those released annually by municipal and industrial <br />point dischargers (this has been locally confirmed by the "Harza Study" as <br />being particularly relevant to Lake Minnetonka). <br />Urban Stormwater Pollutants and Pollution Process <br />The primaiy' pollutants moved by urban stomnvater are sediment, oxygen ­ <br />demanding substances, nutrients, heavy metals, bacteria, chlorides from road <br />salt, oil and grease, pesticides and poisonous compounds called polychlor ­ <br />inated biphenyls (PCB's). <br />Sediment from urban runoff merits primaiy attention both as a pollutant <br />itself, and because of the tendency of some metals, nutrients and pesticides <br />to adsorb onto fine soil or organic particles under certain conditions. Urban <br />stormwater quality has sediment concentrations generally far greater <br />CMP3A- 13 <br />I <br />I <br />I <br />I I <br />I t <br />I t <br />f 1 <br />t I <br />• I <br />t < <br />» < <br />* % <br />I