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STORMWA TER <br />INFILTRATION <br />OVERVIEW <br />Published by Rice Creek Watershed District <br />3585 Lexington Avenue North, Suite 330 <br />Arden Hills, Minnesota 55126 -8056 <br />Phone: (651) 766 -4191 Fax: (651) 766 -4196 <br />District Engineer: Montgomery Watson <br />Several cities and townships in the District <br />have identified additional runoff volume from <br />developing areas as a priority problem. This <br />coincides with a national trend to question <br />how we design our communities with respect <br />to stormwater. The RCWD looked at the issue <br />in depth in 1995 and revised their <br />management plan and rules to tackle the <br />problem. This is one of two fact sheets <br />published by the RCWD to outline an initial_ <br />strategy. This document provides an overview <br />of stormwater .controls utilized by local <br />government officials and planners. The second <br />companion document provides additional . <br />technical information for developers and <br />engineers to utilize during design and <br />permitting. <br />INTRODUCTION <br />When buildings, parking lots, and streets are <br />built the area available for rain to infiltrate — <br />soak in — is reduced dramatically. The water <br />that runs off from these hard areas represents <br />water that our community then has to pond <br />somewhere, route into a storm sewer, or send <br />to a ditch. A typical residential development <br />may have only 50% of its total area remaining <br />to soak up rainwater. Commercial and <br />industrial sites commonly leave as little as <br />20%. <br />WASHINGTON <br />COUNTY <br />HENNEPI N <br />COUNTY <br />The large sources of impervious surfaces in a <br />typical developed community . are roads, <br />parking lots, driveways, and roof tops. The <br />following figure shows the relative proportion <br />of these impervious surfaces. <br />Source of Impervious Surfaces <br />35% <br />■ Streets <br />D sidewalks <br />▪ PErldng!DriYeways <br />E Roofs <br />Runoff management in the RCWD is <br />important for flood control and for <br />maintaining and improving the water quality <br />of lakes and streams in this District. Reducing <br />runoff benefits: <br />■ citizens, by reducing flood frequency and <br />duration. <br />• Cities, by minimizing street and storm <br />sewer construction and long-term <br />maintenance costs. <br />