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SECTION 2 <br />Study Area Characteristics <br />Table 2 -7 <br />Runoff Potential in the River Road Santa Clara Basin <br />Location <br />Medium <br />Low <br />Negligible <br />No <br />Data* <br />Total <br />Within UGB <br />80.7% <br />17.3% <br />0.5% <br />1.4% <br />100% <br />Outside UGB <br />75.9% <br />22.5% <br />0.3% <br />1.3% <br />100% <br />Total Basin <br />78.7% <br />19.5% <br />0.4% <br />1.4% <br />100% <br />*Includes borrow pits and water features such as ponds <br />Source: NRCS Soil Data, December 2006. <br />2.8.3 Erodible Soils <br />Highly erodible soils have significant stormwater management implications. If not properly <br />protected during construction and land clearing activities, erosion and sedimentation from these <br />soils can have the following negative effects: <br />• Reduction in the conveyance capacity of downstream stormwater facilities resulting in <br />potential drainage and flooding problems. <br />• Reduction or elimination of aquatic habitat and covering or destroying of spawning beds. <br />• Water quality impacts due to pollutants that are attached to sediments. <br />The Soil Survey ofLane County indicates soils in this basin are generally not susceptible to high <br />levels of erosion (See Map 8). <br />2.8.4 Unstable Slopes <br />Soils that are subject to slumping can present structural problems especially where extensive <br />grading is made for roads and building pads. <br />The Soil Survey ofLane County indicates there are no soils in this basin subject to slumping. <br />2.8.5 Hydric Soils <br />Hydric soil is one of three criteria for determining the presence of wetlands; the other two being <br />inundated or saturated soil conditions and the presence of hydrophytic vegetation. Federal and <br />state regulations limit activities that can occur in wetlands, including the direct discharge of <br />untreated stormwater runoff. The Oregon DEQ has not yet established such standards for <br />discharging into wetlands. <br />The following table displays the percentage of hydric soils found in the basin. Hydric soils areas <br />are located almost entirely west of the Northwest Expressway corresponding to historic low <br />lying drainage areas (See Map 9). <br />0:\25695978 Eugene RR -SC Final Basin P1an\Master P1anTINAL 2- 2010\Master_Plan 3- 11- 10_FINAL_ Word _Version.doc 2-27 <br />