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MOUNTAIN HOUSE NEIGHBORHOODS KAND L INMAL STUDY 5.ENVIRONMENTAL CHECKLIST <br /> 6. GEOLOGY AND SOILS <br /> i <br /> iv) Landslides? <br /> Neighborhoods K and L are located on flat terrain(less than 1-percent slopes). <br /> The 1994 MEIR indicated that the project site is located outside areas of <br /> southwest San Joaquin County identified as susceptible to landsliding. Evidence <br /> V of slope failures and/or landslides has not been mapped within or immediately <br /> adjacent to Neighborhoods K or L or the greater Mountain House community. <br /> The geotechnical studies completed for Neighborhoods K and L also concluded <br /> that the potential for earthquake-induced landsliding to occur is considered very <br /> low(Engeo, 2007b and 2010).Therefore, no significant landslide impacts are <br /> expected, and no mitigation is necessary. <br /> b) Would the project result in substantial soil erosion or the loss of topsoil? <br /> I Excessive soil erosion is not expected to occur within Neighborhoods K or L <br /> =_ because average slopes at the project site are less than 1 percent. However, <br /> project grading for cuts and fills made for building pads, roadbeds,and surface <br /> drainage would require the stripping of such areas of all vegetation,debris, <br /> organic topsoil, or any existing fill or other unsuitable material or soil. <br /> Project construction would be required to comply with National Pollutant <br /> FJ Discharge Elimination System (NPDES) program requirements.The Phase I <br /> NPDES storm water program, administered by the State Water Resources <br /> Control Board (SWRCB) Division of Water Quality, regulates storm water <br /> discharges from major industrial facilities, large and medium-sized municipal <br /> separate storm sewer systems(those serving more than 100,000 people),and <br /> construction sites that disturb 5 or more acres of land. Under the program, all <br /> land disturbances of 5 acres or more are required to implement Best <br /> Management Practices(BMPs)to prevent soil erosion and the off-site migration <br /> of sediment-laden runoff during construction. The site-specific plan that includes <br /> erosion control BMPs is called the Storm Water Pollution Prevention Plan <br /> (SWPPP). Additionally, Master Plan Policy 6.8.3(b)and the County <br /> Development Title require that adequate efforts be implemented during <br /> construction to control or eliminate soil erosion and sedimentation associated <br /> with construction activities. <br /> Once construction is completed and project topsoil has become stabilized with <br /> hardscape and vegetation, soil erosion in the project area would be greatly <br /> reduced. Additionally, all urban runoff from the project site would flow to online <br /> water quality basins within the Mountain House Creek corridor that would help to <br /> F; remove sediment and soil particles from site runoff. These basins would require <br /> periodic maintenance, including desilting and vegetative clearing to ensure <br /> proper functionality. Sedimentation and soil erosion water quality issues are <br /> P further addressed in Section 5.8, Hydrology and Water Quality,of this Initial <br /> Study. <br /> Soil erosion and sedimentation were also addressed by Policies 4.2.2.P.a and <br /> 4.2.2.P.d (Grading Standards)and Policy 6.8.3.P.b(Soils, Geologic, and Seismic <br /> Hazards)of the Master Plan. No additional mitigation measures are required to <br /> !t <br /> (917M 1) 5-79 <br />