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MOUNTA N HOUSE PROPOSED ALTAMONT HEIGHTS TENTATIVE MAP 4. ENVIRONMENTAL CHECKLIST i 4.6 GEOLOGY AND SOILS o1'50.5 feet, and the soils encountered were very stiff to hard sandy and silty clays to a depth of23 feet. Below that, the soils were dense clayey or sandy silt. Boring B-2, located in the southwest corner of the site, was drilled to a depth of 20.8 feet. The soils encountered were hard, sandy or silty clay to a depth of 4 feet; silty and clayey sand from 4 to 10 feet, and hard, sandy and silty clay below 10 feet. Groundwater was encountered only in Boring B-5 at a depth of 46.5 feet. Groundwater elevations and soil moisture conditions within the project area will vary depending on seasonal rainfall (Kleinfelder USA,2006). SIGNIFICANT IMPACTS IDENTIFIED IN 2005 SPIIIEIR Six potential impacts were identified in the Initial Study for the 2005 SPIIIEIR(EDAW, 2005). There were no'impacts associated with surface rupture along an earthquake fault and use of septic tanks. Impacts associated with expansive soils were-less than significant. Impacts associated with liquefaction, landslides,and soil erosion were less than significant with the incorporation of mitigation measures presented in the MEIR along with the regulations and implementation measures of the MHMP that control construction of k improvements at the Mountain House Community. The impacts associated with strong I seismic ground shaking were found to be potentially significant and unavoidable. MITIGATION MEASURES IDENTIFIED IN 2005 SPIIIEIR The Initial Study for the 2005 SPIIIEIR rioted that the significance of potential impact associated with seismic ground shaking would be reduced, but not entirely eliminated,by the following: - _ 1. Preparation of an Earthquake Preparedness Plan that is being implemented by the MHCSD. 2. Regulations governing design and construction of schools and police, fire and emergency services buildings. 3. Uniform Building Code requirements for construction of residential, commercial and industrial buildings. DISCUSSION REGARDING PROPOSED PROJECT a) Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving: i) Rupture of a known earthquake fault,as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault?..Refer to Division of Mines and Geology Special Publication 42. The project site is not located within, nor is it adjacent to, any Fault-Rupture Hazard Zones (formerly Alquist-Prilolo Special Studies Zones) and no faults that displace valley alluvium 4-29