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ENGEO <br /> <br />INCORPORATED <br /> <br />Surface Rupture <br /> <br />Since the western portion of the parcel includes the mapped trace of the Calaveras fault, the risk <br />of ground rupture within this portion of the site is high. An earthquake on the Calaveras fault <br />could cause shearing of the ground surface within the fault setback zone. The resulting ground <br />deformation would likely result in damage to geotechnical mitigation improvements such as <br />subdrains, fences and concrete ditches. <br /> <br />Slope Instability and Landslides <br /> <br />The risk of landslides is not unique to the property, but is present throughout hillside projects in <br />the San Francisco Bay Area. Landslides are a common geologic phenomenon and are part of the <br />process of mass wasting. Weathered or fractured bedrock and soil are transported downslope <br />over geologic time as a result of gravitational, hydrostatic and seismic forces. <br /> <br />Relatively shallow landslides or areas of slope instability were initially mapped during the <br />preliminary geologic studies for the subdivision. During project design, a landslide deposit was <br />identified in the southwestern comer of the site by the geotechnical consultants. A series of <br />subdrains, engineered keyways and benches will be installed during the landslide and slope <br />repairs. When completed, an "as-built" plan will be prepared by the geotechnical consultants <br />which shows the limits of the landslide repair, the subdrain locations and outlets. <br /> <br />Graded cut slopes could result in the destabilization of open-space slopes and cause landslides <br />possibly extending into adjacent developed land. Of lesser, but high impact, risk is the potential <br />failure of eng/neered graded slopes within the residential subdivision which could affect more <br />thart one lot and/or dwelling. <br /> <br />4992.5.001.01 <br />February 28, 2003 6 DRAFT 2 <br /> <br /> <br />