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San Joaquin County Community Environmental Setting,Impacts,and Mitigation Measures <br /> Development Department Geology,Soils,and Seismicity <br /> Soils <br /> The soils in the project area have been mapped by the U.S. Department of <br /> Agriculture, Soil Conservation Service(now called the Natural Resources <br /> Conservation Service),and are described in the Soil Survey of San Joaquin <br /> County, California(McElhiney 1992). The distribution of soils are shown on <br /> Figure 2-8. The Capay general soil map unit covers the project area. It includes <br /> moderately well-drained,fine-textured soils that are very deep and have been <br /> r subject to irrigation. They are soils that formed in alluvium derived from mixed <br /> rock sources(as described in the foregoing section). This general soil map unit <br /> occurs on interfan basins and on alluvial fans,low fan terraces, stream terraces, <br /> and dunes. <br /> Three individual soil map units associated are found at the project area. They <br /> include the Capay clay,0-2% slopes;El Solyo clay loam, 0-2%slopes; and <br /> Zacharias gravelly clay loam, 0-2%slopes. <br /> Table 3.F-1 summarizes soil characteristics for these detailed soil map units. <br /> These soils generally have a slow runoff rate, slow permeability,a slight hazard <br /> of water and wind erosion,and moderate to high shrink-swell potential(i.e., soil <br /> expansiveness). <br /> Table 3.F-1. Soil Characteristics of the Project Area <br /> 6. Land Capa- <br /> Water bility Unit <br /> Soil Map Runoff Erosion Shrink-Swell Imgated( Storie <br /> Unit Horizon Textures Permeability Rate Hazard Potential Nonirrigated Index <br /> ~ Capay clay, 0-20 inches silty Slow Slow Slight High(0-60 IIs/IV 44 <br /> 0-2%slopes clay and clay; inches below <br /> 20-60inches ground <br /> calcareous clay surface) <br /> EI Solyo 0-10 inches clay Slow Slow Slight Moderate(0- IIs/IV 72 <br /> clay loam, loam; 10 inches <br /> ` 0-2%slopes 10-60 inches below ground <br /> calcareous silty surface);high <br /> clay loam (10-60 inches <br /> below ground <br /> .. surface) <br /> Zacharias 0-14 inches Moderately Slow Slight Moderate(0- IIs/IV 66 <br /> gravelly gravelly clay loam, slow 30 inches <br /> �. clay loam, very gravelly clay below ground <br /> 0-2%slopes loam,and clay surface); low <br /> loam; (30-60 inches <br /> 14-30 inches below ground <br /> gravelly clay loam; surface) <br /> 30- 60 inches <br /> Lgravelly loam <br /> Source:McElhiney 1992. <br /> DeSilva Gates Quarry Project <br /> Draft Environmental Impact Report 3.F-3 <br /> J&5 05105.05 <br /> r <br />