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March 26, 2001 <br /> NOA Environmental Project Number LE00-429 <br /> . Page 6 <br /> westward beneath alluvium and older sediments The western border is underlain <br /> by east-dipping Cretaceous'and Cenozoic'strata that form deeply burred synclinal' <br /> trough, lying beneath the Great Valley along its western side " <br />' General Soil Information <br /> The subject parcel is generally located on soils identified as Jacktone-Urban land complex, <br /> 0 to 2 percent slopes by the US Department of Agriculture(USDA), Soil Conservation Service, Soil <br /> Survey of San Joa um Counly,California(1992) The following is an excerpted description ofthese <br /> soil units by the USDA Soil Conservation Service <br /> "This nearly level soil unit is in basins Elevation 10 to 40 feet. The average annual <br /> precipitation is about 14 inches, the average annual air temperature is about 60 <br /> degrees F, and the average frost-free period is about 270 days <br />' This unit is 50 percent Jacktone clay and 35 percent Urban land The components <br /> of this unit occur as areas so intricately intermingled that it was not practical to map <br /> them separately at the scale used. <br /> The Jacktone soil is moderately deep to a hardpan and is somewhat poorly drained <br /> It formed in alluvium derived from mixed rock sources. Mottles in the profile <br /> indicate a somewhat poorly drained soil, however, drainage has been improved by <br /> levees and reclamation projects Typically, the surface layer is very dark gray and <br /> dark gray clay about 22 inches thick The upper 12 inches of the subsoil is dark gray <br /> clay and light gray clay loam The next 3 inches is a light gray, strongly cemented <br /> to indurated hardpan The next 9 inches is yellowish brown loam The lower part <br /> to a depth of 60 inches is a yellowish brown, weakly cemented hardpan. In some <br /> areas the surface layer is silty clay or silty clay loam <br /> ty <br /> Permeabilr is slow in the Jacktone soil Available water capacity is moderate The <br />_ <br /> ' About 65 to 136 million years ago <br /> 2 About D to 65 million years ago <br /> 3 V-shaped <br /> • rdeRs <br /> of <br /> F r <br /> d <br /> ♦j504� <br /> t <br /> 1 <br />