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` October 24,2001 <br /> Job Number:LGOI-320 <br /> Page 5 <br /> ` DBCP was used as a nematocide and soil fumigant for vegetables, and grapes. It is <br /> thought to cause health problems consisting of kidney damage, liver damage, and cancer. The <br /> use of DBCP was discontinued in 1979. <br /> VI. GEOLOGY,SOILS,AND PERCOLATION TEST <br /> The surficial geology of the site is reported to be the Pleistocene age(10,000 years old to <br /> about 1.8 million years old)Modesto Formation. The Modesto Formation is divided into two <br /> members, the lower and upper members. The upper member is present on the site. The upper <br /> member consists of unconsolidated, slightly weathered gravel, sand, silt, and clay.' The Modesto <br /> Formation is generally comprised of old alluvium that forms distinct alluvial terraces, some <br /> alluvial fans, and channel ridges.' (Plate 6). <br /> The soil located on the site is reported to be the Jacktone clay(Plate 7). A selected <br /> excerpt from the Soil Survey of San Joaquin County describes the Jacktone clay as "...somewhat <br /> poorly drained soil. ...typically, the surface layer is very dark gray and dark gray clay about 22 <br /> inches thick The upper 12 inches of the subsoil is dark gray clay and light gray clay loam. The <br /> next 3 inches is a light gray, strongly cemented to indurated hardpan. The next 9 inches is <br /> yellowish brown loam. The lower part to a depth of 60 inches is a yellowish brown, weakly <br /> cemented hardpan. In some areas the surface layer is silty clay or silty clay loam. <br /> ...permeability is slow in the Jacktone soil."6 Table 3 presents an excerpt of some selected <br /> engineering properties for soils located on the subject property. <br /> Helley,E.J.,and Harwood,D.S., 1985. Geologic map of the Cenozoic Deposits of the Sacramento <br /> ` Valley and Sierran Foothills,California. U.S.Geologic Survey Miscellaneous Field Studies Map,MF-1790. <br /> 'Wagner,D.L.and others, 1987. Geologic Map of the Sacramento Quadrangle. California Division of <br /> Mines and Geology Regional Geologic Map Series,Map No. IA. Scale 1:250,000. <br /> 6 USDA Soil Conservation Service, 1992,Soil Survey of San Joaquin County,California, Sheet 12. <br /> p[R50 <br /> 1 <br /> �r <br /> 2 <br /> 0 <br /> Ya <br />