Laserfiche WebLink
May 21,2002 <br /> 6. Job Number:LG02-140 <br /> Page 5 <br /> L nitrate in ground water were measured in 43 wells throughout the Sacramento Valley by Bryan' <br /> It was thought that ground water at that time was close to `natural"conditions. Based on the <br /> work by Bryan, it is estimated that under natural conditions, groundwater concentration of nitrate <br /> is no more than about 3 mg/L-N(that's about 13.5 mg/L as NO3). Areas having 5.5 mg/L-N <br /> (that's about 24.8 mg/L as NO3) or more are those in which nitrate concentrations may be <br /> increasing.' <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 /> 6. VI. GEOLOGY,SOILS, AND PERCOLATION TEST <br /> The surficial geology of the site is reported to be the Pleistocene age(11,000 years to <br /> ` about 2 million years old) Riverbank Formation. This formation is described as weathered <br /> reddish gravel, sand and silt often forming alluvial terraces and fans.' The Riverbank in the San <br /> Joaquin Valley is predominately arkosic alluvium while the Sacramento Valley contains more <br /> 6. mafic igneous rock fragments 6(Plate 6). Essentially,the Riverbank Formation is consolidated <br /> older alluvium. <br /> 6. The surface and near surface soils located on the site are described by Soil Survey of San <br /> Joaquin County. Five(5) soil units were described for the site. Note that soil unit No. 135 has <br /> two individual soils that make up the unit. A summary of selected engineering soil properties are <br /> 3 Bryan,K., 1923,Geology and ground-water resources of Sacramento Valley of California: U.S. <br /> Geological Survey Water-Supply Paper 495,285p. <br /> 4 Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S. Geological <br /> Survey Professional Paper 1401-B. <br /> 5 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. 1A. Scale 1:250,000. <br /> ` 6 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 /> OER O <br /> 4 <br />