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January 7,2003 <br /> Job Number: LG02-026 <br /> Page 4 <br /> "natural" conditions, ground water concentration containing nitrate is no more then about 13.5 <br /> NO3 (3 mg/L-N). Areas having 24.75 mg/L NO3 (5.5 mg/L-N) or more are those in which nitrate <br /> concentrations may be increasing.3 <br /> DBCP was not detected in the water sample. DBCP is a nematocide and soil fumigant for <br /> vegetables, and grapes. It is thought to cause health problems consisting of kidney damage, liver <br /> damage, and cancer. The use of DBCP was discontinued in 1979. The Environmental Protection <br /> Agency(EPA) set the maximum contaminate limit(MCL) at 0.2 parts per billion(ppb)because <br /> the EPA believes that given present technology and resources, this is the lowest level to which <br /> water systems can reasonably be required to remove this contaminate should it occur in drinking <br /> water.4 <br /> 4.0 GEOLOGY, SOILS,AND PERCOLATION TESTS <br /> The surficial geology of the site is alluvial fan deposits derived from the Coast Ranges. These <br /> formation consist of fairly compact mixtures of gravel, sand, silt and clay which often form <br /> heterogeneous and discontinuous layering. <br /> The San Joaquin County Soil Survey indicates the surface and near surface soils located on the <br /> site consist of open pits and gravel excavations (Plate 2).5 Soil properties for this unit are not <br /> presented by the San Joaquin Soil Survey probably due to the lack of original top soil in these <br /> areas of excavation. <br /> One shallow(3-ft deep) and one deep (5-ft deep)percolation test was performed in the area <br /> adjacent to the existing filter bed leach field (Plate 1). These two percolation test locations were <br /> separated by about 5 feet of distance. No ground water was encountered in the borings. The soils <br /> encountered in each boring were a brown silty sand with gravel to 4 feet in depth followed by a <br /> fine clean medium brown sand to a total depth of 5 feet. <br /> 3 Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S.Geological <br /> Survey Professional Paper 1401-B. <br /> 4 EPA, 1999,Drinking water and health,National Primary Drinking Water Regulations,consumer fact <br /> sheet on:DIBROMOCHLOROPRPOANE. Internet:http://www.epa.gov./OGWDW/dwh/c-soc/dibromoc.html <br /> 5 USDA Soil Conservation Service, 1992,Soil Survey of San Joaquin County,California, Sheet 7. <br /> ?pE RSO <br /> D ++ <br /> Z ' <br /> O � <br /> 9S5OC♦ <br /> P <br />