SU0000074 SSNL - Laserfiche WebLink

Home Browse Search

September 30,2002 .Tab Number.LG02-310 Page 4 The presence of nitrates and DBCP are not uncommon in shallow ground-water aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in ground water occurs as a r.,. result of the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow ground-water zones. +•• In the early 1900's, natural levels of nitrate in ground water were measured in forty-three (43) wells throughout the Sacramento Valley by Bryan.' It was thought that ground water at that time was close to a"natural'condition_ Based on the work by Bryan, it is estimated that under 4 natural conditions, ground-water concentration of nitrate is no more then about 13.5 NO3(3 mg/L-N). Areas having 24.75 mg/L NO3 (5.5 mg/L-N) or more are those in which nitrate r.. concentrations may increasing.3 DBCP was not detected in the water sample. DBCP is a nematocide and soil fumigant for vegetables, and grapes. It is thought to cause health problems consisting of kidney damage, liver damage, and cancer. The use of DBCP was discontinued in 1979. The Environmental Protection Agency(EPA) set the maximum contaminate limit(MCL) at 0.2 parts per billion ,., (ppb) because the EPA believes that given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminate should it occur in drinking water.' V. GEOLOGY, SOIL,AND PERCOLATION TEST �- The surficial geologic deposits near the site are reported to be composed of Pleistocene age(10,000 year to 2 million years ago) Modesto Formation. Foothill-derived alluvial silt, clay, and minor sand forming terraces,upper fans, and following distributaries across lower fans-, abundant volcanic detritus (Honcut, Wyman, Capay soils).' ' Bryan,K., 1923,Geology and ground-water resources of Sacramento Valley of California: U.S. Geological Survey Water-Supply Paper 495,285p. Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S. Geological Survey Professional Paper 1401-B. i- 4 EPA, 1999,Drinking water and health,National Primary Drinking Water Regulations,consumer fact sheet on:DIBROMOCHLOROPRPOANE. Internet:http:l/www.epa.gov./OGWDW/dwh/c-soc/dibromoc.html ►.. 5 Marchand,D.E.and Bartow,J.A., 1979,Geologic Map of the Cenozoic deposits of the Bellota quadrangle,California. Scale 1:62:500. " DE RS H � N x + o - Ir. L..