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April 25,2001 Job Number: LGOl-498 Page 5 The test results indicated that DBCP was non-detectable ) 3 D') and nitrate as NO was ' _ found at 79 mg/I (17.6 mg/1-N). The result of the nitrate test indicates the ground water is above me maximum contaminate'level set by the United States Environmental Protection Agency of 45 g/1-NO3 for nitrate(or 10 mg/l as Nitrate N). The presence of nitrates and DBCP are not uncommon.in shallow ground-water aquifers in Sari Joaquin County and.other parts of the Central Valley. Nitrate in groundwater occurs as.a result of the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is . mobile and,often•accumulates'in the shallow groun&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 `.`natural" conditions. Based on the'work by Bryan,.it is estimated that under "natural"conditions, groundwater.concentration containing 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 , concentrations maybe increasing.' ' k Y DBCP was not detected in the water sample. DBCP is a nematocide'and soil fumigant p g 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. arts per billion p (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 4 -occur.in drinking Water. VI. GEOLOGY, SOILS,AND PERCOLATION TEST The siirface geology at the site is shown on Atwater's map and is composed of the Holocene and.(or)upper.Pleistocene age alluvium named as Alluvium of Suprati.dal Flood Plains ?Bryan,K. 1923,Geology and ground-water resources of Sacramento Valley of California:U.S.. , Geological'Survey Water-Supply Paper.495,285p. 3 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://www.epa.gov./OGWDW/dwh/c-soc/`dibromoc.html N 0 r