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December 10, 1999 Job Number. 599308 Page 4 One ground-water sample was collected from a residential well, located near the site at 6588 West Ripon Road, on November 23, 1999 for testing. The depth of the residential well is unknown. The ground water sample was submitted to the FGL Environmental Laboratory and tested for the presence of dibromochloropropane(DBCP) and Nitrate(NO3) per San Joaquin County Environmental Health Division requirements. A copy of the test results is attached in the appendix. Test results indicate that DBCP was found to be 0.01 ug/1 and nitrate was found at 12.0 mg/I as NO3 (equivalent to 2.7 mg/1 as N). The DBCP detected in the ground water was below the maximum contaminate level of 0.02 ug/l. The nitrate detected in the ground water was reported as NO3 by FGL and is below the maximum drinking water standard of 45 mg/l. This level is equivalent to 2.7 mg/l as N for the maximum drinking water standard of 10 mg/l. The presents 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 originates from agricultural 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 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 of nitrate is no more then about 3 mg/1-N. Areas having 5.5 mg/l-N or more are those in which nitrate concentrations may be increasing. 2 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. VI. GEOLOGY, SOILS,AND PERCOLATION TEST The geology of the site and surrounding area is reported to be the lower member of the Pleistocene age Modesto Formation consisting of unconsolidated and unweathered gravel, sand, ' Bryan,K., 1923,Geology and ground-water resources of Sacramento Valle` of California: U.S. Geological Survey Water-Supply Paper 495,285p. 2 Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S. Geological Survey Professional Paper 1401-B. penes ti o � ass o c•