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November 24, 1999 Job Number.S99272 Page 4 attached in the appendix. Test results indicate that DBCP was not detected(ND) and nitrate was found at 22 mg/1 as NO3 (4.8 mg/1 as N). 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 4.8 mg/1 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/1-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. VL 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, silt, and clay3 (Plate 6). These types of deposits are commonly unconsolidated arkosic sediment, often heterogeneous in nature, and correspond with the Tioga glaciation in the Sierra Nevada. The soils located on the site are reported to be the Veritas fine sandy loam(Plate 7). The Veritas fine sandy loam is described by the Soil Survey report as"moderately well drained, nearly I Bryan,K, 1923,Geology and ground-water resources of Sacramento Valley of California:U.S. Geological Survey Water-Supply Paper 495,285p. 2 Hull,L.C., 1984, Geochemistry of Ground Water in the Sacramento Valle}. California: U.S. Geological Survey Professional Paper 1401-B. 3 RW.Page, 1986,Geology of the Fresh Ground-Water Basin of the Central Valley,California,with Texture Maps and Sections. Unites States Geologic Survey Professional Paper 1401-C. ?pE RSO 1 � Z W O ti r �SSOG\