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Fi October 31, 2005 NOA Project Number: E05137A 4.0 GROUND WATER INFORMATION j 4.1 Ground Water Depth and Gradient The San Joaquin County Flood Control and Water Conservation District (1998 and 1999) ground water depth and elevation maps were reviewed to determine the ground water levels near the Site. The Fall 1998 and Spring 1999 maps are the most current official maps available from the County. According to these maps (Plates 3-6),ground water lies between 120 and 160 feet below ground surface and flows at a gradient of about twenty to thirty feet per mile to the east in the vicinity of the Site. No ground water was encountered by the staff of Neil O.Anderson&Associates, Inc. during the drilling of six percolation test holes to depths of 3.5 and 25 feet on October 13 and 28, 2005. F14.2 Potential Ground Water Contamination Issues ` ' Potentialground-water contamination can occur from a number of sources which often include leaky underground storage tanks,agricultural activities, dairies, septic systems,and storm water F! infiltration. Agricultural activities and the use of septic systems in the area should be considered potential ground-water contamination sources. 4.3 Well History and Water Sample Location One private well exists on the Site. No well permits were found for the Site during file review at EHD on October 21, 2005. A water sample was taken from a faucet fed by the domestic well on the west side of the residence by Ms. Nancy Rosulek on October 10, 2005. F14.4 Water Sample Constituents Y The water sample was analyzed for nitrate an BC urate s found at 10.4 mg/L-NO3,well below the maximum contaminant level(MCL set by the US EPA of 45 mg/L-NO3. DBCP was Finot detected in the water sample. The analytical reports prepared by Precision Enviro-Tech can be found in the appendix of this report. The presence of nitrates is 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 result of the application of fertilizers,livestock waste, and untreated septic tank waste. Nitrate is mobile and often F1accumulates in the shallow ground water zones. Fi F14