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L LJune 23,2006 NOA Project Number: E06058B r 4.0 GROUND WATER INFORMATION L ✓4.1 Ground Water Depth and Gradient LThe 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. L 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 110 and 130 feet below ground surface and flows at a gradient of about 10 feet per mile to the north in the vicinity of the Site. No ground water was encountered by the staff of Neil O.Anderson&Associates, Inc. during the drilling of percolation test holes to a depth of approximately nine feet on June 1,2006. L ✓4.2 Potential Ground Water Contamination Issues Identifying potential ground-water contamination sources was not part of the scope of work for the L soil suitability study. Potential ground-water contamination can occur from a number of sources which often include leaky underground storage tanks,agricultural activities,dairies, septic systems, I and storm water infiltration. Agricultural activities and the use of septic systems in the area should L be considered potential ground-water contamination sources. L ✓4.3 Water Sample Location One well exists on the site. One well permit was found during file review at EHD on March 16, L 2006. A water sample was taken from the spigot of the well head of the well by Ms. Nancy Rosulek of our office on June 2, 2006. L /4.4 Water Sample Constituents ✓ �` The water sample was analyzed for nitrate and DBC ate was found at �6.8-mg/i- 9� `low 4 the maximum contaminant level (MCL) set by the US EPA o was not L detected in the water sample. The analytical reports prepared by FGL Environmen b found in the appendix of this report. L 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 accumulates in the shallow ground water zones. In the early 1900s,natural levels of nitrate in ground water were measured in forty-three (43)wells L throughout the Sacramento Valley by Bryan (1923). 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' Lconditions,ground water concentration containing nitrate is no more then about 13.5 mg/L-NO3 (3 5 L '4A L