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Expected On-Site Maximum Septic Tank Usage Maximum expected septic usage on the Site would be from the existing and any future residential uses. Septic system design should be based on the On-Site Wastewater Disposal Standards (2003) or other engineering recommendations. Ground Water Information Depth and Gradient Live Oak reviewed ground-water elevation information available from the San Joaquin County Flood Control and Water Conservation District to determine the ground water levels near the Site. Data from the fall of 2010 and spring of 2011 were the most recent available from this source. According to an analysis of these maps (Plates 6 and 7), ground water elevation in the vicinity of the Site ranges from zero to 10 feet below mean sea level. Groundwater flows down in a southerly direction; a flow rate could not be calculated because the Site is slightly west of the mapped area. Given that the ground elevation of the Site is approximately 20 feet, based on the County ground water maps the depth to ground water below the Site is estimated to range between 20 to 30 feet. Potential Ground Water Contamination Issues The Soil Suitability Study is not intended to be an investigation into ground-water contamination sources, and no such investigation was conducted. Many sources can contribute to ground water contamination, including leaking underground storage tanks, agricultural activities, dairies, septic systems, and storm water infiltration. Agricultural activities and the use of septic systems in the area are known ground water contamination sources with the potential to impact the Site. The Site once housed a dairy operation; the milk barn is still present. Animal facilities can result in elevated levels of nitrates and other contaminants in soil and ground water. Live Oak reviewed the EHD's Water Well Data Table dated March 10, 2009 for nearby addresses that have been tested for nitrate and dibromochloropropane (DBCP), common ground water contaminants in San Joaquin County. Six nearby wells were identified at addresses located within approximately one-half mile of the Site. Five of the wel+s had been tested for D,_BCP; it was detected in two, at concentrajions of 0.15 and 0.49 parts per billion (ppb). Five of t Is had been tested foreitrate;-it was detected-j"ll five at concentrations of 2. to 93 pa per million (ppm). The Maximum Contaminant Level (MCL) set by the US EP or DBCP is 0.2 ppb; the MCL for nitrate as NO3 is 45 ppm. LOGE 1112 Page 3