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• Expected On-Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the existing and future employees of HD Supply. The existing septic system will be expanded to accommodate the increased use. 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 fall of 2014 and spring of 2015 were the most recent available from this source. According to an analysis of these maps (Plates 5 and 6), ground water elevation is approximately 52 to 63 feet below mean sea level; ground water flows toward the northeast at a rate of approximately five to six feet per mile in the vicinity of the Site. Given that the ground elevation of the Site is approximately 41 to 42 feet, the depth to water below the Site is estimated to be 93 to 105 feet, depending on the season. • 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. 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. Four wells were identified within approximately one-half mile of the Site. Nitrate as NO3 was detected in all of the wells at concentrations of 7.4 to 24.4 mg/L. None of the wells had been tested for DBCP. The Maximum Contaminant Level (MCL) set by the US EPA for nitrate as NO3 is 45 mg/L (equivalent to 10 mg/L-N); the MCL for DBCP is 0.2 µg/L. On-Site Wells A domestic well is located north of the existing warehouse on the Site (Plate 3). No well permits were identified for the Site at the San Joaquin County Environmental Health Department. • LOGE 1628 Page 3