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Expected On-Site Maximum Septic Tank Usage Maximum expected se-"c usage on the Site would be from the existing and any future residential uses' No co struction is planned at this time. Septic system design should be based on t e O ite 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 spring and fall of 2011 were the most recent available from this source. According to an analysis of these maps (Plates 5 and 6), ground water elevation ranges from approximately 50 to 53 feet above mean sea level, ground water flows down to the north at a rate of approximately seven to eight feet per mile in the vicinity of the Site. Given that the ground elevation of the Site is approximately 75 to 90 feet, based on the County ground water maps the depth to ground water below the Site is estimated to range between 22 to 40 feet, depending on the season and location on the Site. 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. Known ground-water contamination exists in the area as a result of activities at the Tracy Defense Depot, Olin Chlor Alkali facility, and former Chevron Lyoth Loading Station. The Surface & Subsurface Contamination Report (Live Oak, 2013) identified evidence that ground water in the vicinity of the Site may contain elevated levels of sodium, chloride, iron, and total dissolved solids. 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). Five nearby wells were identified at addresses located within approximately one-quarter mile of the Site. Four of the wells had been tested for DBCP; it was not detected in any of the wells. Four of the wells had been tested for nitrate as NO3; it was detected in all four wells at concentrations of 26 to 38 parts per million (ppm). The Maximum Contaminant Level (MCL) set by the US EPA for nitrate as NO3 is 45 ppm. LOGE 1304 Page 3