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Expected On -Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the current and any future residents of the Site. Septic system design should be based on the San Joaquin County On -Site Wastewater Treatment Systems Standards (2017) 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 2021 were the most recent available from this source. According to an analysis of these maps (Plates 6 and 7), ground water elevation near the Site is approximately 10 feet above mean sea level. Ground water flows to the north in the general area at a rate of approximately 2.0 to 2.5 feet per mile. Given that the ground elevation of the Site is approximately 50 feet above mean sea level, the depth to water beneath the Site is estimated to be approximately 40 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. As discussed in the Surface & Subsurface Contamination Report (Live Oak, 2022), approximately 6,000 gallons of diesel fuel spilled on the Site in 2015 due to an aboveground storage tank failure. The spill was cleaned up under Central Valley Regional Water Quality Control Board oversight and received a "no further action" designation. Two common ground -water contaminants in San Joaquin County are nitrate and dibromochloropropane (DBCP). Live Oak reviewed the San Joaquin County Environmental Health Department's maps of Nitrate — Land Use Data and DBCP — Land Use Data dated February 20, 2019 (Plates 8 and 9). According to the nitrate map, three wells within a one -mile radius of the subject Site have been tested for nitrate. Nitrate was detected at concentrations over 10 mg/L-N in all three wells. According to the DBCP map, five wells within a one -mile radius of the Site have been tested for DBCP. LOGE 2233 Page 3