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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 2017 and the spring of 2018 were the most recent available from this source. The Site is just beyond the mapped area (Plates 4 and 5); the closest ground -water contours are zero to ten feet below mean sea level. The ground -water gradient beneath the Site could not be calculated. Given that the ground elevation of the Site is approximately 8 to 9 feet above mean sea level, extrapolation would suggest a depth to water of 8 to 19 feet below ground surface in the area. As part of this investigation, Live Oak excavated a boring to ground water adjacent to the percolation test hole on the Site. First ground water was measured at a depth of 10.33 feet in the boring on July 1, 2021. It is anticipated that water levels beneath the Site will fluctuate, especially on a seasonal basis, depending on rainfall, irrigation, and pumping practices in the area. 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. 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 6 and 7). According to the nitrate map, two wells within a one -mile radius of the subject Site have been tested for nitrate. One of these wells was found to contain nitrate at a concentration between 0.1 and 5.0 mg/L-N; no nitrate was detected in the other well. According to the DBCP map, one well within a one -mile radius of the Site has been tested for DBCP; no DBCP was detected. The Site is located approximately 450 feet northeast of a listed contaminated site, the "Thornton drainage project," in which petroleum -contaminated soil was encountered during trenching activities for a storm drain project in 1997. Based on a review of documents available on the GeoTracker website (California State Water Resources LOGE 2135 Page 3