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Mass Transport Soil Properties The soil type will allow limited infiltration of water through the surface soils. The longer the effluent remains near the surface, the more biologic treatment may occur. In a situation where permeable soils exist to the depth of the aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. Clayey soils, like those found on the Site, are known to restrict downward movement of water, and may provide nitrate reduction through adhesion to the soil particles. Groundwater Analysis 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 2016 were the most recent available from this source (Plates 6 and 7). According to an analysis of these maps, the ground-water elevation is approximately 39 to 48 feet below mean sea level, depending on the season. The ground-water flow is to the north or west at a rate of approximately 2.5 to 4.5 feet per mile, depending on the season. Given that the ground elevation of the Site is approximately 100 feet above sea level, based on the County ground water maps the depth to ground water below the Site is estimated to range from 139 to 148 feet. San Joaquin County experienced its highest recent ground-water levels in 1983 and 1999. Maps of spring ground-water levels were reviewed for this study (San Joaquin County Flood Control and Water Conservation District, 1983 and 1999); the maps show that depth to water beneath the Site was approximately 107 to 115 feet (Plates 8 and 9). Potential Ground Water Contamination Issues The Nitrate Loading 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 and cattle ranches, 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. LOGE 1918 Page 3