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r2 GROUNDWATER INFORMATION NLS§2.1, SSS§4.1. Groundwater depths and elevations throughout San Joaquin County are illustrated on maps published by the County Flood Control and Water Conservation District. The Fall 2016 Lines of Equal Depth Maps and the Lines of Equal Elevation Maps indicate groundwater depth and directional flow. Depth to groundwater is approximately 30 ft bgs and the groundwater directional flow is difficult to determine, but appears to be in a north northeasterly direction. Depth to groundwater maps published in the Spring of 1983 and Spring of 1999 indicate the depth to groundwater is approximately 10 to 15 ft bgs. This may be considered the shallowest depth to groundwater. NLS§2.2,3.1, SSS§ 4.2. Surrounding agricultural properties are currently farmed and have been for decades. Therefore,the potential for nitrate contamination of the underlying groundwater can be considered high, particularly given the fact that the groundwater is not deep (>90 ft)and the regional soil has a high percentage of sand. NLS§2.3, SSS§4.3,4.4,4.5. The domestic well on the property was sampled with the analytical test results and associated documents found in Appendix D. TABLE 3 WATER WELL NITRATE NITROGEN and DBCP TEST RESULTS ANALYTE CONCENTRATION FOUND MAXIMUM CONTAMINANT LEVEL (MCL) Nitrate 15.7 ppm NO;N 10 ppm NO;N(45 ppm NO,) (Nitrate as Nitrogen) DBCP/EDB ND 0.2/0.05 ug/L (Non-Detect) Alkalinity 200 ppm N/A Discussion on the Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations are contingent upon the environmental factors required for nitrification to occur. These conditions include soil pore-space oxygen content, soil temperature,pH, electrical conductivity, organic matter, cation exchange capacity, and alkalinity. Alkalinity in wastewater effluent is derived from well water, in addition to the introduction of wastes. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia- nitrogen(NH4 N)oxidized. Nitrification of the average Total Nitrogen(TN) concentration of 36 mg/L, as determined below, would require: 36 mg/L NH4-N x 7.1 mg CaCO3=256 mg/L alkalinity. The alkalinity in sampled well water was determined to be 200 ppm. Therefore, soil alkalinity and alkalinity from wastes must provide additional alkalinity concentration for nitrification to occur. Page-4- Chesney a e-4- Chesney Consulting