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D. 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. Lines of Equal Depth to Groundwater Maps for the year 2001 illustrate the depth to groundwater at approximately 15 ft. In 2017, the measured depth to groundwater has dropped dramatically to approximately 60 ft. The 2017 Lines of Equal Elevation indicate the groundwater directional flow to be in a north, northeasterly direction. The perc rate obtained requires a minimum soil depth from the bottom of the leachline trenches to the water table to be eight feet, pursuant to Table 1. 10.2 of the SJC OWTS Standards. Therefore, sufficient separation distance exists even when the shallowest water table depth is used: 15 ft - 3.5 ft (42 in. max. trench depth) = 11.5 ft. NLS§ 2.2, 3.1, SSS§ 2.1, 4.2. Since surrounding, and particularly upgradient properties have been intensely farmed for several decades, the potential for nitrate contamination in the underlying groundwater can be considered to be significant. The Coastal Range geology, upgradient agricultural production, and onsite and neighboring OWTS, have elevated the nitrate nitrogen concentration of the onsite well. NLS§ 2.3, SSS§ 4.3, 4.4, 4.5. The domestic well on the property was sampled from the hose bibb at the NWC of the barn structure and tested for the EHD required constituents of nitrate and the agrichemical Dibromochloropropane (DBCP), with the results in Appendix D. Test results reveal a nitrate nitrogen concentration of 16.5 ppm; 6.5 ppm over the Maximum Contaminant Level (MCL) of 10 ppm. The DBCP concentration was determined to be 0.0164 pg/L, or one -twelfth (91.8% decrease) from the MCL of 0.2 gg/L. Calculation of Alkalinity Requirement for Nitrification The nitrate -nitrogen loading calculations below 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 the well water supply in addition to the introduction of human 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 45 mg/L would require: 45 mg/L NH4-N x 7.1 mg CaCO3 = 320 mg/L alkalinity. The alkalinity in the domestic well water supply was measured at 301 mg/L. The alkalinity of the wastes is unknown, but the combination of the well water and wastes would most likely contribute sufficient alkalinity to promote nitrification. E. Climatic Data: Rainfall versus Evapotranspiration NLS§ 3.2. Rainfall data for this locale was obtained from the California Irrigation Management Information System (CIMIS) for the Manteca Station #70, the closest station with applicable data. Deep percolation is estimated by quantifying the average monthly rainfall versus the average monthly evapotranspiration. Theoretically, if the rainfall exceeds the evapotranspiration, the potential for deep percolation may occur. The following Table summarizes the months for the available years (2014, 2015, 2016, and 2017) where potential deep percolation could occur. n Chesney Consulting