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Nitrate Loading Study <br /> Arriaga Property n Stockton, California Irerracon <br /> April 26, 2019 Fj Terracon Project No. NA187059 <br /> 42 inches bgs), hardpan layer, and stratified clay soils to 500 feet bgs, a denitrification factor of <br /> 35 percent was selected. <br /> 3.5.2 Nitrate Loading Scenario <br /> The following table presents a summary of the nitrate loading calculation for the proposed site <br /> use. A copy of the nitrate loading calculation is included in Appendix B. <br /> Table 4. <br /> Summary of Nitrate Mass Balance Equation. <br /> Result Effluent Deep <br /> (Nc)* Average Concentration Leachfield percolation <br /> Land Use Acres (A) Daily Flow Denitrification <br /> (mg/L- (Q)(gpd) (Nw) (d) of Rainfall <br /> N) (mg/L-N) (R) (in) <br /> Existing 12.6 1.25 280 35 35% 2.64 <br /> Residence <br /> Proposed 12.6 1.25 280 35 35% 2.64 <br /> Mobile Home <br /> Existing <br /> Residence + <br /> 25'2 <br /> Proposed <br /> Mobile Home <br /> EPA maximum contaminant level (MCL)for nitrate as N in drinking water is 10 mg/L-N. <br /> Based on the nitrate loading balance calculation (Table 4), nitrate levels for the current two <br /> bedroom residence (12.6 mg/L-N) slightly exceeds the MCL of 10 mg/L-N for nitrate in drinking <br /> water when an average two person occupancy is calculated per bedroom. The construction of <br /> the proposed two bedroom mobile home (12.6 mg/L-N) is anticipated to further increase nitrate <br /> levels to 25.2 mg/L-N, also above allowable limits for groundwater. <br /> 3.5.3 Impact of Nitrate Loading to Nearby Water Sources <br /> Based on a review of the USGS Stockton East (1987) California Quadrangle topographic map <br /> (Appendix A), the site is located at approximately 50 to 55 feet above mean sea level with a <br /> topographic gradient toward the west. The nearest surface water source to the site appears to <br /> be an unnamed intermittent stream located approximately 1,000 feet west of the site. As the <br /> subject property is relatively flat, we do not foresee percolating effluent affecting the surface water <br /> resources. <br /> Responsive■ Resourceful ■ Reliable 9 <br />