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Nitrate Loading Study Irerracon <br /> Arellano Property Stockton, California <br /> April 26, 2019 a Terracon Project No. NA187058 <br /> The average total nitrogen concentration of domestic wastewater is normally considered to be 20 <br /> to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated <br /> that commercial use will have higher concentrations of total nitrogen when compared to residential <br /> use. For the purposes of the nitrate loading estimate, it is estimated that the average <br /> concentration for total nitrogen in wastewater for the project is approximately 35 mg/L-N over the <br /> long term. <br /> 3.5.1 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the atmosphere. <br /> Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 <br /> percent. Soils with higher clay content, moist soil conditions, high pH, and organic material <br /> denitrify by about 35 percent, and soils with high sand content and fast percolation rates are <br /> estimated to denitrify at a lower rate, about 10 to 15 percent. Based on the silty clay loam soils <br /> anticipated on the site (Section 1.t), hardpan layer, and stratified clay soils to depths of 244 feet <br /> bgs, a denitrification factor of 35 percent was selected. <br /> 3.5.2 Nitrate Loading <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 Average Effluent Leachfield Deep <br /> Land Use (Nc)* Acres (A) Daily Flow Concentration Denitrification Percolation <br /> (mg/L- (Q) (gpd) (Nw) (d) of Rainfall <br /> N) (mg/L-N) (R) (in) <br /> Existing 12.2 2.0 420 35 35% 2.64 <br /> residential use <br /> Proposed 12.2 2.0 420 35 35% 2.64 <br /> residential use <br /> Existing <br /> Residence + <br /> Proposed 24.4 <br /> Residence <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 three <br /> bedroom residence (12.2 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 /> Responsive a Resourceful s Reliable 8 <br />