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Soil Suitability /Nitrate Loading Study Irerracon <br />Munsch Property ■ Lodi, California <br />January 7, 2022 ■ Terracon Project No. NA217092 <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 residence is 40 mg/L-N. <br />2.3.4.2 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. <br />Based on the results of the shallow and deep soil borings, the proposed leach field is expected to <br />be located within silty sand; therefore, a denitrification estimate of 15 percent was selected. <br />2.3.5 Nitrate Loading Scenario <br />A nitrate loading scenario was performed to determine the impact from the proposed project. The <br />scenario utilizes the variables discussed previously which represent the estimated conditions and <br />uses associated with this project. The following table presents a summary of the nitrate loading <br />calculation for the site. A copy of the nitrate loading calculation is included in Appendix F. <br />Table 10. <br />Summary of Nitrate Mass Balance Equation. <br />" Maximum contaminant level (MGL) for nitrate in drinking water is 10 mg/L-N <br />Based on the nitrate loading balance, nitrate levels for the proposed 3 -bedroom residence is <br />anticipated to increase nitrate levels to 6.6 mg/L-N, below the MCL of 10 mg/L-N. The proposed <br />2 -bedroom second residence is anticipated to increase nitrate levels to 9.7 mg/L-N for the project <br />area, also below the MCL. <br />Responsive ■ Resourceful ■ Reliable 16 <br />Effluent <br />Average <br />Leachfield <br />Net Rainfall <br />Proposed <br />Result (Nc)* <br />Acres <br />Concentration <br />Daily Flow <br />Denitrification <br />Recharge <br />Development <br />(mg/L-N) <br />(A) <br />(Nw) <br />(Q) (gpd) <br />(mg/L-N) <br />(d) <br />(in/year) (R) <br />Proposed 3- <br />bedroom residence <br />6.6 <br />1.47 <br />200 <br />40 <br />15% <br />8.90 <br />Proposed 3 - <br />bedroom residence <br />and 2 -bedroom <br />9.7 <br />1.47 <br />350 <br />40 <br />15% <br />8.90 <br />residence <br />" Maximum contaminant level (MGL) for nitrate in drinking water is 10 mg/L-N <br />Based on the nitrate loading balance, nitrate levels for the proposed 3 -bedroom residence is <br />anticipated to increase nitrate levels to 6.6 mg/L-N, below the MCL of 10 mg/L-N. The proposed <br />2 -bedroom second residence is anticipated to increase nitrate levels to 9.7 mg/L-N for the project <br />area, also below the MCL. <br />Responsive ■ Resourceful ■ Reliable 16 <br />