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Soil Suitability / Nitrate Loading Study <br />Ernst Property ■Tracy,CA <br />February 21, 2019 revised April 9, 2019 ■ Terracon Project No.NA197000 <br />Responsive ■Resourceful ■Reliable 15 <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 />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 percent to 15 percent. <br />Based on the results of the shallow soil borings, the proposed new leach field is expected to be <br />located within silty sandy soils with clay below 2.5 feet bgs. Based on the soils encountered <br />during our borings and anticipated percolation rate, a denitrification estimate of 30 percent was <br />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 6. <br />Summary of Nitrate Mass Balance Equation. <br />Land Use <br />Result <br />(Nc)* <br />(mg/L-N) <br />Acres <br />(A) <br />Average <br />Daily Flow <br />(Q) (gpd) <br />Effluent <br />Concentration <br />(Nw) <br />(mg/L-N) <br />Leachfield <br />Denitrification <br />(d) <br />Deep <br />Percolation <br />of Rainfall <br />(R) (in) <br />Existing Residence 20.2 2.07 700 35 30%1.01 <br />Proposed Mobile <br />Home <br />18.1 2.07 420 35 30%1.01 <br />Existing Residence <br />and Proposed Mobile <br />Home <br />38.3 <br />* Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. <br />Based on the nitrate loading balance calculation (Table 6), nitrate levels for the proposed use is <br />anticipated at 38.3 mg/L N above the MCL of 10.0 mg/L-N.