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Soil Suitability / Nitrate Loading Study <br /> Ernst Property ■ Tracy, CA Irerracon <br /> February 21, 2019 revised April 9, 2019 ■ Terracon Project No. NA197000 <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 /> Result Average Effluent Leachfield Deep <br /> Acres Concentration Percolation <br /> Land Use (Nc)" Daily Flow Denitrification <br /> (mglL-N) (A) (Q)(gpd) (Nw) (d) of Rainfall <br /> (mg/L-N) (R)(in) <br /> Existing Residence 20.2 2.07 700 35 30% 1.01 <br /> Proposed Mobile 18.1 2.07 420 35 30% 1.01 <br /> Home <br /> Existing Residence 38.3 <br /> and Proposed Mobile <br /> Home <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. <br /> Responsive■ Resourceful ■ Reliable 15 <br />