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Soil Suitability/Nitrate Loading Study Irerracon <br /> Gribaudo Property ■Acampo, CA <br /> November 12, 2019 ■ Terracon Project No. NA197081 <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 45 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 15 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 sandy silt soils that cemented with depth. Based on the cemented soils <br /> encountered during our borings and depth to groundwater (120+ feet bgs), a denitrification <br /> estimate of 35 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 /> Result Effluent Deep <br /> Average Leachfield <br /> (Nc)' Acres Concentration Percolation <br /> APN Land Use Daily Flow Denitrification <br /> (mg/L- (A) (Q)(gpd) (Nw) (d) of Rainfall <br /> N) (mg/L-N) (R)(in) <br /> Existing 3 <br /> bedroom <br /> 017-260-31 residence 11.9 2.0 420 45 35% 4.49 <br /> Existing and <br /> Proposed <br /> Acreage <br /> Nitrate as N Total <br /> 11.9 <br /> APN 017-260-31 <br /> 017-260-30 Existing 0 35.81 0 45 35% 4.49 <br /> Acreage <br /> Responsive■ Resourceful ■ Reliable 16 <br />