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Soil Suitability/ Nitrate Loading Study 1rerracon <br /> Souza Property Tracy, CA <br /> February 28, 2020 - Terracon Project No. NA207011 <br /> Table 12. <br /> Summary of Nitrate Mass Balance Equation. <br /> Result Average Effluent Leachfield Net Rainfall <br /> Acres Concentration <br /> Land Use (Nc)` Daily Flow Denitrification Charge(R) <br /> (mg/L-N) (A) (Q)(gpd) ( (mg/L)N) (d) (in/year) <br /> Existing Residence 18.2 1.49 250 45 20% 2.33 <br /> Proposed Residence 16.3 1.49 200 45 20% 2.33 <br /> Total 34.5 <br /> *Maximum contaminant level(MCL)for nitrate in drinking water is 10.0 mg/L-N. <br /> Based on the nitrate loading balance, nitrate levels for the existing residence is 18.2, above the <br /> MCL of 10.0 mg/L-N. The proposed second residence is anticipated to add 16.3 mg/L-N for a <br /> combined total of 34.5 mg/L-N, also above the MCL of 10.0 mg/L-N. <br /> 2.3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Based on the aerial photographs and topographic maps (Section 1.1), no surface water source is <br /> near the site. <br /> 2.4 Discussion of Nitrate Loading Results <br /> 2.4.1 Total Nitrate Impact <br /> Based on the method and assumptions described, the result of the nitrate loading balance (34.5 <br /> mg/L N for both residences) indicates that the development on the parcel may cause a buildup of <br /> nitrates in the aquifer above the MCL of 10.0 mg/L-N. <br /> 2.4.2 Methods of Mitigation <br /> Based on the nitrate loading results, nitrate impacts to groundwater are anticipated; therefore, <br /> mitigation measures may be required for the project. <br /> 3.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The soils encountered on the site generally consisted of silt with sand and lean clay with sand. <br /> Satisfactory percolation rates of 8.33 min/inch (61)at 3.0 feet bgs and 20.83 min/inch (B2)at 10.0 <br /> feet bgs were obtained in the proposed leach field, west of the proposed second residence <br /> location. The existing onsite septic system includes two leach lines connected to two 20 foot long <br /> by 10 foot deep sumps. Septic systems in the vicinity consist of septic tanks and leach lines <br /> connected to sumps and/or filter beds. <br /> Responsive ■ Resourceful ■ Reliable 16 <br />