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Soil Suitability and Nitrate Loading Evaluation Page 8 <br /> 25071 South Lammers Road <br /> Tracy, California <br /> June 16, 2023 NATS Job No. 22-355G <br /> in/year (average taken from USDA SCS Soil Survey of San Joaquin <br /> County, Fig 3, page 8, dated October 1992). <br /> Nb = Background nitrate nitrogen concentration of rainfall recharge at the <br /> water table typically falls between 0.5 and 1.0 mg/I (per Hantzsche and <br /> Finnemore; 1992). For this calculation conservatively assumed to be 1.0 <br /> mg/I. <br /> Our nitrate calculation is as follows: <br /> N, _ [I (Nw) (1-D) + R (Nb)] / (I+R) <br /> Nc _ [11.44(40) (1.0-0.25) + 8.4 (1.0)] / (11.44+8.4) = 17.72 mg/I as N <br /> The calculated nitrate of 17.72 mg/I as N is higher than the State drinking water <br /> standard of 10 mg/I for nitrogen (N). <br /> 9.000NCLUSIONS <br /> A suitable soil condition for septic percolation tests in San Joaquin County is defined as a <br /> stratum capable of percolating water between 1 and 60 minutes per inch (min/inch) at a <br /> depth of up to 3.5 feet below existing site grade or 30 min/inch for deeper tests. <br /> Testing performed at the proposed leach field location resulted in a percolation rate of <br /> 30.0 min/inch at a depth of 42 inches. Based on these results, a suitable percolation <br /> rate was observed which is considered adequate for use of a conventional septic <br /> tank/leach trench sewage disposal system. However, as indicated above, nitrate <br /> calculations indicate the potential nitrate-nitrogen (N) concentration in groundwater <br /> resulting from a standard septic system is expected to be 17.72 mg/I as N which is above <br /> the state standard of 10 mg/L. Based on the nitrate-nitrogen (N) concentration an <br /> 4713 ENTERPRISE WAY * SUITE 4* MODESTO * CALIFORNIA * 95356 * 209-545-1108 <br />