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Soil Suitability and Nitrate Loading Evaluation Page 7 <br /> 25071 South Lammers Road <br /> Tracy, California <br /> June 16, 2023 NATS Job No. 22-355G <br /> 8.0 NITRATE LOADING CALCULATIONS <br /> Per San Joaquin County Environmental Health Department (SJEHD) requirements, the <br /> following summarizes our nitrate loading calculations for the proposed leach field. The <br /> state drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/I as <br /> Nitrogen (N) in groundwater. Presented below is our evaluation of nitrate loading which <br /> uses the Hantzshe mass balance equation (source: Predicting Groundwater Nitrate- <br /> Nitrogen Impacts, Hantzsche, and Finnemore; 1992). <br /> Nc = Calculation of nitrate-nitrogen in groundwater resulting from leach field <br /> source and precipitation (mg/l, as N). <br /> Nc _ [I(NW)(1-D)+R(Nb)1/(I+R) <br /> Where <br /> = Volume rate (Gal/day) of waste water entering the soil from 8 people in <br /> the proposed 8-bedroom single family dwelling. Flow rate 150 gal/day <br /> per bedroom estimated based on US EPA Onsite Wastewater Treatment <br /> Systems Manual--Section 3.5.4 (EPA/625/R-00/008, Feb 2002). <br /> = 8 x 150 gal/day= 1200 gal/day. <br /> Volume rate (1) converted to inches/year and averaged over the gross developed area <br /> (1.41 acre): <br /> = 1200 gal/day x 365 days/year x ft3/7.48 gal x 1 acre/43,560 ftz x 12 in/ft <br /> x 1/1.41 acre = 11.44 inches/year. <br /> NW = Nitrate concentration of nitrified leach-field effluent is assumed to be on <br /> the order of 40 mg/I (average is 35 to 45 mg/I per Hantzsche and <br /> Finnemore; 1992). <br /> D = Fraction of nitrate-nitrogen loss due to dentrification of leach field <br /> effluent is assumed to be 0.25 (most representative of typical onsite <br /> sewage disposal situations per Hantzshe and Finnemore, 1992). <br /> R = Average recharge rate due to rainfall (taken as 80% of annual 10.5 in/yr <br /> with 20% assumed lost to offsite drainage & evapotranspiration) = 8.4 <br /> 4713 ENTERPRISE WAY * SUITE 4 *MODESTO * CALIFORNIA * 95356 * 209-545-1108 <br />