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Soil Suitability&Nitrate Loading Evaluation CTE Job #25-1084G <br /> New Septic Leech Lines <br /> 21850 East Liberty Rd <br /> Clements, California <br /> January 30, 2021 Paize <br /> D = Fraction of nitrate-nitrogen loss due to denitrification of leach field effluent is <br /> assumed to be 0.25 (most representative of typical onsite sewage <br /> disposal situations per Hantzshe and Finnemore, 1992 &U.S. EPA, 1980, <br /> 1981). <br /> R = Average recharge rate due to rainfall (taken as 80% of annual 17 in/yr with 20% <br /> assumed lost to offsite drainage & evapotranspiration) <br /> 13.6 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/l (per Hantzsche and <br /> Finnemore; 1992) and is assumed to be 1.0 mg/1. <br /> The nitrate loading calculation is as follows: <br /> NC _ [I (NW) (1-D) +R(Nb)] /(I+R) <br /> Nc _ [0.816(40) (1.0-0.25) + 13.6 (1.0)] /(0.816+13.6) = 2.64 mg/l as N <br /> The calculated nitrate (2.64 mg/L as N) for groundwater Nitrate-Nitrogen Impacts is below the <br /> State drinking water standard of 10 mg/L for nitrogen (N). <br /> 10.0 CONCLUSIONS <br /> A suitable percolation rate for conventional onsite waste water treatment system in San Joaquin <br /> County is defined as stratum capable of percolating water between 1 and 60 minutes per inch <br /> (min/inch) at a depth of up to 3.5 feet below existing site grade. CTE's percolation test results at <br /> the proposed leach field was 60 min/inch at a depth of 36 inches and the proposed back up leach <br /> % <br /> T,INC- <br />