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Soil Suitability and Nitrate Loading Evaluation CTE Job#25-0710 <br /> Great Pacific Nut—Nut Processing Facility Expansion <br /> 3501 Lehman Road <br /> Tracy, California <br /> August 1, 2019 Page 8 of 10 <br /> R = Average recharge rate due to rainfall (taken as 80%of annual 10.5 in/yr with 20% <br /> assumed lost to offsite drainage & evapotranspiration) <br /> = 8.4 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/1 (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 _ [0.645(40) (1.0-0.25) + 8.4 (1.0)] /(0.645+8. = 07 mg/1 as N <br /> The calculated nitrate (6.48 mg/L as N)'14 groundwater Nitrate-Nitrogen Impacts is below the <br /> State drinking waterstandar-d of 10 mg/L for nitrogen (N). <br /> 8.00ONCLUSIONS <br /> A suitable soil condition for septic percolation tests in San Joaquin County is defined as a stratum <br /> capable of percolating water between I and 60 minutes per inch (min/inch) at a depth of up to 3.5 <br /> feet below existing site grade or 30 min/inch for deeper tests. CTE's percolation test results at the <br /> proposed leach field were 16.0 min/inch at a depth of 38 inches. ' WU01 �I <br /> -� ,t-0 sem. <br /> Groundwater was encountered (4/24/19) at 13 feet below existing groundsurface indicating <br /> groundwater level is expected to be at least 10 feet below 36-inch deep dispersion field. As <br /> discussed above, groundwater at this level may represent a perched condition as it was <br /> considerably shallower than levels indicated in groundwater records for the area between 2011 and <br />