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TABLE 2 <br />SOIL PROFILE CHARACTERISTICS AND <br />ANALYTICAL TEST RESULTS <br />SAMPLE I.D. DEPTH <br />SOIL TEXTURE <br />SOIL NITRATE- <br />pH AND <br />CLASSIFICATION <br />NITROGEN <br />CATION EXCHANGE CAPACITY <br />(USCS) <br />CONTENT <br />In meq/100g <br />4 P'1' <br />Sandy Clay Loam <br />16 ppm NO3-N <br />7.3 12.3 meq/100g <br />(SM -CL -ML) <br />8 FT <br />Sandy Loam <br />9 ppm NO3-N <br />7.6 13.3 meq/100g <br />(SM -ML) <br />12 FT . <br />Clay, <br />14 ppm NO3-N <br />7.8 20.3 meq/100g <br />(CL) <br />The most important soil characteristic determined was the clay content percentage of 46.3% at the <br />12 ft depth. The thickness of this clay stratum is unknown, but will certainly attenuate downward <br />nitrate migration. This nitrate attenuation -and subsequent denitrification by clay strata has been <br />observed in numerous San Joaquin County projects. <br />The soil nitrate -nitrogen concentration yielded interesting results. It is theorized that excessive <br />NO3-N was denitrifying through the shallow sandy clay loam soil, then percolated quickly through <br />the sandy loam stratum and then increased in concentration again as the nitrate congregated on top <br />of the clay soil stratum. <br />RECALCULATION OF NITRATE -NITROGEN EQUATION <br />Two parameters in the original nitrate loading equation by LiveOak have been changed. First, <br />because a significant 46.3% clay soil was encountered at the 12 ft depth under the effluent disposal <br />area, the denitrification factor can be increased from 35% to 45%. Secondly, the Net Rainfall <br />Recharge (NRR) value of 2.67 in/yr used by LiveOak has also been increased based upon rainfall <br />data used and approved by EHD for another Study, four miles to the southeast (SR0082464/65). <br />This referenced NRR data uses USGS Soil Survey precipitation values, correlated with CIMIS <br />reference evapotranspiration data, and then Et adjusted by a general turf grass lawn plant factor of <br />60%. Using these parameters, a Potential Deep Percolation (PDD).factor of 6.39 in/yr is derived as <br />illustrated below in Table 3: <br />Page -2- <br />Chesney Consulting <br />