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_ December 12,2006 <br /> NOA Project Number: E06094A <br /> ignores dispersion,lateral flow, and mixingwith ground water up- <br /> gradient$* flow from up gradient areas. These <br /> f - processes would generally contribute to additional reduction of nitrate-nitrogen concentrations in <br /> ground water the extent that the nitrate-nitrogen concentration of ground-water flow from <br /> up-gradient areas <br /> s is lower." <br /> a F1 <br /> The Hantzsche and Fennemore approach is "...a conservative (worst case) first approximation of <br /> - ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage <br /> disposal systems and precipitation. This (the equation and approach) is for estimation of long-term <br /> effect (i.e., over years) on ground-water quality, and is not intended for prediction of seasonal <br /> changes" (Hantzsche and Finnemore, 1992). <br /> The method takes into account the development area, soil denitrification factor,rainfall volume, <br /> rainfall nitrate concentration,waste effluent quantity, and waste effluent nitrate concentration. The <br /> formula, assumptions and calculations used for the analysis are shown on Plates 9 and 10. The units <br /> Of nitrate used in the mass balance equation are nitrate-N,whose maximum drinking water <br /> contaminant level is 10 mg/L. <br /> 1.0 CHEMICAL AND PHYSICAL PROPERTIES OF SOIL <br /> 1.1 Chemical and Physical Soil Properties <br /> The Site is depicted on the Preliminary Geologic Map of the San Francisco - San Jose Cenozoic <br /> �-, Deposits of the Tracy Quadrangle, California (1991),is within a region of Quaternary Fan deposits. <br /> The unit is composed of gravel, sand silt and clay. <br /> The surface and near surface soils located at the Site are reported by the San,Joaquin Gouniy Soil Survey <br /> to be composed of the Scribner clay Ioam, 0-2% slopes. Table 1 <br /> of the soils: presents some selected properties <br /> Table 1. <br />�} San.Joaquin County Soil Survey <br /> Selected Soil Pro erties of On-Site Soils. <br /> EEJ <br /> 0-24 Clay loam;CL <2 6.1 -7.8 0.2-0.6 Severe: <br /> y <br /> 24-60 Stratified loam to silty clay loam; <2 6.6-8.4 0.2-0.6 wetness, <br /> CL <br /> peres slowly <br /> i <br /> 1.2 Mass Transport Soil Properties <br /> The percolation tests have revealed that the soils are fairly permeable. These soils will allow <br /> moderate to rapid infiltration of water through the surface soils. If the permeable soils exist to the <br /> depth of the ground water table,it is possible that surface contaminates may be transported fairly <br /> rapidly. <br /> 3 <br />