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Soil Suitability/ Nitrate Loading Study 1rerracon <br /> Whitlow Property _ Stockton, CA <br /> November 20, 2019 Terracon Project No. NA197078 <br /> The Hantzsche and Finnemore approach is "...a conservative (worst case)first approximation of <br /> groundwater 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- <br /> term effect(i.e., over years)on groundwater 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 in Appendix F. The units <br /> of nitrate used in the mass balance equation are nitrate-N, whose maximum drinking water <br /> contaminant level (MCL) is 10 mg/L. <br /> 2.1 Chemical and Physical Properties of Soil <br /> 2.1.1 Chemical and Physical Soil Properties <br /> Terracon reviewed the USDA NRCS Web Soil Survey and USDA Soil Survey of San Joaquin <br /> County (1992) for information regarding Hollenbeck silty clay soils (Section 1.5). Selected <br /> physical and chemical properties for the soil types are listed in the following table. <br /> Table 8. <br /> Physical and Chemical Properties* <br /> Soil Name/ Depth USDA Unified Soil Clay Permeability Soil Salinity Septic tank <br /> Map o reaction absorption <br /> Symbol (in) Texture Classification (/o) (in/hour) (pH) (mmhos/cm) fields <br /> 0-10 Silty clay CH,CL 600 0.14-0.16 6.6-8.4 <2 <br /> Hollenbeck 10-37 Clay,silty CH,CL 40- 0.14-0.16 6.6-8.4 <2 <br /> silty clay clay 60 severe <br /> 173 Silty clay 30 0.17-0.20 6.6-8.4 <2 slowly <br /> 37-42 loam,clay CL 40 <br /> loam <br /> 42-60 cemented - <br /> 'Selected USDA physical and chemical properties <br /> 2.1.2 Mass Transport Soil Properties <br /> The longer the effluent remains near the surface, the more treatment is enhanced due to natural <br /> processes within the soil. Based on the relatively slow percolation rates and stiffness of the soils <br /> at depth (25 feet bgs), effluent is anticipated to remain within the soil column. <br /> Responsive ■ Resourceful ■ Reliable 14 <br />