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� Nitrate Loading Study 1rerracon <br /> Arellano Property �:� Stockton, California <br /> April 26, 2019 rr; Terracon Project No. NA187058 <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 B. The units <br /> of nitrate used in the mass balance equation are nitrate as N. The United States Environmental <br /> Protection Agency (EPA) maximum contaminant level (MCL) for nitrate as N in drinking water is <br /> 10 milligrams per liter (mg/L). <br /> 1.0 CHEMICAL AND PHYSICAL SOIL PROPERTIES <br /> 1.1 Chemical and Physical Soil Properties <br /> Terracon reviewed the United States Department of Agriculture (USDA) Natural Resources <br /> Conversation Service (NRCS) Web Soil Survey and USDA Soil Survey of San Joaquin County <br /> (1992) for information regarding soil properties. Based on information obtained from the USDA <br /> sources, site soils consist of Hollenbeck silty clay. Selected physical and chemical properties are <br /> listed in the following table. <br /> Table 1. <br /> Physical and Chemical Properties* <br /> Soil Name Soil Salinity Septic tank <br /> Depth USDA Unified Soil Clay Permeability <br /> /Map (in) Texture Classification (%) (in/hour) reaction (mmhos/ absorption <br /> Symbol (pH) cm) fields <br /> 0-10 Silty clay CH, CL 40-60 0.06-0.2 6.6-8.4 <2 <br /> Hollenbeck 10-37 Clay CH, CL 40-60 0.06-0.2 6.6-8.4 <2 Severe; <br /> -------- --------- ------...--- <br /> ------ <br /> / 173 <br /> ---lty <br /> / 173 37-42 Siloamslowly ay CL 30-40 0.2-0.6 6.6-8.4 <2 perc/s <br /> --- .._.._..__._....__.._..__....__...._.__.........._........_._._._._.........------.. ..-- ---.... - --- --------- <br /> Y <br /> 42-60 Cemented --- --- --- --- <br /> 'Selected USDA physical and chemical properties <br /> 1.2 Mass Transport Soil Properties <br /> The below additional information pertaining to mass transport was obtained from the USDA <br /> sources listed in Section 1.1. <br /> Hollenbeck silty clay soils are located across the site and consist of moderately well drained soils <br /> with 0 to 2 percent slopes. The soils have slow permeability and slow runoff. The rate of water <br /> in-take in irrigated areas is anticipated at 0.1 inches per hour. For homesite development with <br /> septic tank absorption fields, the main limitations are slow permeability, low strength, and shrink <br /> swell potential. Due to the presence of cemented soils "hardpan" and slow permeability, water <br /> may briefly perch above the hardpan. For sites with septic systems, permeability can be improved <br /> by increasing the size of the absorption field, backfilling leach field trenches with sandy material, <br /> and installing long absorption lines. <br /> Responsive w Resourceful w Rc k,'t,0;1 = 3 <br />