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Soil Suitability / Nitrate Loading Study <br />Ernst Property ■Tracy,CA <br />February 21, 2019 revised April 9, 2019 ■ Terracon Project No.NA197000 <br />Responsive ■Resourceful ■Reliable 12 <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 Capay clay soils (Section 1.5). Selected physical and <br />chemical properties for the soil types are listed in the following table. <br />Table 1. <br />Physical and Chemical Properties* <br />Soil <br />Name / <br />Map <br />Symbol <br />Depth <br />(in) <br />USDA <br />Texture <br />Unified Soil <br />Classification <br />Clay <br />(%) <br />Permeability <br />(in/hour) <br />Soil <br />reaction <br />(pH) <br />Salinity <br />(mmhos/cm) <br />Septic <br />tank <br />absorption <br />fields <br />Capay <br />clay / <br />118 <br />0-20 Clay CL 40-60 0.06-0.2 6.6-8.4 <2 Severe: <br />percs <br />slowly20-60 Clay, <br />silty clay CL, CH 40-60 0.06-0.2 6.6-8.4 <2 <br />*Selected USDA physical and chemical properties <br />2.1.2 Mass Transport Soil Properties <br />The percolation test has revealed that site clay soils will allow for slow infiltration at shallow depths <br />between 3.0 feet bgs. The longer the effluent remains near the surface, the more treatment is <br />enhanced due to natural processes within the soil. Based on the slow permeability and high water <br />absorption capacity of the clay soils, effluent is anticipated to remain within the clay soil column <br />much longer when compared to more permeable sands, silts, and loamy soils. <br />2.2 Groundwater Analysis <br />2.2.1 Regional Groundwater <br />A discussion of regional groundwater, including depth to groundwater and flow gradient is <br />included in Section 1.4.1. No significant seasonal trends were evident from the sources <br />consulted. <br />2.2.2 Potential Ground Water Contamination Issues <br />A discussion of issues related to potential groundwater contamination is included in Section 1.4.2.