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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Ernst Property Tracy, CA <br /> February 21, 2019 Terracon Project No. NA197000 <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 Soil Septic <br /> Name/ Depth USDA Unified Soil Clay Permeability reaction Salinity tank <br /> Map (in) Texture Classification (%) (in/hour) (pH) (mmhos/cm) absorption <br /> Symbol fields <br /> Capay 0-20 Clay CL 40-60 0.06-0.2 6.6-8.4 <2 Severe: <br /> clay/ 20 -60 silty Ctaclay, CL,CH 40-60 0.06-0.2 6.6-8.4 <2 eres <br /> powly <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. <br /> 2.2.3 Current and Future On-Site Ground Water Uses <br /> There are reportedly no wells used to supply drinking water on the site, as noted in Section 1.4.3. <br /> 2.3 Sources and Impact of Nitrate to Groundwater <br /> 2.3.1 Current Off-Site Sources of Nitrate <br /> Agriculture and septic systems in the area may be the most significant sources of nitrate in <br /> groundwater. Septic tank use in the vicinity is discussed in Section 1.3.4. <br /> Responsive ■ Resourceful ■ Reliable 12 <br />