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formation upper unit (Plate 9). The Riverbank formation is described as "arkosic alluvium, sand ... and silt, forming terraces, and alluvial fans along the Cosumnes and Mokelumne Rivers." The surface and near surface soils located at the Site are reported by the USDA Web Soil Survey to be composed of San Joaquin loam (Plate 10) (USDA, 2022). The table below presents some selected properties of this soil: Table 1. Selected Properties of On-Site Soils (USDA, 1992) Soil Name and Depth Unified Soil Salinity Soil Perme Septic tank Map Symbol (in) Classification mmhos/cm Reaction -ability absorption pH (in/hr) fields San Joaquin loam, 0-16 Loam; CL-ML, ML <2 5.6-6.5 0.6-2.0 Severe: 0-2% slopes, 16-26 Clay loam, clay; CL <2 6.1-7.8 <0.06 cemented pan, 238 26-60 Indurated --- --- --- peres slowly Note: The table descriptions do not necessarily reflect site-specific soil properties. See description of the map unit for composition and behavior characteristics of the map unit. Soil Borings On October 19, 2022, Live Oak excavated a shallow soil boring near the proposed septic disposal areas for the new houses on the Site. The boring was 4 inches in diameter, 2.13 feet deep, and was excavated by hand auger (Table 2). The location of the boring is indicated on Plate 11. The soil in the boring was similar to that described by the Soil Survey. Sandy silt was encountered to a depth of 6 inches, followed by silty clay with very fine sand to the full depth of the hole. The soil log is presented on Plate 12. Discussion of Soil Lithology Based on the soil observed in the boring, there appears to be limited potential for percolation in the shallow soil zone. Sandy soils generally have a much greater potential for percolation than fine-grained or cemented soils. However, a percolation test is the only accepted method for determining the suitability of the soils for a septic disposal area. Percolation test results are discussed in the following section. Percolation Test A shallow percolation test was conducted at the test location. The soil boring discussed above was used for the percolation test hole. Percolation test procedures conformed to San Joaquin County Environmental Health Department policy. LOGE 2245 Page 5