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map unit of the Riverbank formation middle unit, described as "arkosic alluvium forming Mokelumne River terraces and alluvial fan; chiefly sand; probably glacial outwash" (Plate 8). The surface and near surface soils located at the Site are reported by the USDA Web Soil Survey to be composed of the San Joaquin complex (Plate 9) (USDA, 2020). The table below presents some selected properties of this soil: Table 1. Selected Properties of On-Site Soils (USDA, 1992) Soil Name and Map Symbol Depth Unified Soil (in) Classification Salinity mmhos/cm Soil Perme- Septic tank Reaction ability absorption pH (in/hr) fields San Joaquin 0-16 Loam; CL-ML, ML <2 5.6-6.5 0.6-2.0 Severe: Complex, 0- 16-26 Clay loam, clay; CL <2 6.1-7.8 <0.06 cemented 1% slopes, 26-60 Indurated pan, percs 241 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 January 14, 2020, Live Oak observed Central Valley Septic Services drill shallow and deep percolation test borings on the Site. The borings were drilled with a Spiradrill LHD 50; they were 12 inches in diameter and 3.49 and 13.17 feet deep (Table 2). The location of the borings is indicated on Plate 10. On January 20, Live Oak cleaned out and deepened the deep test hole by hand auger; the final depth of the hole was 16.40 feet. The soils in the borings were similar to, though sandier than, those described by the Soil Survey; the deeper soil was found to be very sandy. Partially cemented clayey silt with fine sand was encountered to a depth of 4 feet, followed by partially cemented silty sand to a depth of 10 feet feet, followed by silty fine sand to a depth of 12 feet, followed by fine to medium sand with silt to 15.9 feet, followed by sandy clay to a depth of 16.4 feet. The soil log is presented on Plate 11. Discussion of Soil Lithology Based on the soil observed in the borings, there appears to be limited potential for percolation in the shallow soil zone, but good potential for percolation in the deep 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. LOGE 20-59 Page 5