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within a 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-Urban land 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 Depth Unified Soil Salinity Soil Perme- Septic tank and Map (in) Class Reaction ability absorption Symbol Classification mmhos/cm pH (in/hr) fields San Joaquin- 0-16 Loam; CL-ML, ML <2 5.6-6.5 0.6-2.0 Severe: Urban 16-26 Clay loam, clay; CL <2 6.1-7.8 <0.06 cemented Complex, 26-60 Indurated --- --- --- pan, peres 0-2% slopes, slowly 242 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 December 4, 2020, Live Oak drilled a shallow soil boring to a depth of 3.39 feet; the boring was 4 inches in diameter and was drilled by hand auger. Due to the presence of cemented soils, Central Valley Septic Services was retained to drill the deep boring. On December 12, 2020, Live Oak observed the drilling of the deep percolation test boring by Central Valley Septic Services with a Spiradrill LHD 50; the boring was 12 inches in diameter and 17.58 feet deep (Table 2). The location of the borings is indicated on Plate 10. The surface and near-surface soils in the borings were similar to those described by the Soil Survey; the deeper soil was found to be very sandy. Clay was encountered to a depth of 3 feet, followed by silt to 6.5 feet, clay to 8 feet, cemented silty sand to 13 feet, very fine sand with silt (partially cemented) to 16 feet, and fine to medium sand with silt to the full depth of the hole. 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 20-56 Page 5