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DBCP is a nematocide and soil fumigant for vegetables and grapes. It is known to cause male reproductive effects and is classified as a probable human carcinogen. Most domestic use of DBCP was discontinued in 1977 through 1979. The US EPA set the MCL at 0.2 parts per billion (ppb, equivalent to µg/L) because it believes that given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water. The Maximum Contaminant Level Goal (MCLG) for DBCP is zero. Soil Profile and Geologic Information The Site is depicted on the Preliminary geologic map showing Quaternary deposits of the Lodi Quadrangle, California (Marchand and Atwater, 1979). The Site is depicted within a map unit of the Modesto formation lower member described as "Qm, (arkosic alluvium forming Mokelumne River alluvial fan) and Qmjb deposits (basin alluvium derived from Mokelumne and Calaveras Rivers; includes arkosic alluvium, probably glacial outwash, and locally-derived materials; chiefly fine sand and silt) overlain by 0.5 to 1.5 m of Qm2fb deposits (foothill-derived basin and interdistributary overbank alluvium; chiefly clay and silt) (Plate 9). The surface and near surface soils located at the Site are reported by the USDA Web Soil Survey to be composed of Jacktone clay (Plate 10) (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 Reaction ability absorption Symbol (in) Classification mmhos/cm pH (in/hr) fields Jacktone 0-22 Clay; CL, CH <2 6.6-8.4 0.06-0.2 Severe: clay, 0-2% 22-34 Clay loam, clay, silty <2 7.9-9.0 0.06-0.2 cemented slopes, clay; CL, CH pan, peres 180 34-37 Indurated --- --- --- slowly 37-46 Loam, clay loam; CL- <2 7.9-9.0 0.2-0.6 ML, CL 46-60 Cemented --- --- --- 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. Percolation Test Advanced GeoEnviron mental of Stockton conducted a shallow percolation test near the proposed septic disposal area of the Site on February 7, 2020. Information prepared by Advanced GeoEnvironmental is included in Appendix 3; test results are presented in Table 2. LOGE 20-63 Page 5