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Geological Teckrricsl� City of Escalon Project No.: 750.2 Page 10 May 16,2005 F. Background wells show similar pH, EC, ORP, DO and temperature readings to those recorded in wells near the contaminated zone. The source of contamination has been removed and it is likely the site will return to background conditions via natural attenuation. G. According to the USDA Soil Survey of San Joaquin County, California (McElhiney, M. A., 1992); the soils below the site are very deep, somewhat excessively drained, nearly level soil on dunes with 0 to 2 percent slopes. The potential for health risks caused by human exposure (dermal, ingestion or inhalation) is negligible due to unlikely contact with subsurface hydrogeology. H. The potential for damage to wildlife, crops, vegetation and physical structures caused by exposure to contaminants is minimal due to the reasons discussed above in Section 3.11G. I. The persistence and permanence of the potential adverse effects are finite. It is unlikely that humans or wildlife will come in contact with the residual contaminants. The contaminants have been steadily decreasing with remedial activities and time. Contaminants will likely attenuate to background conditions. 2) Potential adverse effects on surface water quality and beneficial uses: A. Mass estimate calculations suggest there may be up to approximately 50 to 100 gallons of TPH-G remaining in the soil beneath COE. The surface areas on and near the site are capped by structures, base rock, concrete or asphalt. Impact to surface water is unlikely. B. Hydrogeological characteristics of the facility and surrounding land are relatively uniform layers of sand-silt mixtures, sands and silts. The details are discussed in Section 2.0. C. Groundwater bearing and slope average N73°W at 0.0019 ft/ft as discussed in Subsection 2.3.2. Groundwater velocity is estimated to be 0.758 to 75.8 feet per year as discussed in Subsection 2.3.4. D. There are no groundwater users within a 1,600-foot radius of the COE site as discussed in Section 3.1. There are no surface waters within a 2,000-foot radius of the COE site. E. According to the USDA Soil Survey of San Joaquin County, California (McElhiney, M. A., 1992); the soils below the site are very deep, somewhat excessively drained, nearly level soil on dunes with 0 to 2 percent slopes. The details are discussed in Subsection 2.2. It is not likely that potential future uses of groundwater in the area will be impacted. F. It is unlikely surface water uses will change in the foreseeable future. G. According to the USDA Soil Survey of San Joaquin County, California (McElhiney, M. A., 1992); the soils below the site are very deep, somewhat excessively drained, nearly level soil on dunes with 0 to 2 percent slopes. The potential for health risks caused by human, wildlife, crops or vegetation exposure (dermal, ingestion or inhalation) is negligible due to unlikely contact --' with subsurface hydrogeology. V