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V 1117 Lone Palm Ave,Suite 201 Modesto,CA 95351 Phone:209-579-2221 r (YVJ%TC Fax: 209-579-2225 borings; however, probe refusal was encountered at depths ranging from approximately 16 to 30 feet bgs due to stiff soils. The results of the subsurface investigation are summarized in Smith Technology's Summary Report, Subsurface Investigation, dated December 22, 1997. In April 1999, at the request of the Public Health Services/Environmental Health Division (PHS/EHD) of San Joaquin County, ATC completed a receptor survey for the subject property. ATC reviewed PHS/EHD groundwater well construction logs, Department of Water Resources (DWR) groundwater well construction logs, and conducted a site walk in the vicinity of the site to identify groundwater wells located within a 2,000-foot radius of the site. This survey " identified 14 wells located within approximately 2,000 feet of the site. The closest of these wells is located approximately 800 feet upgradient of the project site. The receptor survey findings are summarized in ATC's Well Survey for Andrew and Edith Trust,for the Property at 1112 East r Harding Way, Stockton, California, dated April 9, 1999. On April 11, 2000, a single soil boring (SB7) was advanced to approximately 65 feet bgs to evaluate the groundwater quality. Groundwater was initially encountered at approximately 45 r feet bgs and a sample was subsequently collected from the soil boring using a Hydropunch® groundwater-sampling tool. To evaluate the vertical extent of contamination in the most cost- effective manner, the soil boring was advanced to a total completion depth of 66.5 feet bgs `+ where field observations suggested the vertical extent of the petroleum hydrocarbons had been realized. Analytical results and field observations indicated that soil and groundwater beneath the former USTs were impacted by residual petroleum hydrocarbon constituents. The vertical extent of impacted soil and groundwater appeared to be assessed. However, the lateral extent of petroleum hydrocarbon constituents at or near the groundwater interface was not completely assessed. Additional work to further characterize the extent of contamination was requested by `" the PHS/EHD in correspondence dated September 20,2000. On November 15 and 16, 2001, an ATC geologist supervised the advancement of three soil borings to approximately 54 to 55 feet bgs. These borings were then completed as groundwater monitoring wells MW1, MW2, and MW3. The soil sample collected from boring MW2 at a depth of 35.5 feet bgs contained the highest concentrations of TPHg, ethyl benzene, and xylenes. The soil samples collected from boring MW2 at depths of 30 feet bgs and 55 feet bgs contained only trace concentrations of TPHg, ethyl benzene, and/or xylenes. The soil samples collected from borings MW 1 and MW3 at a depth of 35 feet bgs contained trace concentrations of xylenes �+ and TPHg, respectively. The samples collected from borings MW 1 and MW3 at a depth of 40 feet bgs did not contain detectable concentrations of TPHg or BTEX. Methyl tertiary butyl ether (MTBE), t-amyl methyl ether (TAME), t-butanol (TBA), ethyl t-butyl ether (ETBE), di- bw isopropyl ether (DIPE), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) concentrations were less than the laboratory detection limit for each compound in soil samples collected from borings MW 1, MW2, and MW3. r s:\environmental\22493\reports\feasibility.doc 2 V r