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observed in soil samples collected from the site. The distribution of petroleum constituents beneath the site has been evaluated and appears to be limited laterally to the immediate vicinity of the fonner tank pit. The highest concentrations were reported between 10 and 20 feet bgs and generally attenuate rapidly with depth. Only low concentrations of toluene (0.064 mg/kg) and xylenes (0.012 mg/kg) were detected at approximately 30 feet bgs in one boring, the maximum depth explored. Attempts were made to further advance a Geoprobe® unit in several of the borings; however, probe refusal was encountered at depths ranging from approximately 16 to 30 feet blas due to the hardness of the formation. The results of the subsurface investigation were summarized in Smith Technology's Summary Report, Subsurface Investigation, dated December 22, 1997. In April 1999, at the request of Public Health Services/Environmental Health Division (PHS/EHD) of San Joaquin County, ATC completed a receptor survey for the subject property. ATC reviewed PHS/E'HD 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 any groundwater wells located within a 2,000-foot radius of the site. This survey revealed 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 far Andrew and Edith Trust, for the Property at 1112 East Harding Way, Stockton, California, dated April 9, 1999. On April 11, 2000, a single soil boring (SB7) was advanced to annroximately_b5_,feet bgs to evaluate whether groundwater had been impacted at the subject site. Groundwater was initially encountered at approximately 45 feet bgs and a sample was subsequently collected from the soil boring using a Hydropunch® groundwater-sampling tool. In order to evaluate the vertical extent of contamination in the most cost-effective manner, the soil boring was further advanced to a total completion depth of 66.5 ft. bgs where field observations suggested the vertical extent of petroleum hydrocarbons had been realized. Analytical results and field observations indicated that soil and groundwater beneath the location of the former USTs were i acted by residual petro eum y rocarbon cons i uents. a vertical extent of impacted soil and groundwater 2 ---->appeared to be delineate owever, the lateral extent of petroleum hydrocarbon constituents at or near the groundwater interface was not completely determined. Additional work to further characterize the extent of contamination was requested by the PHS/EHD in correspondence dated H ° ? September 20, 2000. On November 15 and 16, 2001, an ATC geologist supervised the advancement of three soil borings to approximately 55 feet bgs. These borings were 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 MWl and MW3 at depths of 35 feet bgs contained trace concentrations of xylenes and TPHg, respectively. The samples collected from borings MW1 and MW3 at depths of 40 feet bgs did SA22493 veports\CAP.doc 2