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V � A S S O C I A T E S I N C ' reported between 10 and 20 ft. 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 ft. bgs, the maximum depth explored. Attempts were made to further advance ' the Geoprobe unit in several of the borings, however probe refusal was encountered at depths ranging from approximately 16 to 30 ft. bgs 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 PHS/EHD, ATC completed a receptor survey for the subject property. ATC reviewed PHSIEHD groundwater well construction logs, Department of Water Resources (DWR) groundwater well construction logs, and conducted a site walk in the vicinity 1 of the site to identify any groundwater wells located within a 2,000-foot radius of the site. This survey revealed fourteen wells located within. approximately 2,000 ft. of the site. The closest of these wells is located approximately 800 ft. upgradient of the project site. The receptor survey ' findings are summarized in ATC's "Well Survey", dated April 9, 1999. In October 1999, ATC submitted a "Closure Report" for the site that evaluated available data and ' requested No Further Action (NFA). PHSIEHS subsequently submitted a "Case Closure Summary" to California Regional Water Quality Control Board (RWQCB) for site closure. However, a "Nonoccurrence with No Further Action Required" letter dated February 3, 2000, was issued by the RWQCB. PHS/EHD, in their correspondence dated February 11, 2000, requested additional work be performed to investigate the potential for groundwater contamination at the subject site. 2.0 METHODS AND PROCEDURES To evaluate the whether groundwater had been impacted at the subject site, a single soil boring (SB7) was advanced immediately to the south of the western-most former 1,000-gallon UST ' (Figure 2). Soil samples previously collected from borings advanced in the vicinity of this location contained the highest detectable concentrations of petroleum hydrocarbons. All field activities were performed in accordance with ATC's February 28, 2000 Workplan for ' Supplemental Subsurface Investigation at Eggiman's Hydraulic Garage at 1112 East Harding Way, Stockton, California. The workplan was approved by PHS/EHD on March 29, 2000. ' 2.1 Soil Borin Advancement and Sam lin ' Drilling was conducted on April 11, 2000, by V & W Drilling (State C57 license no. 720904) utilizing a hollow stem auger drill rig. Soil boring SB7 was advanced to approximately 65 ft. bgs. Soil samples were collected at five-foot intervals using a 2-inch diameter split-spoon sampler containing three brass tubes. A field geologist logged drill cuttings and soil samples utilizing the Unified Soil Classification System. Descriptions of soil types encountered and . sample collection intervals are included on the boring log contained in Appendix A. A flame- ' wA92054.0001VeportslsumsbTdoc 2 1