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r APPENDIX A PREVIOUS INVESTIGATION SUMMARY Blaine Tech Services, Inc. In February 1988, Chevron U S A. Products Company (Chevron) contracted Blaine Tech Services, Inc (Blaine) to perform soil sampling and project supervision for service station demolition and underground storage tank (UST) removal activities Blaine performed soil sampling associated with the demolition of the Chevron service station building and product islands, and removal of four USTs from the site (three fiberglass gasoline USTs [10,000 gallons each] and one steel used oil UST [1,000 gallons]) Blaine reported that no holes were observed in any of the four tanks removed One soil sample was taken from the used oil UST pit The soil sample taken from the used oil tank pit was analyzed for the pres- ence of high and low boiling point hydrocarbons, EPA Methods 8010/8020 constituents and benzene, toluene, ethylbenzene, and xylenes (BTEX compounds) Laboratory analysis of the soil sample taken from the used oil UST pit revealed 26 parts per million (ppm) high boiling point hydrocarbons, 10 ppm low boiling point hydrocarbons and non-detectable amounts of BTEX compounds and EPA Methods 8010/8020 constituents After removing the three 10,000 gallon USTs, Blaine overexcavated the northeast portion of the tank pit (location of the three 10,000-gallon tanks) vertically to a depth of 25 feet below ground surface (bgs) One soil sample was taken from the bottom of the UST excavation The sample collected from the 10,000-gallon UST pit contained high boding point hydrocarbons detected at 55 ppm, low boiling point hydrocarbons at 340 ppm, toluene at 28 ppm, ethylbenzene at 12 ppm, and xylenes at 26 ppm Benzene was not detected in the 10,000-gallon UST pit soil sample Groundwater was not encountered during excavation activities Blame has resumed quarterly groundwater monitoring of site wells since January 1995 EA Engineering, Science, and Technology, Inc. In November 1987, EA Engineering, Science, and Technology, Inc (EA) installed ten shallow vapor probes throughout the site and conducted a soil vapor containment assessment No significant petroleum hydrocarbon contamination was detected at the site, thus no further action was recommended at the tine 3201337B/CAP AMD DOC A- 1 November 30 1995