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r a REMEDIATION CONFIRMATION SAMPLING RESULTS AND CLOSURE RECOMMENDATION REPORT (March 1994 Revision) 909 YVesi Hammer Lane Sloeldon Caldomm • In February 1986, GTI supervised the excavation of three 8,000-gallon fuel tanks and one 500-gallon used-oil tank Six soil samples collected from the UST basins contained petroleum hydrocarbon concentrations up to 4,600 parts-per-million (ppm) Analytical results are summarized in Table 4 • In November 1986, GTI drilled and sampled well MW-3 Table 4 summarizes analytical results of soil samples collected from the well boring The well log and construction details are included in Appendix H Groundwater samples were collected from all wells for the first time Groundwater analytical results are summarized in Table 3 The results indicated dissolved hydrocarbons in all three wells • In June 1987, GTI drilled and sampled wells MW-4 and MW-5 The well logs and construction details are included in Appendix H Soil and Groundwater analytical results are included in Tables 4 and 3, respectively No hydrocarbons were reported in the soil samples Dissolved hydrocarbons were present in the groundwater samples • In November and December 1987, EA Engineering, Science and Technology (EA) of Lafayette, California, conducted a soil vapor survey at the site The results are included in Appendix I No significant hydrocarbon concentrations were reported except from vapors collected from monitoring wells MW-1, MW-3 and MW-4 • In July 1989, EA drilled and sampled three soil borings on site (SB-5 through SB-7) Soil sampling analytical results are summarized in Table 5 No total petroleum hydrocarbons as gasoline were detected except far 1 6 ppm in SB-7 at 30 5 feet • In July 1989, EA conducted a search of California Department of Water Resources records for water supply wells within 2,500 feet of the site Results of this search are included as Appendix G • In March 1990, EVAX Technologies (EVAX) conducted another soil vapor survey and a vapor extraction performance test, for remediation system design The results of the survey and testing, included in Appendix I, indicated up to 19,000 ppm of volatile hydrocarbons beneath the former UST basin • In August 1990, EA drilled and installed wells MW-6, MW-7, and MW-8 in the vicinities of wells MW-3, MW-4, and MW-5, respectively, because the latter went dry (Figure 2) The well logs and construction details are included in Appendix H Soil sampling analytical results are summarized in Table 5 No hydrocarbons were reported from any of the soil samples analyzed Dissolved hydrocarbons were reported only in the groundwater sample from MW-6 93.005C OMR 2