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x Mr Kyle Christie Project 0805-140 01 February 13, 1995 Page 2 In March 1992 EA Engineering, Science Technology (EA) observed removal of the oil-water separator/clarifier (EA Engineering, Science and Technology, August 1992, Report 80633 01). EA collected one soil sample from beneath the former oil-water separator and one sample from the concrete Analytical results from the soil samples indicated that oil grease (quantified as total oil and grease [TOG]) was present Concentration of volatile organic compounds, senu-volatile organic compounds, and polychlorinated biphenyls were below detection limits Total metals were also below detection hnuts with the exception of arsenic and barium which were detected at concentrations of 0 0051 and 012 parts per million, respectively(see Attachment A) On March 2, 1992, RESNA conducted a vapor extraction test at the site (RESNA, June 15, 1992, Report 300045) Results of the test indicated that soil beneath the site can be remediated by vapor extraction and the evaluated radius of influence was 30 feet GROUNDWATER MONITORING, FOURTH QUARTER 1994 Groundwater Technology, Inc , (GTI) Concord, California, was contracted by ARCO to conduct the old work at the site, GTI subsequently forwarded their field notes and the laboratory reports to EMCON Field work included measuring depths to water and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the direction and gradient of groundwater flow beneath the site • On December 2, 1994, a technician from GTI measured the depth to water and collected groundwater samples from monitoring wells MW 1 through MW-6 for subjective and laboratory analyses The field methods and procedures used are presented m an Attachment A The technician did not observe floating product or product sheen on samples collected from the wells (see Table 1) The surveyed elevations of the top of casing and the depth to groundwater measurements (summarized in Table 1) were used to evaluate the potentiometric surface beneath the site On December 2, 1994, the direction of groundwater flow was toward the east with a gradient of approximately 0 003 (see Figure 3) The direction of groundwater flow Is consistent with previous sampling events Groundwater elevations increased approximately 0 83 foot from the previous sampling event(September 1994) Groundwater samples from each well were analyzed for total petroleum hydrocarbons as gasoline (TPHG), and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency Methods 5030/DHS/LUFr and 5030/8020, respectively The samples were analyzed at National Environmental Testing, Inc , in Santa Rosa, Cahfornia. The results of these analyses are summarized in Table 1 Copies of the laboratory analysts reports are Attachment A Results of analyses indicated TPHG were detected in groundwater samples collected from wells . MW-1 and MW-5 at a concentration of 60 parts per bdhon (ppb) and 2,200 ppb, respectively Benzene was detected at a concentration of 3 0 ppb (well MW-1) and 380 ppb (well MW-5) TPHG and BTEX were not detected in wells MW-2, MW-3, MW-4 and MW-6 Concentrations of TPHG and benzene are shown on Figure 2 SAC 1N Ipl010805108051400 Ibm-951mam 4