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Mr Kyle Christie March 1, 1996 Page 2 10 All groundwater samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons as gasoline (TPH-G) by U S Environmental Protection Agency(EPA)Method 5030/8020, and 8015 Modified Results and Discussion Groundwater flow on December 5, 1995 was to the northeast under an average hydraulic gradient ranging from 0 0002 on-site, to 0 001 northeast of the site (Figure 1) The groundwater under the site is slightly depressed, resulting from extraction of groundwater by the on-site remediation system (discussed below) Summaries of depth-to-water measurements and calculated groundwater elevations are presented in Table 1 Water-level elevations in Table 1 are corrected for the presence of free product Since groundwater monitoring began in 1989, the general groundwater flow direction has been to the northeast at this site, under hydraulic gradients ranging from 0 001 to 0 005 Table 2 lists historical groundwater flow directions and hydraulic gradients for this site Depth-to-water on December 5, 1995 ranged from 13.64 feet below the top of the well casing (TOC) in well PR-2, to 16 34 feet below TOC sn well E-I 1. Well E-10 contained approximately 0 37 feet of free product on December 5, 1995 Since the Iast quarterly monitoring event (September 1995), water-level elevations in all monitoring wells have decreased an average of 0 42 feet Benzene was not detected in wells E-12 and MW-4, but was detected in wells E-2, E-8, E-9, E-11, BHD-1, and MW-5 at concentrations ranging from 2 8 micrograms per liter(pgfL) in well E-8, to 960 WL in well E-9 With the exception of wells E-2, E-I 1, BHD-1, and MW-5, these results are consistent with previously reported results The benzene concentrations identified in wells E-2, E-11, and BHD-I are the lowest they been since sampling began in 1988 The concentration of benzene in well MW-5 is the highest it has been since sampling of this well began in March 1995 TPH-G was not detected in wells E-12 and MW-4, but was detected in wells E-2, E-8, E-9, E-11, BHD-1, and MW-5 at concentrations ranging from 150 pg/L in well E-8, to 45,000 pg/L in well E-9 These results are consistent with previous results with the exception of well MW-5 The TPH-G concentration is the highest it has been since sampling of this well began in March 1995 Analytical results of groundwater samples are summarized in Table 3 The complete laboratory report for the sampling event is presented in Exhibit A Figure 2 presents TPH-G and BTEX concentrations for this sampling event The hydrocarbon concentrations detected in BHD-1 are thought to be attributed to the Chevron station across the street from the ARCO site Chevron's well MW-1 is located approximately 30 feet to the north of well BHD-1 and near Chevron's former underground storage tank location Use or disclosure of data continued on this sheet is subject to the restriction specified at the beginning of this document 206aREPORTSv3TH95QTR DOC