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i M. r"IN r Mr. Kyle Christie December 9, 1988 Page 3 The contour snap prepared by Brown and Caldwell for May 2, 1988, benzene concentrations in groundwater was found to contain an error. The corrected May 2, 1999' . map is shown on Figure 1. A contour map for August 26, 1988, benzene concentrations in groundwater is shown on Figure 2. The concentrations of ethylbenzetie are above DHS action levels in monitoring wells BHD- 1 and E-9. The concentrations of toluene and xylene are above,•. DHS action levels in monitorirg wells BHD-1, E-5, and E-9. Recovery System Water Quality Sample T-1, collected from the discharge line of the':'.•covery system, was analyzed for TPH at Eureka Laboratories in Sacramento. Results are summarized in Table 1. Complete laboratory reports are enclosed. TPH was not detected in the sample taken from the discharge line of the recovery system. No action level has yet been established for TPH. BETX was not analyzed from Sample T 1 during this sampling episode because of an error during sampling. Groundwater Flow Groundwater levels at the site are being measured in each well on a weekly basis. The levels are measured with an electronic water level indicator to determine groundwater elevations relative to top of casing elevations. Since late April 1988, the groundwater flow direction has been influenced by the recovery system, which has been functioning ; continuously since early April. A groundwater contour map for August 30, 1988 (the measurements taken closest to the date of sampling), is shown on Figure 3. Table 3 summarizes the August 30, 1988, measurements. The contour map shows that groundwater flow is still being influenced by the recovery system. Conclusions The groundwater samples collected during the summer quarter, 1988, show that benzene concentrations are increasing in wells BHD-1, E-8, and E-9. Monitoring well E-5, located closest to the recovery system, showed a decrease. Monitoring wells PR-1 and PR-2 have never shown any benzene. The increase in benzene concentrations in momioring wells Bl-1D-1 and E-9 suggest that contamination is being pulled by the recovery system toward the site from another source. A service station located north of the site, across Benjamin Holt Drive, may be the source of the contamination. The increase in benzene concentrations in monitoring well E-8 cannot be fully explained at this time, but may be J. the result of (1) a sampling error, or (2) contamination from an off-site source. The presence of toluene and xylene in monitoring well PR-2 is near the detection limit of the and could be the result of a sampling error or a laboratory laboratory analytical equipment, error. y� BROWN AND CALDWELL 72 SMEF.TSACMAK4ENTO.CALIFORNLAtbai4-7=-M:61444*23 �S ,