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4 TABLE 2 Groundwater Analytical Results Second Quarter 1995 Monitoring Event 7759 S. Airport Way Stockton, California Monitor Well Benzene Toluene Ethylbenzene Xylene TPH-D ID µg/L ug/L ugIL 'UgR- AgR- MW-1 NDro s1 NDro s) NDro 5) NDro 5) 76 MW-2 NDro s) NDro 51 NDro s) NDro s) ND(5m MW-3 NDro ro NDro n NDro 51 NDro ro 690 MW-41 ND(0 5) ND(o s) ND,,,) NDro.51 660 ND - Not detected above laboratory quantification limit indicated in parenthesis ' `MW-4 is a blind duplicate sample of MW-3 As shown in the table, benzene, toluene, ethylbenzene and xylenes (BTEX) were not detected at the respective detection levels in all wells nor in the blind duplicate sample (MW-4). TPH-D was detected in two of three wells at the site, MW-1 at 76 µg11 and MW-3 at 690 µg11. MW-4, a blind duplicate of MW-3, indicated the repeatability of the analysis was within 5 percent. 4.0 SUMMARY AND RECOMMENDATIONS The following is a summaryof the results of the Second Quarter 1995 groundwater sampling event at 7759 South Airport Way, Stockton • Groundwater flow in the vicinity of the former USTs has shown a slight rotation toward the north by northwest • This is the first of three quarterly sampling events at the site in which TPH constituents were detected in any of these wells The highest concentration was detected in MW-3, which is approximately 40 feet in an upgradient direction of the former tanks This may indicate that TPH-D is coming from another I upgradient source More likely, the increase may be from the rising groundwater levels which allows TPH-D constituents in soil to be released into the groundwater IBased on the above summary of results, WESTON recommends • Groundwater monitoring continue for two additional quarters (fourth calendar quarter 1995) after which the monitoring program can be re-evaluated to determine the necessity for future activities at the site, if any L SPROJECCSLSANJOQtTMADIND QTR 6 31 July 1995