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Page 3 Ms Margaret Lagono Quarterly Groundwater Monitoring Report - September 1996 (Third Quarter) October 28, 1996 3)Philip submitted a Remediation System Pilot Test Workplan, dated July 1, 1994, to the San Joaquin County Environmental Health Division describing proposed groundwater cleanup technologies These technologies include groundwater sparging combined with I soil venting Several sparge and vent wells have been installed to implement this remediation However, cleanup has been postponed due to pending changes in related California remediation guidelines Philip will continue groundwater monitoring until at least those changes have been established or results of natural biodegradation studies ' discussed in the "Recommendations" section below indicate otherwise MONITORING ACTIVITIES This quarterly groundwater monitoring and sampling event was performed between ' September 16 and 18, 1996 The depth to groundwater and the presence or absence of PSH was evaluated in each monitoring well Groundwater elevation measurements for this quarter are presented in Table 1 Historical groundwater elevation measurements are ' in Table 2 Groundwater samples were collected from all monitoring wells except MW-9, MW-11, . and MW-12 The purging/sampling pump malfunctioned, and because of the large volume ' of purge water required, Philip did not sample these wells However, Monitoring Wells MW-2, MW-5, and MW-7 are located near these non-sampled wells for reference During future monitoring events, Philip will use backup or alternative equipment if the I primary equipment fails Groundwater sampling procedures are presented in Appendix A Water sample field data sheets are presented in Appendix B ' The samples were analyzed in accordance with United States Environmental Protection Agency (USEPA) guidelines for TVH-G, and benzene, toluene, ethylbenzene, and total xylenes using USEPA Methods Modified 8015 and 602, respectively Western Environmental Science& Technology, located in Davis, California, performed the ' analyses Analytical results for this quarter are presented in Table 3 Historical analytical results are in Table 4 IQUARTERLY/HISTORICAL MONITORING RESULTS ' The groundwater elevations in the facility monitoring wells on September 16, 1996, ranged from -30 31 to -31 75 feet MSL (see Table 1) The groundwater levels in the wells decreased approximately 1 3 to 2 3 feet from the previous monitoring event ' Potentiometnc groundwater elevation contour maps for the current monitoring event are presented in Figure 3 As shown on the contour map, the estimated groundwater flow direction radiates outward from Monitoring Wells MW-1, MW-7, and MW 10 Based on the histoncal water level data(Table 2) and the configuration of the groundwater plume ' (Figures 4 and 5), the generalized flow direction is easterly to northeasterly 1 I