SITE INFORMATION AND CORRESPONDENCE 1993-1995

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James L. Tjosvold, P.E. February 23, 1995 Page 4 In summary, on-site well MW-5 would be deleted from the sampling program. New wells MW-17 and MW-19 would be monitored quarterly and existing perimeter wells MWAD and MW-6 would be sampled annually. The proposed revised program is described in Table 1. Zone C: The Workplan specifies that the parameters to be analyzed in Zone C wells will be analyzed for PNAs quarterly and one time for general minerals. The rationale was to evaluate concentrations of chemicals previously detected (PNAs) and evaluate general water quality(general minerals). PG&E recommends the following revisions to the monitoring program for Zone C wells: • Reduce the frequency of sampling from quarterly to annually in the Zone C well installed prior to the Phase III investigation(MW-13). This well has been sampled five times and annual analysis will be sufficient to monitor temporal changes. • Add BTEX analysis because of concentrations of benzene detected in MW-14 and MW-15, upgradient Zone C wells. Add analysis of barium and antimony for the reasons stated in the Zone A monitoring program. In summary, existing well MW-13 would be sampled annually and newly installed wells MW-14, MW-15 and MW-16 would be sampled quarterly. The proposed revised program is presented in Table 1. Please review the proposed revisions to the monitoring program for Zone A, Zone B and Zone C wells. We would like to discuss this proposal with your staff at our February 28, 1995 meeting and would like approval to implement this proposal prior to March 15, 1995. If you have any questions or require additional information, please call me at (415) 973-6254. 7 Patricia Sullivan Stockton Manufactured Gas Plant Site Project Manager