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Voice 209 468-0337 Fax 209-468-3433 San Joaquin County Environmental Health Fac To: Peter J. Niemiec From: Mary Meays, Senior REHS Fax: (714) 577-2980 Pages: 2 Phone: (714) 577-2980 Date: November 10, 1997 Re: 4707 Pacific Ave Unocal CC: David Irey(209) 468- 0314 • Comments: Thank you for meeting today with representatives of San Joaquin County Environmental Health and the San Joaquin County District Attorney's office, it is unfortunate that a representative was not present with authority to address issues around which the office hearing was scheduled. As I indicated I will provide a list of directives which have not been complied with by Tosco on behalf of Unocal. 1. A work plan to install a minimum of four monitoring wells, to replace wells destroyed under permit and to provide the monitoring capabilities necessary to assess the shallow groundwater contamination. Groundwater levels have risen and some wells had screened intervals which are submerged greater than 20 feet. 2. A work plan to perform soil investigation to assess the effectiveness of the vapor extraction system. The system is using wells that have screened intervals which have presumably silted up and whose effectiveness is questionable. The response which was received, proposed a single boring very near a vapor extraction well with a depth less than the maximum depth of contamination evidenced at 50 feet bgs of 4,300 ppm TPH-gas and 17 ppm benzene. The vertical extent of the contamination remains uncharacterized. 3. A workplan to install air sparge wells to provide further cost effectiveness analysis of the groundwater extraction system proposed in the corrective action plan, but that has not yet been implemented. The response which was received, indicated that the groundwater plume appeared to have stabilized and was apparently shrinking. PHS/EHD subsequently responded that it was difficult to make such an assertion given the monitoring capabilities available at the site.