SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Chevron#9-6171 2 22 February 2005 6633 Pacific Ave., Stockton 2. The Report's unnumbered table, titled Groundwater Monitoring Data and Analytical Results, shows that 4 of the 6 "dry"monitoring wells that were not sampled this quarter, have reported insufficient water for multiple quarters (Figure 2). It appears that your samplers, Gettler-Ryan, do not sample if the wells contain less than a foot and a half of measurable water. Monitoring Well MW-8 MW-9 MW-10 MW-12 MW-13 MW-14 (depth) (39.02' 38.99' (38.65' 39.75 38.63' 38.41' Consecutive Quarters not sampled 4 5 4 2 1 1 MW-8, -9, and—10 are onsite wells. MW-12, -13 and—14 are downgradient wells across Pacific Avenue. I request that Secor conduct an evaluation to determine whether the'dry wells" should be replaced, include those recommendations in the next quarterly monitoring report, and provide a Work Plan with current well construction details and a schedule for the work if replacement wells are needed. 3. It appears from the data table that several petroleum hydrocarbon constituents, which were previously tested, have been removed from the monitoring program after several quarters of non-detect results. The analytical method detection limits (MDLs) reported for those constituents, 2 µg/L, is too high for comparison to water quality objectives. Fuel oxygenates, including MtBE, and fuel additives ethylene dibromide (EDB) and 1,2-Dichloroethane (1,2-DCA) should be reported at MDLs of 0.5 µg/L. Therefore, during the next quarterly monitoring event, you will also test all wells for fuel oxygenates, EDB and 1,2-DCA; and report them at the MDLs of 0.5 µg/L. If detection of any constituent results from the lower MDLs, then analyses for those constituents will resume quarterly for those wells. 4. As stated above, the field technician noted a problem with sampling access for MW-4 in Gettler- Ryan's Well Monitoring/Sampling Field Data Sheet, which says "Inaccessible— buried under landscaping". As a result, MW-4 was not sampled for the first time during this quarter. Please work with the Chevron station to uncover MW-4 and determine whether it is damaged. If MW-4 has been damaged, then destroy it under permit from San Joaquin County Environmental Health Department, in accordance with their ordinance. If damaged include a Work Plan for replacement of MW-4 with the next quarterly report. 5. All future reports and workplans are to follow the Tri-Regional Recommendations for Preliminary Investigation and Evaluation of Underground Storage Tank Sites and Appendix A (Tri-Regionals). Please refer to the Internet link under the header of this letter to download the Tri-Regionals. The Tri-Regionals call for quarterly reports that include isoconcentration maps of each contaminant, as is relevant to the lateral extent of contamination, and geologic cross sections showing the vertical extent of contamination. 6. All subsequent quarterly reports must include the well screen intervals for each monitoring well in the data table.