SITE INFORMATION AND CORRESPONDENCE

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Flag City Chevron 26 August 2002 6421 Capitol Avenue,Lodi - 2 - 3. The highest MtBE concentration on site was identified in monitoring well MW-8A,which is completed at 40 to 50 feet. MtBE was identified in MW-8A at 700 µg/1 in March 2002, and at 250 µg/1 in June 2002 after being non-detect for nine sampling events. AGE proposed to complete additional push probe borings near MW-8A to further define these detections, and we approved the work in our letter dated 20 May 2002. Please complete this additional investigation work in the third quarter of 2002, and include your findings in the Q3-2002 report. 4. Over the last two quarters, diesel detections were identified in fifteen of the small diameter multi-level monitoring wells. AGE's analytical lab reported that these diesel detections did not have typical diesel characteristics,and that the detected chromatogram peaks were probably the result of biological interference. AGE proposes to use silica gel for cleanup of future groundwater samples to eliminate the possibility of biological interference. Board staff do not agree to use silica gel cleanup of all water samples. Silica gel is known to remove polar compounds as well as breakdown products from weathered petroleum hydrocarbons. Therefore, if silica gel cleanup is to be used on water samples,please analyze the samples by EPA Method 8015M prior to and following silica gel cleanup such that the results can be compared. Provide appropriate chromatograms of analyzed samples for comparison. 5. Extraction well EX-1 was last sampled in October 2000, and the MtBE result was 56 µg/1. Board staff are aware that this well is a low producer and EW-2 is within 15 feet of the well;however,please purge and sample EX-1 and report results in the Q3-2002 report. 6. Please make a note in Table 7 under the analytical data for former Rocky's Domestic Well that the well was destroyed. AGE recommended reducing the existing groundwater monitoring program at the Flag City Chevron site due to the reduction in groundwater concentrations. Specifically,AGE recommends the following changes: RI. Transfer monitoring well MW-13 to the Three B's site; R2. Reduce sampling of the two CSA wells from quarterly to annually; R3. Transfer sampling of Three B's domestic well to the Three B's site; R4. Reduce analysis of methanol and ethanol from quarterly to annually; R5. Eliminate ethylene dibromide and 1,2-dichloroethane from the monitoring program; and R6. Reduce analysis of nitrates,turbidity, and total dissolved solids at the effluent,R-1, and R-2 from quarterly to annually. Board staff agree to transfer monitoring well MW-13 to the Three B's site; however,we do not agree to reduce sampling of the two CSA wells from quarterly to annually. Due to the "diesel" detections in monitoring wells MW-10A,MW-10C,MW-101), and MW-10E,Board staff believe that quarterly monitoring at both CSA wells is warranted. Recommendations R3 through R5 above are requirements of the monitoring and sampling section of C&A No. 5-00-700, and Board staff will address these recommendations under separate cover. Flag City Chevron shall not implement any changes to the C&A No.5-00-700 monitoring and sampling requirements until a revision or suspension of the requirements is issued by the Executive Officer.