SITE INFORMATION AND CORRESPONDENCE_FILE 1

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`/ E Chevron �r Chevron Chevron Products Company 6001 Bollinger Canyon Road February 28, 1997 Building L San Ramon,CA 94583 P.O.Box 6004 San Ramon,CA 94583-0904 Ms.Mary Meays Marketing—Sales West San Joaquin County Environmental Health Phone 510 842-9500 P.O. Box 388 Stockton, CA 95201-0388 Re: Chevron Station#9-6171,6633 Pacific Avenue, Stockton, CA Attached groundwater monitoring report(Gettler-Ryan, 12/16/96) Dear Ms. Meays: Please find attached a report dated December 16, 1996,which was prepared by Chevron's consultant, Gettler-Ryan, Inc. (Gettler-Ryan), to describe the results of groundwater monitoring that was performed at the subject site during November, 1996. In November Gettler-Ryan gauged and sampled all six site-related wells. All groundwater samples were analyzed for the presence of TPHGas,BTEX constituents,MTBE,and various dissolved ions. In addition, split samples were analyzed for volatile organic compounds(EPA method 8260)to assess the distribution of chlorinated compounds beneath the subject site.However,these results have not been provided to Chevron by the consultant representing the drycleaners investigation. The measured direction of groundwater flow was toward the east. There were discrete peaks measured and reported within the range of TPHGas at wells MW-2 through MW-6.However,these detections more than likely represent interference caused by chlorinated compounds that are known to exist in groundwater beneath the subject site.Except for wells MW-3 and MW-7,there were no dissolved hydrocarbons detected in groundwater. Only 0.82 ppb of toluene was detected at well MW-3. There was TPHGas and BTEX constituents detected at well MW-7. The presence of dissolved motor fuel hydrocarbons is unusual at this location and their presence will be verified during the next monitoring event. There were no detectable concentrations of MTBE measured at any of the site-related wells. A review of present groundwater conditions has revealed that groundwater monitoring well screens are submerged. The submerged conditions have existed since approximately March, 1995. In some cases earlier. However, certain trends have been established prior to the submergence of well screens. The direction of groundwater flow has consistently been to the east-southeast. TPHGas concentrations have been inconclusive as to the presence of motor fuel hydrocarbons due to the presence of chlorinated compounds. Except for detections at well MW-2,BTEX levels have been consistently absent or at trace concentrations intermittently. The levels at MW-2 have been relatively high in the past but,have also exhibited decreasing trends prior to the screen becoming submerged. All of these trends combined with the absence of any quantifiable source of hydrocarbons in the subsurface support a decision to close the case. Chevron's consultant, Pacific Environmental Group, Inc.,is currently revising a closure summary report for resubmittal to your agency. In the meantime, Chevron would like to propose the following modifications to the monitoring and reporting program currently in effect at the subject site: