SITE INFORMATION AND CORRESPONDENCE FILE 1

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Chevmn Chevron U.S.A. Products Company RE I74 2410 Camino Ramon,San Ramon,California•Phone (510)842-9 AUG 2 7 1992 Mail Address: P.O.Boz 5004,San Ramon,CA 94583-0804 August 26; 1992 ENVIRONMENTAL HEALTH PERMIfi1WVIP Mr. J. Lawrence Pearson California Regional Water Quality Control Board Central Valley Region 3443 Routier Road, Suite A Sacramento, CA 95825-3098 Re: Former Chevron Service Station #94054 2103 Country Club Blvd., Stockton Dear Mr. Pearson: This letter is being submitted as an addendum to the Pacific Environmental Group, Inc.'s Work Plan dated July 17, 1989, for the above referenced site as per a telephone conversation with Mr. Boggs on August 25, 1992. The modifications to the work plan are warranted due to the change in ground water flow direction. A revised map is attached plotting these locations. The changes in the scope of work are as follows: * Installation of four(4) two-inch diameter ground water monitoring wells to delineate the extent of the hydrocarbon plume. - One ground water monitoring well will be placed within 10-feet of the former waste oil tank in the down-gradient direction as well as up-gradient of the former tank complex. -Two wells will be located off-site cross-gradient of the former tank complex. - One well will be located off-site directly down-gradient of the site Well locations are approximate and may require adjustment to account for overhead and underground utilities. * During the development of the newly installed wells, the existing wells will be redeveloped to remove approximately 5-feet of sedimentation buildup. * Ground water sampling and analysis of all previously existing and newly installed monitoring wells will be performed and will continue on a quarterly basis. * The vertical and horizontal extent of hydrocarbon-affected soils will be defined by implementation of a soil coring program. A work plan will be prepared outlining the scope of work for this program and will be submitted to your office by September 9, 1992. * Previous file reviews have indicated that releases of petroleum hydrocarbons have occurred in the subsurface at adjacent properties. An agency file review will be conducted to investigate if assessment activities have been performed. * A report will be prepared documenting the results of the ground water monitoring well installation/sampling, soil coring program and file review. It is anticipated that this report will be submitted within thirty (30) days after receipt of the analytical data.