SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Chevron Chevron Chevron Pipe Line Company 4000 Executive Parkway,Suite 400 5 April 1995 San Ramon,CA 94583 P0.Box 5059 San Ramon,CA 94583-0959 Ms. Wendy Cohen California Regional Water Quality Control Board Central Valley Region 3443 Routier Road, Suite A Sacramento, California 95872-3098 APR 10 TECHNICAL MEMORANDUM CHEVRON PIPELINE COMPANY ENVIRONMENTAL HEALTH DIVIDEND PROPERTY,TRACY, CALIFORNIA PERMIT/SERVICES r Dear Ms. Cohen: Please find enclosed the technical memorandum, dated 8 March 1995, on the topic of detections of total petroleum hydrocarbons (TPH) in groundwater, presented on behalf of Chevron Pipe Line Company (CPL) by Geomatrix Consultants,Inc. (Geomatrix). This memorandum was developed in response to the general question about the sources of TPH detections in groundwater samples and how TPH results may not represent dissolved-phase concentrations of petroleum hydrocarbons in groundwater. This concept and its importance was first discussed in our meeting for the Dividend Property, Tracy, California, held on 23 September 1994. The information included in this memorandum is presented by CPL and Geomatrix in order to provide clarity and understanding with respect to the topic of measuring dissolved petroleum constituents in groundwater, as analyzed for total petroleum hydrocarbons.We believe that the discussion is very informative and provides an in-depth review of what has in the past been a complex topic. The,technical material presented in the memorandum has been reviewed by Chevron's in-house research group (Chevron Research and Technology Company; CRTC) and outside experts. Over the past two years, Geomatrix has conducted extensive research directed toward a better understanding of the fate and measurement of petroleum hydrocarbon constituents in the subsurface. CPL has implemented the recommendations proposed by Geomatrix in this memorandum for the first quarter 1995 monitoring event at the Dividend Property. In addition to the analyses required in the RWQCB Monitoring and Reporting Program, (MRP)No. 95-801, dated 5 January, 1995, filtered pairs of groundwater samples have been collected at selected wells to be analyzed for TPH (8015) and TRPH (418.1). Furthermore, the laboratory was instructed to perform a silica gel cleanup on the filtered samples for the Method 8015. All samples were submitted blind to the laboratory to exclude the potential for bias.