SITE INFORMATION AND CORRESPONDENCE_FILE 1

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'00 P--e Street, 1 0th Floor San F-arcisco. CA 94111 '415; 434-9400 • FAX C4151 434-1365 GEOMATRIX 7 November 1994 Project C2677A Ms. Wendy Cohen Regional Water Quality Control Board - Central Valley Region 3443 Routier Road, Suite A Sacramento, CA 95827-3098 Subject: Response to RWQCB Letter dated 18 October 1994 Dividend Property Tracy, CA Dear Ms. Cohen: Geomatrix Consultants, Inc. (Geomatrix) has prepared this letter on behalf of Chevron Pipe Line Company (CPLC) and Texaco Trading and Transportation, Inc. (TTTI) in response to the letter of 18 October 1994 from Mr. John Moody of your office that requested additional soil sampling and raised several other matters relating to further work at the Dividend Property. Mr. Moody and I discussed his comments in a telephone conversation on 31 October 1994, the substance of which is incorporated into this response. STOCKPILED SOIL Mr. Moody's letter stated that the detection limits for polynuclear aromatics (PNAs) and semi-volatile organic compounds (SVOCs) from the stockpiled soil analysis appeared high and additional analyses at lower detection limits were required to confirm that use of the soil as backfill material would not pose a threat to water quality. As he and I discussed on 31 October, the state of the practice for analysis of soil samples for PNAs or SVOCs is EPA Method 8270 (or equivalent), with practical quantitation limits of about 330 µg/kg. The quantitation limits can be lowered to about 200 µg/kg by quantitating the PNA fraction only (EPA Method 8270 or 8100). There are a few laboratories in the State of California (two that I know of) that will analyze soil samples for PNAs using EPA Method 8310, which can usually achieve detection limits of between 5 and 200 µg/kg depending on the specific PNA. These analyses are typically performed in support of risk-assessment activities, not for site characterization. Of course, analysis for PNAs by any of these methods may result in higher detection limits if there are interferences due to high concentrations of petroleum compounds present in the sample. The detection limits stated herein are typically for unaffected or slightly-affected soil samples. As Mr. Moody and I discussed, Geomatrix generally understands the 330 µg/kg detection limit for PNAs in soil is adequate for characterization and protective of groundwater, because PNAs have very low water solubilities and very high partitioning coefficients (Kw or Ka). As a result, PNAs sorb strongly to soil and do not enter the aqueous (dissolved) phase unless Geomatrix Consultants, Inc. Engineers Geologists,and Environmental Scientists