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STATE OF CALIFORNIA- Environmental Protection Agency PETE WILSON, Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD . Ti 9 d` "•°°w CENTRAL VALLEY REGION 3443 Routier Road, Suite A Sacramento, CA 95827-3098 PHONE: (916) 255-3000 () 1, 20 P'11 1 �' � '`•n:.�`'� FAX: (916) 255-3015 18 October 1994 Mr. Don O. Culbertson Environmental Specialist Chevron Pipeline Company 5080 California Ave., Suite 400 Bakersfield, CA 93309-1671 REQUEST FOR WORK PLAN: CHEVRON PIPELINE COMPANY, DIVIDE1ND PROPERTY, TRACY, SAN JOAQUIN COUNTY We have reviewed your plans for further soil sampling contained in the 13 July 1994 Work Plan for Screening Health Risk Assessment (SHRA), prepared by your consultant, Geomatrix Consultants. We also have reviewed the analytical results of samples from drums and soil stockpiles and from quarterly ground water monitoring. You will need the approval of the Department of Toxic Substances Control (DTSC) on the SHRA work plan. Stockpiled Soil Although the analytical results of sampling the drummed and stockpiled soil showed no BTEX (benzene, toluene, ethylbenzene, and xylenes), SVOCs (semi-volatile organic compounds), PNAs (polynuclear aromatic compounds) or PCBs (polychlorinated biphenyls), the reporting limits for the SVOCs and PNAs were relatively high, ranging from 200 to 400 µg/kg. Detection limits of 50 to 100 Ag/kg should be achievable using current laboratory methods. Therefore, additional sampling of the trench bottoms and stockpiled material is needed at lower detection limits to confirm the results. Provided the chemical concentrations will not pose a threat to water quality, the stockpiled soil may then be used for filling in the trenches and for grading. As agreed in our 23 September 1994 meeting, the drummed soil will be removed from the site and disposed of at a landfill. Extent of Contamination Although the proposal to install 21 soil borings paired on either side of the fence along the Southern Pacific right-of-way may be laterally representative of the site for the health risk assessment, it may not define the full lateral extent of soil contamination. Therefore, additional soil borings may be required beyond those proposed. We will determine the need for additional soil sampling after we review the results of the current phase of work. Page 5 of the SHRA work plan describes the oil in the subsurface as "weathered crude or Bunker C", which has been "fingerprinted" from previous soil and free product analysis. PNAs and BTEX are identified as the primary chemicals of concern, since they are known breakdown products of weathered crude or Bunker C. However, the selection of soil samples for laboratory analysis is based upon the levels of TPH, rather than its breakdown products, and there is a possibility that the soil samples selected may not be representative of the primary chemicals of concern. Therefore, the samples also should be screened using a photoionization detector or similar device to detect VOCs such as BTEX.