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Chevron <br /> August 25, 1998 � Chevron <br /> Chevron Pipe Line Company <br /> Mr. Michael J. Infurna, Jr. 4000 Executive Parkway,Suite 400 <br /> San Joaquin County Public Health Services San Ramon,CA 94583 <br /> Environmental Health Division P.O.Box 6059 <br /> San Ramon,CA 94583-0759 <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Soil and Groundwater Investigation and Site Status Report <br /> Surland Homes Property <br /> Tracy, California <br /> Dear Mr. Infuma: <br /> Enclosed please find the subject report for your review. The report summarizes the soil <br /> and groundwater assessment performed by Geomatrix Consultants, Inc. (Geomatrix), on <br /> behalf of Chevron Pipe Line Company (CPL), at the Surland Homes Property in Tracy, <br /> California(the site). <br /> Based on field observations and analytical laboratory analyses performed on the soil and <br /> groundwater samples collected from the site, it appears that petroleum hydrocarbons (i.e., <br /> weathered crude oil)have impacted the site subsurface. During the July 1998 fieldwork <br /> the lateral and vertical extent of the petroleum hydrocarbon-affected soil was assessed. <br /> Benzene was not detected in any of the soil or grab groundwater samples; toluene, <br /> ethylbenzene, xylenes, and polynuclear aromatic hydrocarbons (PAHs)were detected at <br /> low concentrations in some of the soil and grab groundwater samples. The potential risk <br /> posed by toluene, ethylbenzene, xylenes, and the detected PAHs in soil at the site was <br /> evaluated based on a comparison to United States Environmental Protection Agency <br /> (U.S. EPA) Region IX Preliminary Remediation Goals(PRGs). U.S. EPA Region IX has <br /> devel,?Fed PRGs for residential soil based on an excess cancer risk of one-in-one million <br /> (1x10- ) or a hazard index for noncarcinogenic risk of 1 (U.S. EPA Region IX). Based on <br /> the comparison of the concentrations of toluene, ethylbenzene, xylenes, and PAHs to <br /> their respective PRGs, the presence of these constituents in site soil does not pose an <br /> unacceptable risk to future on-site residents. These data indicate that future use of the <br /> site for residential purposes should not be restricted due to past impacts by petroleum <br /> hydrocarbons. <br /> Based on the groundwater data collected, it appears that the residual petroleum present in <br /> the soil is not providing a significant source of dissolved petroleum constituents to <br /> groundwater. Groundwater samples collected from the two locations in the assumed <br /> downgradient direction from affected soil did not contain dissolved petroleum at <br /> concentrations above water quality objectives that have been established by the <br /> California Regional Water Quality Control Board—Central Valley (RWQCB) at similar <br /> sites (such as the neighboring Dividend property). Total petroleum hydrocarbons (TPH) <br />