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Department of Toxic Substances Control <br /> Edwin F. Lowry, Director <br /> 400 P. Street, P. O. Box 806 <br /> Sacramento, California 95812-0806 <br /> Winston H. Hickox Gray Davis <br /> Secretary for Governor <br /> Environmental <br /> Protection MEMORANDUM <br /> TO: Ms. Dink Mather <br /> Site Mitigation Branch, Region 1 <br /> 10151 Croydon Way <br /> Sacramento, California 95827-2106 <br /> FROM: David L. Bent', Ph.D. <br /> � <br /> Staff Toxicologist <br /> Human and Ecological Risk Division (HERD) <br /> DATE: March 14, 2000 <br /> SUBJECT: Review of Soil and Groundwater Investigation Report and Human Health <br /> Screening Evaluation, Pombo Property, Tracy Califomia. <br /> PCA: 12045 Site: 1 01 269-1 1 <br /> Background <br /> This report details the field activities and a "screening health risk assessment" for the property lo- <br /> cated at 1755 West 11ti' Street in San Joaquin County, near the City of Tracy. Chevron's former <br /> Old Valley Pipeline was located in a right-of-way along the northern edge of the site adjacent to the <br /> Union (former Southern Pacific railroad alignment. The former pipeline transported heavy petro- <br /> leum products (crude and fuel oil) from Bakersfield to Richmond, California, from the early 1900s to <br /> the 1950s. The property is located adjacent to the former Old Valley Pipeline that had numerous <br /> known petroleum hydrocarbon releases. This investigation was designed to assess the lateral and <br /> vertical extent of petroleum hydrocarbon-affected soil along the historic right-of-way, to evaluate <br /> groundwater quality, and tc evalL3te hurnar he2!th risks %CSed by the reSiriu2l �ctrnlo`rr+n h�.irn_ <br /> carbons in the soil. <br /> In mid 1999, Earth Systems Consultants advanced four soil borings along the northern property <br /> boundary of the site. Petroleum hydrocarbon-affected soil was observed in two of the four borings. <br /> Subsequently, it was determined that a former Mohawk Service station was located on the prop- <br /> erty. As follow-on, Geomatrix Consultants performed an additional subsurface investigation to fur- <br /> ther characterize the lateral and vertical extent of the release. Field activities included the ad- <br /> vancement of 15 soil borings and the collection of soil and grab groundwater samples from se- <br /> lected borings. Environmental samples were analyzed for TPH gas, TPH diesel, TPH crude using <br /> USEPA Method 8015M, BTEX and MTBE using USEPA Method 82606, and PAHs using USEPA <br /> Method 8270 SIM (selective ion mode). Friedman and Bruya, Inc. of Seattle Washington, a Cali- <br /> fomia-certified laboratory analyzed soil and grab groundwater samples for petroleum-related hy- <br /> drocarbons. Forensic evaluation of the soil samples indicated that the petroleum hydrocarbons <br /> present in the soil likely represent degraded crude oil and aged gasoline. <br /> California Environmental Protection Agency <br /> (2) Printed on Recycled Paper <br />