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Department of Toxic Substances Control Edwin F. Lowry,Director 1001 I Street, 25`h Floor P. O. Box 806 Winston H. Hickox Sacramento,California 95812-0806 Gray Davis Secretary for Governor Environmental Protection MEMORANDUM TO: Mr. Jerry Lile, Project Manager Site Mitigation Branch, Region 1 8810 Cal Center Drive Sacramento, California 95827-2106 FROM: David L. Berry, Ph.D. Senior Toxicologist Human and Ecological Risk Division (HERD) DATE: October 2, 2001 SUBJECT: 'Review of Updated Human Health Screening Evaluation, Ridgeway [former Bums] Property, Tracy, California PCA: 12045 Site: 101270-11 Background Per your technical services request, the Human and Ecological Risk Division (HERD) has reviewed the updated screening health risk assessment for a property located at 1881 Rustan Road in San Joaquin County, near the City of Tracy. Chevron's former Old Valley Pipeline was located in a right-of-way along the southern edge of the site adjacent to the Union (former Southern) Pacific railroad alignment. The former pipeline transported heavy petroleum products (crude and fuel oil) from Bakersfield to Richmond, California, from the early 1900s to the 1950s. The property is lo- cated adjacent to the former Old Valley Pipeline that had numerous known petroleum hydrocarbon releases. This investigation was conducted to further assess the lateral and vertical extent of pe- troleum hydrocarbon-affected soil along the historic right-of-way, to evaluate groundwater quality, and to evaluate human health risks posed by the residual petroleum hydrocarbons in the soil. T he most recent data collected in May and October of 2000 were used for the updated screening health risk assessment. In mid 1999, Earth Systems Consultants advanced six soil borings along the northern property boundary of the site. Petroleum hydrocarbon-affected soil was observed in two of the six borings. As follow-on, Geomatrix Consultants performed an additional subsurface investigation to further characterize the lateral and vertical extent of the release. Field activities included the advancement of 7 soil borings and the collection of soil and grab groundwater samples from selected borings. Environmental samples were analyzed for total petroleum hydrocarbons (TPH) as TPH gas, TPH diesel, TPH crude using USEPA Method 8015M, benzene, toluene, ethylbenzehe and xylenes (BTEX) and methyl-tertiary-butyl ether(MTBE) using USEPA Method 82606, and polycyclic aro- matic hydrocarbons (PAHs) using USEPA Method 8270 SIM (selective ion mode). Three addi- tional samples of groundwater and two soil were taken near a suspected leak area and down gra- dient from the former pipeline. These samples were taken in May and October 2000. Friedman California Environmental Protection Agency 9 Printed on Recycled Paper