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California Regional. Water Quality Control Board Central Valley Region Robert Schneider,Chair 0 Alan C.Lloyd,Ph.D. Arnold \.. Secretaryfor Fresno:13ranch Office Schwarzenegger Environmental 1685 E Street,Fresno,'Califomia 93706 Governor Protection (559)d45-511 b•Fax(559)445-5910 http!//www.waterboards.ca.gov/centwivalley 8 March 2005 M. Scott Mansholt ChevronTexaco Chevron Environmental Management Company P.O.Box 6012 San Ramon, CA 94583 REVIEW OF SOIL AND GROUNDWATER INVESTIGATION,POMBO PROPERTY,TRACY, SAN JOAQUIN COUNTY ChevronTexaco has conducted soil and groundwater investigations at the Pombo property, 1755 West 11th Street, in Tracy,San Joaquin County from: 1999 to 2004. The purpose was to determine the lateral and vertical extent of soil and,groundwater impacts caused by petroleum hydrocarbon leaks.from an abandoned crude oil pipeline(OldValley Pipeline, OVP)in operation from the early 1900s to the late 1950s. Currently, a City of Tracy Fire Department building, offices and parking lot covers the site. A retail �.. shopping mall is adjacent to the west and another is to the south, across West l la'Street. The former OVP easement,the Union pacific.Railroad,and the West Side Irrigation easement are adjacent to the north. Adjacent to these easements further north is residential housing. The earlier investigation was conducted by Earth Systems Consultants(ESC)with subsequent reports completed by Geomatrix Consultants(Geomatrix),and the most recent by Science Applications International Corporation(SAIL). Subsequent to the earlier investigations, a human.health risk screening evaluation(HHSE)was prepared by Geomatrix for ChevronTexaco (January 2000) and submitted to the Department of Toxic Substances Control (DTSC) for review. Following the DTSC review and follow-up comments by Geomatrix, the DTSC concurred with the HHSE f findings. The DTSC response, dated,27 April 2000 stated that the total risk falls within the acceptable range, and the petroleum constituents in soil do not pose an"unacceptable risk". Following the DTSC response and comments, additional site characterization and delineation work was conducted and an updated HHSE was prepared by Geomatrix(December 2000). The additional field investigations were evaluated(by ChevronTexaco and Geomatrix) for updating potential human health risks associated with residual petroleum hydrocarbons in soil and groundwater identified by the later work. The updated HHSE, dated 4 October 2001,was submitted to the DTSC for further review and comment. The DTSC in their 5 August 2002 memorandum to ChevronTexaco again concurred that the site development is acceptable and the risk falls within the acceptable range of 1 X 104 to 1 X 10-6. Further, the current land use(comrnercial/industrial) is acceptable provided a land use covenant(i. e., deed restriction) is applied to the site;limiting future development of the site for residential use. California Environmental Protection Agency 'Qr*Recycled.Paper