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California Regional Water Quality ontrol Board <br /> Central Valley Region <br /> Robert Schneider,Chair Arnold <br /> Alan C.Lloyd,Ph.D. Schwarzenegger <br /> Secretaryfor Fresno Branch Office <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http://www.waterboards.ca.gov/centralvalley <br /> 30 March 2006 <br /> RECI <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company SAAR 3 .l [OG6 <br /> 6001 Bollinger Canyon Road <br /> Room K2066 ENVIRONMENT HEALTH <br /> San Ramon, CA 94583-2324 PERMIT/SERVICES <br /> Jim Levy <br /> Union Pacific Railroad Company <br /> 9451 Atkinson Street, Suite 100 <br /> Roseville, CA 95747 <br /> REVIEW OFDOWNGRADIENT GROUNDWATER INVESTIGA TION REPOR T, FORMER <br /> TA OC TRA CYPUMP STATION, TRACY, SAN JOA QUIN COUNTY <br /> Central Valley Regional Water Board staff has reviewed the referenced document, dated 23 March 2006 <br /> for the Chevron Old Valley Pipeline (OVP)project site, prepared for Chevron Environmental <br /> Management Company(Chevron) and Union Pacific Railroad Company by Geomatrix Consultants, Inc. <br /> (Geomatrix). The property occupies the eastern portion of the former TAOC Tracy Pump Station on <br /> Beechnut Avenue, west of Tracy Boulevard. <br /> The purpose of the investigation, in conjunction with previous investigations, was to complete borings <br /> and obtain groundwater samples to delineate the lateral extent of total petroleum hydrocarbon (TPH)- <br /> impacts downgradient of the site. Regional Board staff approved the workplan in 2004 and an <br /> addendum was approved in 2005. The report describes the installation of three temporary borings in <br /> August 2005 and January 2006 and collection of samples for laboratory analysis. <br /> According to the recent report, groundwater samples from borings SB-01 and SB-02, located <br /> approximately 350 feet downgradient(north-northwest), reported concentrations of TPH as diesel <br /> (TPHd) at 230 and 130 µg/l, respectively. Consequently, SB-04 was advanced approximately 280 feet <br /> further north of the original borings, and TPHd was non detect (ND) at that location. Polynuclear <br /> aromatic hydrocarbons (PAHs),benzene, toluene, ethylbenzene and xylenes (BTEX) and TPH as <br /> gasoline were not detected above the laboratory reporting limits in any of the samples. <br /> Hydrocarbon-impacted soil appears to be limited to within the approximate property boundaries; <br /> similarly, the highest levels of impacted groundwater onsite appear to be limited in extent, localized, and <br /> correspond to areas having elevated TPH concentrations in soil. While Regional Board staff concurs <br /> that additional characterization is not needed, removal of impacted soil containing elevated <br /> concentrations of hydrocarbons localized onsite could reduce the volume of contaminants in soil and <br /> reduce the potential of further groundwater impacts. <br /> California Environmental Protection Agency <br /> 0a Recycled Paper <br />