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r s <br /> 04% Californi Regional Water Quality Con rol Board <br /> Central Valley Region <br /> Karl E. Longley,ScD,PE,Chair <br /> Linda S.Adams Arnold <br /> Secretaryfor Fresno Branch Office Arnold <br /> Environrnenlal 1685 E Street,Fresno,California 93706 /� • Governor <br /> Proleclion (559)445-5116•Pax(559)445.5910 <br /> http://www.waterboards.ca,gov/centralvalley <br /> 14 June 2007 <br /> %Srx <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> Room K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW - ENVIRONMENTAL RISK EVALUATION — MOUNTAIN HOUSE DEVELOPMENT <br /> SITE #1, BYRON ROAD, MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced document, dated 15 May 2007 for <br /> the Chevron Old Valley Pipeline (OVP)/Tidewater Associated Oil Company (TAOC) project <br /> site, northwest of Tracy, CA. The report was prepared for Chevron by Science Applications <br /> International Corporation (SAIC) in response to a Regional Water Board request for <br /> clarification regarding conflicting analytical data submitted in SAIC's 16 January 2007 <br /> Environmental Risk Evaluation for the site. <br /> The project is located within an approximately 300-foot long section of the former OVP right- <br /> of-way adjacent to Byron Road near Mountain House Creek, extending generally northwest - <br /> southeast. Other active pipelines present within the former OVP right-of-way and along Byron <br /> Road convey refined petroleum product to refineries in the Richmond area. <br /> Analytical data presented in the Environmental Risk Evaluation reported elevated <br /> concentrations of total petroleum hydrocarbons as diesel (TPHd) from 1,200 micrograms per <br /> liter (lag/1) to 4,200,000 pgll present in groundwater. Additionally, TPH as gasoline (TPHg) <br /> values up to 6,400 pg/I generally correspond to samples having elevated TPHd. <br /> Benzene, with one exception of 0.1 pgll, was not detected; toluene, ethylbenzene, and xylenes <br /> (BTEX) reported concentrations at or slightly above the method detection limits. BTEX <br /> compounds are not commonly detected at TAOC or OVP sites. However, BTEX compounds <br /> are significant constituents in refined petroleum products conveyed in the nearby refined <br /> product pipelines. The absence of BTEX compounds suggests that the nearby refined- <br /> product pipelines are not leaking. <br /> Chevron Energy Technology Company (ETC) and Chevron's contract analytical laboratory <br /> staff evaluated chromatograms for a portion of the sample results in question. Their review <br /> concluded that analytical methods used could not alone definitively identify a specific <br /> petroleum hydrocarbon such as crude oil, diesel, or gasoline in a sample. Rather the test <br /> California Environmental Protection Agency <br /> qr Recycled Paper <br />