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California0egional Water Quality Cool Board <br /> Central Valley Region <br /> ion °+ <br /> , <br /> Karl E. Longley,ScD,PE,Chair r <br /> Linda S.Adams Arnold <br /> Secretary for Fresno Branch Office Schwarcenegger <br /> Environmental 1685 E Street,Fresno,California 93706 <br /> 559 445-5116•Fax 559 Governor <br /> Protection t � � �445-5910 <br /> http://www.waterboards.ca.gov/ccntralvalley <br /> 4 May 2007 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Ballinger Canyon Road <br /> Room K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW OF ENVIRONMENTAL RISK EVALUATION— MOUNTAIN HOUSE <br /> DEVELOPMENT SITE #2, BYRON ROAD, MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced report, dated 6 February 2007 for the <br /> Chevron Old Valley Pipeline (OVP)/Tidewater Associated Oil Company (TAOC) project site, <br /> northwest of Tracy. The OVP and TAOC lines transported only heated crude oil from Kern <br /> County oil fields to refineries in the Richmond area until the late 1960's. In the early 1940's, <br /> the OVP reportedly was intermittently used to transport Bunker C fuel oil from the Richmond <br /> refineries to railroad hubs in Tracy. The lines were abandoned in the 1970's. <br /> The site is within an approximately 250-foot long section of the former pipeline right-of-way <br /> adjacent to Byron Road near Mountain House Creek, extending generally northwest - <br /> southeast. Mountain House Site #2 is adjacent, immediately northwest of Site #1. Science <br /> Applications International Corporation (SAIC) prepared the report for Chevron. <br /> Additionally, Regional Water Board staff reviewed the 15 May 2005 soil and groundwater <br /> investigation report completed for Chevron by SAIC during April 2004. SAIC's characterization <br /> report addressed site conditions as a follow-up to investigations previously conducted by <br /> Condor Earth Technologies in 2001, the only other site investigation conducted. <br /> Soil <br /> SAIC's 2004 investigation reported total petroleum hydrocarbon as crude oil (TPHc) at <br /> concentrations from 530 to 1,400 mg/kg in boring (MH2-6) at depths from two to 27-feet, the <br /> maximum depth sampled. The other eight borings reported TPHc at concentrations from not <br /> detected (ND) for the majority of the samples to 98 mg/kg at 20-feet in boring MH2-1. Nearby <br /> Condor boring GP-175 reported 12,000 mg/kg at 20-feet, the maximum TPHc concentration <br /> reported at Mountain House Site #2. <br /> Crude oil thickness in borings was reported at depths ranging from 19 to 36 feet; affected soil <br /> up to 15-feet in thickness was observed. BTEX (benzene, toluene, ethylbenzene and xylenes) <br /> Calfornia Environmental Protection Agency <br /> cl Recycled Paper <br />