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California Regional Water Quality Control Board <br /> QW; Central Valley Region <br /> Robert Schneider,Chair <br /> Alan C.Lloyd,Ph.D. Arnold <br /> Secretaryfor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 fi Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http://www.waterboards.ca.gov/centralvalley <br /> 8 March 2005 nECE� V E LFLI:':'), <br /> PEAR 1 0 7005 <br /> M. Scott Mansholt <br /> ENVIRONMENT HEALTH,H <br /> PERM IT/SERVICES <br /> Chevron Environmental Management Company <br /> P.O. Box 6012 <br /> San Ramon, CA 94583 <br /> REVIEW OF SOIL AND GROUNDWATER INVESTIGATION—MOUNTAIN HOUSE SITE #1, <br /> TRACY, SAN JOAQUIN COUNTY <br /> We have reviewed the Soil and Groundwater Investigation Report, Mountain House Site #1, Tracy, <br /> dated 24 January 2005 for the ChevronTexaco Old Valley Pipeline (OVP)project site, northwest of <br /> Tracy, CA. The site is located within an approximately 300-foot long section of the former pipeline <br /> right-of-way adjacent to Byron Road near Mountain House Creek, extending somewhat northwest- <br /> northeast. The OVP transported heated crude oil and Bunker C from Kern County oil fields to refineries <br /> in the Richmond area until the 1970's. <br /> Additionally, we reviewed a 26 November 2001 soil and groundwater investigation completed for <br /> ChevronTexaco by Condor Earth Technologies. The Condor investigation identified different locations <br /> along the former OVP;including the subject site that had been impacted by leaks. <br /> Currently, installation of a replacement bridge for Byron Road over Mountain House Creek is being <br /> constructed at the site, where the Mountain House Creek and Streambed Alteration project is underway. <br /> Consequently, we reviewed various project reports associated with construction dewatering wells needed <br /> during the new bridge construction and subsequent treatment of extracted groundwater. The <br /> construction activities and dewatering wells are at the approximate center of the Mountain House Site# <br /> 1 soil and groundwater investigation project addressed in the January 2005 report. <br /> The report describes the installation of 30 temporary borings and collection of soil and groundwater <br /> samples for laboratory analysis. The purpose of the investigation was to characterize the lateral and <br /> vertical extent of total petroleum hydrocarbon (TPH)-impacted soil and groundwater at this site. <br /> 1n addition to analysis of samples for vertical and lateral delineation purposes, soil and groundwater <br /> samples were analyzed for the TPH constituents of concern(TPH as diesel [TPH-d], polynuclear <br /> aromatic hydrocarbons [PAHs], and BTEX, i.e. benzene, toluene, ethylbenzene, and xylenes) to support <br /> a future Human Health Screening Evaluation (HHSE); method detection limits, consistent with values <br /> required for conducting a human health risk assessment,were used. The samples for HHSE purposes <br /> were obtained from a depth of two feet and six to ten feet; lateral and vertical characterization samples <br /> were obtained at depths of up to 48 feet. <br /> California Environmental Protection Agency <br /> Co Recycled Paper <br />