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SOIL AND GROUNDWATER INVESTIGATION REPORT GEOMATRIX <br /> 35275 Welty Road -- APN 255-180-09 <br /> Vernalis, California <br /> 1.0 INTRODUCTION <br /> This report presents results of field activities performed by Geomatrix Consultants, Inc. <br /> (Geornatrix), on behalf of Chevron Environmental Management Company (Chevron), at the <br /> 35275 Welty Road site (San Joaquin County Assessors Parcel Number 255-180-09) in <br /> Vernalis, California (the site; Figure 1). Field activities included the advancement of seven soil <br /> borings for the collection of soil and groundwater samples and sampling of one groundwater <br /> monitoring well. This work was performed in accordance with Geomatrix's June 12, 1999 <br /> 1 work plan submitted to the California Regional Water Quality Control Board, Central Valley <br /> Region (RWQCB); the work plan was approved by the RWQCB in its July 13, 1999 letter to <br /> Chevron. The purpose of the investigation was to assess the vertical and lateral extent of <br /> petroleum hydrocarbon-affected soil and to assess whether residual petroleum present in the <br /> site subsurface provides a source of dissolved petroleum constituents to groundwater. At the <br /> request of the RWQCB, this investigation also evaluated the presence of trichloroethene (TCE) <br /> in site soil. Background information on the site, a summary of the activities performed, the <br /> results obtained, and our conclusions are presented below. <br /> 2.0 BACKGROUND <br /> Chevron's former Old Valley Pipeline (OVP)was located in a right-of-way parallel to the <br /> railroad tracks along the northeastern edge of the site. The former OVP transported heavy <br /> petroleum (crude oil) from Bakersfield to Richmond, California, from the early 1900s to the <br /> mid-1930s. <br /> 1 <br /> Soil and groundwater investigations have been conducted at the site by four different <br /> 1 consulting firms since 1995. During this period, multiple soil borings were advanced and four <br /> groundwater monitoring wells (MW-1, MW-2, MW-3, and MW-4) were installed at the site to <br /> depths of approximately 40 feet below ground surface (bgs) (Figure 2). <br /> Results of the investigations indicated the presence of petroleum hydrocarbons, TCE, and <br /> 1,1,1-trichloroethane (1,1,1-TCA) in site soil, and petroleum hydrocarbons and cis-1,2- <br /> dichloroethene (cis-1,2-DCE) in groundwater. Historical soil and groundwater analytical <br /> 1:1D0C_SAFE\5000S1538MS01L GW RPT.DOC 1 <br />