SITE INFORMATION AND CORRESPONDENCE

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CHEVRON PIPELINE EASEMENT ENVIRONMENTAL ASSESSMENT REPORT 1.0 INTRODUCTION This report provides the results of a soil and groundwater investigation into the possible presence of residual petroleum hydrocarbons in soil and groundwater related to an historic Chevron underground crude oil pipeline located on the southwest side of Byron Road(site), northwest of the City of Tracy, San Joaquin County, California(Figures 1 and 2, Appendix A). Soil and groundwater investigation activities were conducted at the site between June 6 and 28, and on July 24 and 25, 2001. Condor Earth Technologies, Inc. (Condor) prepared this report at the request of Mr. Eric Teed-Bose of Trimark Communities (Trimark). - Initially, the purpose of the work was to investigate the possible presence of petroleum hydrocarbons in _ soil related to the historic Chevron crude oil pipeline along Byron Road between the Alameda County line and Wicklund Road, a distance of approximately 14,400 feet. Subsequent sampling was conducted to evaluate the impact of detected petroleum hydrocarbons on construction. This report includes a discussion of the project background, a description of the fieldwork conducted at the site, the laboratory analytical results, maps with trench excavation and direct push (Geoprobe) soil boring locations, and a discussion of the results. A vicinity map and location maps are located in Appendix A. Trench and soil boring geological logs are located in Appendix B. Analytical data spreadsheets are located in Appendix C. Copies of laboratory analytical reports and chain-of-custody forms are in Appendix D, contained in Volume II. All work conducted by Condor was performed under the supervision of a Professional Engineer. 2.0 PROJECT BACKGROUND W- Between the early 1900s and the early 1960s, Standard Oil Company, later Chevron Pipe Line Company (Chevron), installed and operated an underground pipeline to transport crude oil, and later bunker oil, between Bakersfield and Richmond. Standard Oil Company obtained easements in 1902 and 1958 for a strip of land ten feet wide, parallel and adjacent to the southwestern side of Byron Road. This pipeline was located approximately three feet below ground surface (bgs) on the southwestern side of Byron Road. It is believed the pipeline was located less than 10 feet from the current pavement edge and 23 to 25 feet from the current road centerline. The exact location of the pipeline is unknown. The historic pipeline was abandoned and possibly removed after a pipeline was installed on the northeastern side of Byron Road in 1964. There is reason to believe that segments of the pipeline were never removed, as documents detailing the removal are missing. San Joaquin County widened Byron Road by 20 feet to the southwest in 1964. Petroleum hydrocarbons were reportedly observed during a geotechnical investigation along the northeastern side of Byron Road in September 1991 at a location approximately three miles northwest of the Mountain House Community (see Figure 1, Appendix A). Further investigation of the site included the installation of excavation pits, groundwater monitoring wells, and soil borings. Total petroleum hydrocarbons were reported at concentrations ranging from 1 to 9,500 milligrams per kilogram (mg/kg) in 28 of the 53 soil samples collected between 1991 and 1997. During the course of the investigation, Geomatrix Consultants (Geomatrix) determined that contaminated soil occurred between 6 and 16 feet bgs. Based on a health risk screening evaluation using Preliminary Endangerment Assessment A CONDOR