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1 <br /> WORKPLAN FOR LIMITED <br /> SOIL AND GROUNDWATER INVESTIGATION <br /> SUNNYSfDE PRODUCE, THORNTON, CALIFORNIA <br /> I INTRODUCTION <br /> Geotechnical Research and Development (GRD) has been retained to develop a workplan for a <br /> hnuted soil and groundwater investigation at the Sunnyside Produce Truck Stop in Thornton, <br /> California Previous work at the site has identified diesel and gasoline environmental impacts to soil <br /> and groundwater apparently as a result of operation of underground storage tank systems The <br /> purpose of the tasks described in this workplan are to obtain pertinent hydrogeologic information and, <br /> to the extent practical in a limited investigation, determine the nature and extent of petroleum <br /> hydrocarbons in soil and groundwater at the subject site <br /> This workplan has been developed by GRD on the basis research of the available, existing data <br /> relative to the underground storage tank(UST) closure event at the site, and prepared in accordance <br /> with guidelines in Appendix A of the Tri-Regional Staff Recommendations for Preliminary <br /> Investigation and Evaluation of Underground Tank Sites <br /> i II SITE OWNERSHIP, LOCATION AND DESCRIPTION <br /> The site is owned by the Barnyard Corporation of Stockton, California and is located at 8960 West <br /> Walnut Grove Road, Thornton, California The site(APN 001-150-29) is a truck stop, convenience <br /> store and gasoline retailing facility situated on the east side of Interstate 5 approximately 25 miles <br /> south of Sacramento, California The site is level at an elevation of approximately 10 feet above <br /> mean sea level (msl) The Mokelumne River flows northwestward approximately one-half mile <br /> northeast of the site <br /> Formerly, three USTs were located west of the north end of the convenience store building as shown <br /> on Figure I Three aboveground diesel tanks and associated dispenser islands are located southeast <br /> and west of the subject UST systems, respectively <br /> III BACKGROUND <br /> The subject USTs and associated product piping and dispensers were excavated and removed on 21 <br /> January 1999 by Oil Equipment Service (OES) of San Andreas, California Soil and groundwater <br /> samples were collected from the excavation in the presence of a representative from the San Joaquin <br /> County Public Health Services-Environmental Health Division (SJCEHD) The results of the UST <br /> removals and analytical results were documented by GRD in a letter to OES dated 10 February 1999 <br /> (Appendix B) <br /> 1� <br /> WORKPLAN FOR LIMITED SOIL AND GROUNDWATER INVESTIGATION <br /> SUNNYSIDE PRODUCE, THORNTON, CALIFORNIA PAGE 1 <br />