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SECTION 1 Introduction + This site characterization work plan has been prepared by CH2M HILL for Del Monte Foods (Del Monte), and presents the scope of work for performing additional site characterization at the Disco site in Stockton,California. i This work plan is being submitted to the Public Health Services/Environmental Health Division (PHS/EHD)of the San Joaquin County.Del Monte is complying with the PHS/EHD requirements for site characterization and remediation activities,by the Health and Safety (H&S)Code Section 25299.37 (b)(c)(6),to be eligible for reimbursement of corrective action costs from the State Water Resources Control Board Cleanup Fund (USTCF). t The field investigation documented in this work plan has been developed to further define the extent of 1,2-DCA in groundwater beneath,cross-gradient,and downgradient of the Disco property. This work plan also specifies the installation of several groundwater monitoring wells and a groundwater extraction well.The monitoring wells will provide long-terns monitoring points downgradient and cross-gradient of the site. A deep monitoring well will provide a monitoring point beneath the hydrocarbon/1,2-DCA plume. The extraction well is being installed to hydraulically control the source area of the . hydrocarbon/1,2-DCA plume. 1.1 Objectives The objectives of the field work presented in this work plan are to: • Attempt to define the vertical,cross-gradient,and downgradient extent of 1,2-DCA in groundwater beneath the site. • Install monitoring wells to provide vertical,cross-gradient and downgradient monitoring points. • Install an extraction well to attempt to hydraulically control the source area of the hydrocarbon/1,2 DCA plume. One extraction well will be initially installed to assess the hydraulic properties and maximum pumping rate of the impacted zone. This data will be used to update the existing groundwater flow model which, through performing various hydraulic capture scenarios,will optimize the number and location of any additional extraction wells necessary to obtain hydraulic capture of the source area. All information obtained during this field investigation will be used to determine the appropriate next step,with respect to additional site activities. 1.2 Work Plan Organization This work plan has been prepared following guidelines outlined in Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites,Appendix A,prepared by the Central Valley Regional Water Quality Control Board (CVRWQCB). The remainder of this work plan is divided into the following sections: • Section 2,Site Setting and Background G:IEBGIDELMONTEIPLANT_331MONITORING WELL WORK PLANIW0AKPIAN_DCA_1.DGC 2