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i Work Plan for Additional Assessment ARCO Facility No.2186 Stockton._California Page 3 only able locate one water well. Delta has been unable to reach a representative of the church at this time to gather further information regarding their well(s). Based on the information presented in the Oak Park West Well log(installation date and construction r details) the well is likely that which was previously identified in the survey conducted by Pinnacle. However, the location of the well is not the same. Oak Park West Well is located closer to the ARCO site and further to the west than reported in the Pinnacle survey. Based on the locations of the two wells in Oak Park, Delta is proposing to install two groundwater monitoring wells,between the ARCO site and each of the Oak Park wells. .Figure 2 presents the locations of the Oak Park wells and the proposed groundwater monitoring wells. SCOPE OF WORK The primary objectives associated with the proposed scope of work are: • Assess the extent of petroleum hydrocarbon impacted groundwater and evaluate possible offsite migration, + Evaluate the hydrocarbon impact of the first encountered groundwater, f • Evaluate the flow direction and gradient of the first encountered groundwater, arid • Identify an appropriate remediation alternative based the results of a feasibility study. To accomplish these objectives,the following activities are being proposed. • Install one groundwater monitoring well downgradient (northeast) of the site and install two monitoring wells offsite between the site and the two nearest water supply wells. • Collect soil and groundwater grab samples (via hydropunch) from the three soil borings for laboratory analyses. • Develop and sample the groundwater monitoring wells. • Sample groundwater in the shallow vapor extraction wells (VW-I through VW-3). • Survey the elevation and horizontal coordinates of the top of casing of each new monitoring well and the existing vapor extraction wells. • Conduct a 12 hour vapor extraction feasibility test using the existing vapor extraction wells. The scope of work has been subdivided into tasks 1 through 5. All geologic work will be under the direct supervision of a State of California .Registered Geologist and will be conducted in accordance with standards established by the Tri-Regional Board Guidelines for Hydrocarbon Site Assessment and Remediation (RWQCB 1991). Appendix B, Field Procedures and Practices and Appendix C, Sampling and Analysis Procedures present detailed procedures associated with the proposed activities. Task 1: Prefield Activities Following approval of the work plan by PHS/EHD,the following activities will be completed: • Prepare a Site-specific Health and Safety Plan,