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DISCO PROPERTY,STOCKTON,CALIFORNIA <br /> i <br /> Objectives <br /> The primary objectives of this workplan are to: <br /> • address the requirements by PHS for final characterization, <br /> • provide a flexible approach that allows for decisions and/or modifications to occur <br /> during implementation,and <br /> • provide investigation results for the purpose of evaluating the Disco property for <br /> closure. <br /> i <br /> Subsurface Investigation Plan <br /> i <br /> This subsurface investigation plan is organized according to the following activities: { <br /> • Activity I- Soil and Groundwater Investigation in the Former Gas-Island Area <br /> i <br /> • Activity II-Groundwater Investigation Downgradient of Former Disco Tanks <br /> • Activity III -Installation of Upgradient Monitoring Well <br /> As previously discussed,one of the objectives of this workplan is to provide flexibility for <br /> the number and locations of borings and monitoring wells. Based on the Activities <br /> described below, a total of 6 to 7 borings will be drilled,and 2 to 4 shallow (i.e.,water table) <br /> monitoring wells and 2 to 3 deep (i.e.,vertical extent) monitoring wells will be installed. All <br /> final locations for borings and monitoring wells will be determined in the field with input <br /> from PHS. <br /> Activity I - Soil and Groundwater Investigation in the Former Pump-Island Area <br /> i <br /> The objective of Activity I is to collect additional data from the former pump-island area to <br /> better understand the extent of contamination in the shallow soil above the water table and <br /> the vertical extent of contamination in the soil and groundwater. <br /> To satisfy the above objective, the following subtasks are prescribed: 1)prefield activities,2) <br /> field activities, 3) analytical chemistry and 4) Reporting. In addition,PHS recommended <br /> that Del Monte regrade the property in those areas where surface water commonly ponds. <br /> It is recommended herein to perform this regrading prior to initiating Activity I field work <br /> because the Activity I boring locations are located in one of the larger depressions. <br /> Subtask 1 Prefield Activities <br /> The following prefield activities are recommended: <br /> i <br /> • Regrading the soil in the pump-island area to minimize surface water ponding and 4 <br /> improve conditions for monitoring well completion in this area. I <br /> I <br /> 2 <br /> 4 _, <br />