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San Joaquin County Motor Poolrac��// ility May 16, 2001 Additional Site Assessment Workplan Due to the dense to very dense predominately granular fluvial deposits (silty sands to sands) encountered during the initial site assessment, TEM does not believe that electronic cone penetrometry (ECP) would be a viable option to advance the exploratory borings, or to collect representative soil/groundwater samples for laboratory analyses. Therefore, the exploratory borings will be drilled and sampled using hollow-stem auger drilling and sampling methods/techniques. At each exploratory boring soil samples for lithologic description and laboratory analyses will be collected at five-foot intervals. Upon encountering groundwater, a disposable bailer will be lowered inside the hollow-stem auger to collect a groundwater sample for laboratory analyses. A California-certified mobile laboratory will be used to analyze the soil and groundwater samples collected. Laboratory analyses of soil samples collected below groundwater(-40 to 45 feet below ground surface [bgs]) to a total depth of 60 feet bgs during the initial site assessment in borings B-1 and B-2 were found to contain elevated concentrations of TPHg, BTEX, and MTBE. To determine the vertical extent of soil contamination the proposed initial exploratory boring (13-8) east of and immediately adjacent to the former location of UST#3 as illustrated on Figure 1 will be advanced and sampled to 100 feet bgs. Phase Two Phase Two will involve evaluating the physical and analytical data generated by Phase One to locate and design groundwater remediation wells and plume monitoring wells to be installed at the Site. Ideally, the remediation wells would be installed along the axis of the delineated groundwater plume, with monitoring wells located along the flanks, up-gradient, and down-gradient relative to the groundwater plume. OBJECTIVE The objective of the additional site assessment is to: • Delineate the vertical and lateral extent of fuel hydrocarbons in the subsurface soils and groundwater beneath the Site. • Define the locations of and design parameters for groundwater remediation wells and monitoring wells to be installed at the Site. • Implement a quarterly groundwater monitoring and sampling program to include all new and existing wells at the Site. SCOPE OF WORK The scope of work that TEM has developed to meet the objectives includes the following tasks: Task 1: Health and Safety Plan Modification A health and safety plan (HSP) will be prepared for the proposed scope of work. The HSP is designed primarily to minimize exposure of TEM personnel and its subcontractors to potentially hazardous materials. The plan will be prepared under the direction of the Corporate Health and Safety Officer and will be implemented in the field by the Site Safety Officer. Task 2: Permitting and Notifications Underground Services Alert (USA) will be notified to delineate underground utilities 48 hours prior to initiating drilling activities. The San Joaquin County Public Health Services, Environmental Health Division will be notified three days before drilling commences. Page 2 of 5