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San Joaquin County Motor Pool Facility May 16, 2001 Additional Site Assessment Workplan Task 3B: Well Development Well development will be performed using a development rig. The wells will each be surged approximately 15 minutes. A minimum of five (5) well volumes of water will be removed from each well until the sediment is removed and baseline measurements for pH, temperature, electrical conductivity and turbidity are established or until the well purges dry. Task 3C: Groundwater Monitoring 8 Sampling Prior to collecting groundwater samples, free product thickness (if present) will be determined and the depth to groundwater will be measured in all wells to be sampled. The new and existing wells will also be properly purged using a submersible pump and dedicated tubing for each well, until the temperature, conductivity, pH and turbidity stabilize, a minimum of three (3) well volumes will be removed from each well. The groundwater level will be allowed to recover to at least 80 percent of the initial level prior to sampling. New, individually wrapped, PVC bottom-valve bailers will be used for sampling the wells. Groundwater samples will be collected by lowering the bailer approximately 1 to 2 feet below the static groundwater level. The bailer will be raised slowly in order to minimize agitation of the water sample in the bailer. Groundwater samples will be decanted from the bailers into laboratory-supplied glass containers. The samples will be labeled and placed into an ice-chilled cooler. Care will be taken to insure no air bubbles are trapped in the containers. The collected samples will be transported to a State-certified laboratory for analyses under proper chain-of-custody protocol. Task 3D: Well Survey Following the installation of the groundwater monitoring wells, the ground surface and casing tops for all new and existing wells will be surveyed to a common datum at each location. Differential leveling of the locations (0.01-foot accuracy) to mean sea level (msl) shall be included in the survey. If no benchmark has been identified within two (2) blocks of the Site a temporary benchmark will be used. Surveying services will be provided by a State-licensed surveyor. Task 4: Laboratory Analyses Soil and groundwater samples will be submitted to a State Certified on-Site mobile laboratory for immediate analysis. The soil and groundwater samples will be analyzed for Petroleum Hydrocarbons as Diesel (TPHd) and TPH-G using EPA Method No. M8015 and for BTEX, MTBE, tert-Butanol (TBA), Di-Isopropyl Ether (DIPE), Ethyl-tert-Butyl Ether(ETBE), and tert-Amyl Methyl Ether(TAME) using EPA Method No. 82608. Task 5: Report Preparation Upon completion of the field work a report will be prepared by TEM. The report will summarize field activities and will include soil boring logs, site maps showing the boring locations, figures illustrating the vertical and lateral extent of soil and groundwater impacted by fuel hydrocarbons, tables summarizing soil and ground- water analytical data, conclusions based on generated data, recommendations for further assessment work, if necessary. The report will also discuss potential soil and ground-water remedial alternatives based on field observations and analytical results including potential locations and design parameters for groundwater remediation and monitoring wells. Task 6: Quarterly Groundwater Monitoring Upon completion of the investigation TEM will initiate a quarterly groundwater monitoring program at the Site. The new and existing wells will be incorporated into the program. Page 4 of 5