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San Joaquin County of Public Works January 15, 1999 Workplan for Site Assessment Task 5: Well Survey Following the installation of the groundwater monitoring wells, the ground surface and casing tops for all 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 may be provided by Tait and Associates, a State- licensed surveyor. Task 6: Disposal of Solid/Liquid Waste Soils and decontamination and development water generated during the well installation activities will be contained in DOT-approved 55-gallon drums. Following receipt of the analytical results, TEM, on behalf of the County of San Joaquin, will arrange for the disposal of all solid and liquid waste generated during the well installation activities. Task 7: Groundwater Monitoring & 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 wells will also be properly purged until the temperature, conductivity, pH and turbidity stabilize. 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 3 to 5 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 8: Laboratory Analyses Up to ten (10) soil samples will be collected from each of the borings and submitted to a laboratory for analyses. The soil samples will be analyzed for the gasoline fraction of total petroleum hydrocarbons (TPH-G) or (TPH-D) using California OHS method for TPH (8015 modified). Benzene, toluene, ethylbenzene, and total xylenes (BTEX) and MTBE will be analyzed via EPA Method No. 8020. Groundwater samples will also be analyzed for TPH-G, BTEX and MTBE in accordance with the CDHS Method for TPH (8015 modified), and EPA Method No. 8020, respectively. If MTBE is detected, it will be quantified using EPA Method No. 8260. 5