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San Joaquin County Public Health Services Environmental Health Division January 14, 2000 Page 2 vicinity of the clarifier inlet on the south side of the clarifier,and three borings sited adjacent to the clarifier outlet on the north side of the clarifier. In order to assess both soil and groundwater impacts, both soil and grab groundwater samples will be collected from the borings. WORKPLAN ELEMENTS Based on the project approach summarized above, the soil boring investigation will include the following key elements. All activities will be conducted in accordance with applicable State and Federal guidelines and statutes. Prefield Activities Prior to implementing this workplan, written approval will be obtained from San Joaquin County Public Health Services. In addition,a drilling permit for the direct-push soil borings will be obtained from San Joaquin County Public Health Services, and San Joaquin County Public Health Services will be notified at least 48 hours prior to initiating field activities. Prior to drilling,a Site Safety Plan will be prepared, and a tailgate safety meeting will be conducted with all site workers. Location of Borings and Monitoring Wells Proposed locations for the eight borings are shown on Figure 2. In order to assess possible hydrocarbon releases from the clarifier, five of the borings will be located in the vicinity of the clarifier inlet at the south end of the clarifier. In addition,three borings will be located in the vicinity of the clarifier outlet at the north end of the clarifier. Drilling and Sampling of Soil Borings The eight soil borings will be drilled to a total depth of about 12 feet by a State-licensed drilling contractor using Geoprobe hydraulically-driven soil coring equipment. This coring system allows for the retrieval of almost continuous soil cores,which are contained in a clear plastic acetate tube, nested inside a stainless steel core barrel. After the core barrel is brought to the surface and exposed, the core will be examined,logged,and field screened for hydrocarbons by a qualified scientist using sight and smell. Following completion,the eight investigative soil borings will be grouted to match existing grade using a cement\sand slurry. Soil cuttings generated during this investigation will be stored onsite in sealed DOT-approved containers. Subsurface soils will be sampled at approximately four-foot intervals starting at four feet in depth. After the sample and core barrel is raised to the surface, each sample was collected as follows: (1) The filled acetate tube will be exposed for visual examination; (2) The selected sampling interval will be collected by cutting the sample and acetate plastic tubing to the desired length (typically about six inches); (3) The ends of the selected sample will be quickly wrapped with Teflon sheets or aluminum foil,capped with plastic end caps, labeled and wrapped tightly with tape; and(4)The GRIBI Associates