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San Joaquin County Public Health Services <br /> Environmental Health Division <br /> November 4, 1999 <br /> Page 2 <br /> TPH-D, BTEX, or MTBE constituents. Based on these results, the UST excavation cavity was <br /> backfilled by Bowen Construction-Engineering using both clean imported fill and soils from <br /> Stockpiles A and C. <br /> It is our understanding that Bowen Construction-Engineering conducted additional overexcavation <br /> of the fuel dispenser area in August 1999. According to Mr.Merlin Bowen of Bowen Construction- <br /> Engineering,this overexcavation was extended to a depth of about 14 feet below surface grade,and <br /> field evidence indicated that all fuel-impacted soils had been removed. No groundwater was <br /> encountered in the excavation cavity. The fuel dispenser overexcavation cavity was backfilled with <br /> clean sand and road base in early October 1999. <br /> Workplan Elements <br /> It is our understanding that additional sampling will be required to verify the effectiveness of <br /> overexcavation of the fuel dispenser area. Thus,we propose to drill and sample two soil borings in <br /> the former fuel dispenser area using direct-push coring equipment. All activities will be conducted <br /> in accordance with applicable State and Federal guidelines and statutes. <br /> Prefteld Activities <br /> Prior to implementing this workplan,written approval will be obtained from San Joaquin County <br /> Public Health Services. In addition,a drilling permit for the Geoprobe borings will be obtained from <br /> San Joaquin County Public Health Services, and San Joaquin County Public Health Services will <br /> be notified at least 48 hours prior to initiating field activities. Prior to drilling,a Site Safety Plan will <br /> be prepared, and a tailgate safety meeting will be conducted with all site workers. <br /> Location of Borings and Monitoring Wells <br /> Proposed locations for the two borings are shown on )Figure 2. In order to assess possible fuel <br /> impacts to subsurface soils and groundwater,the two borings will be located immediately north and <br /> south from the former fuel dispenser overexcavation cavity. <br /> Drilling and Sampling of Soil Borings <br /> The two soil borings will be drilled to a total depth of about 25 feet by a State-licensed drilling <br /> contractor using Geoprobe hydraulically-driven soil coring equipment. This coring system allows <br /> for the retrieval of almost continuous soil cores,which are contained in a clear plastic acetate tube, <br /> nested inside a stainless steel core barrel. After the core barrel is brought to the surface and exposed, <br /> the core will be examined,logged,and field screened for hydrocarbons by a qualified scientist using <br /> sight and smell. Following completion,the seven investigative soil borings will be grouted to match <br /> existing grade using a cementlsand slurry. Soil cuttings generated during this investigation will be <br /> stored onsite in sealed DOT-approved containers. <br /> GRIBI Associates, <br />