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April 8 1993 • P � Job No.: EK-6032-2 Document No.: 4304-4015.WPT Exploratory Drilling, Soil gnd Groundwater Sam" fin will drill seven exploratory borings at the site after acceptance of this work plan by the San Joaquin County Public Health Services, Environmental Health Division and acquisition of the appropriate permits. Underground Service Alert will be utilized to help locate any underground utilities in the vicinity of the_drillingLocations. Two of the borings will be located on opposite sides of the derg undtieeVelitank a the Thorsen Trucking facility. One of these borings will extend to an approximate depth of 20 feet,and the other boring,on the apparent down gradient side of the tank, will extend to groundwater at an estimated depth of 25 to 30 feet. Soil samples will be collected from the borings at approximate depth intervals of 5 feet and one reconnaissance groundwater sample will be collected with a HydroPunchTM. Two additional exploratory borings will be drilled near the northern boundary of the site,adjacent to the farmer Bloom Auto Wrecking yard. One of these borings will be drilled to a depth of 10 feet and the other to groundwater(25 to 30 feet). Soil samples will be collected from the borings at approximately 5-foot depth intervals. A HydroPunchTM groundwater sample will be collected from the deeper boring. ESE also proposes to drill three borings along the southern site boundary,adjacent to another auto wrecking yard. Two of the borings will be advanced to a depth of 10 feet and the third boring will extend to groundwater. Soil samples will be collected at an approximate depth interval of 5 feet during the drilling of the borings and one HydroPunchTM groundwater sample will be collected from the deep boring. Four shallow soil samples will be collected from each of the three vacant parcels with a hand- advanced steel core sampler. An additional three shallow soil samples will be similarly collected at the Thorsen Trucking facility. The borings will be drilled with a truck-mounted drill rig utilizing hollow stem augers. The auger and other tools used in the hole will be steamed cleaned before use and between borings to minimize the possibility of cross-contamination. Relatively undisturbed soil samples will be collected at 5-foot minimum depth intervals and at major lithologic changes using a Califomia split spoon sampler with internal brass liners. As each boring is advanced to a desired sampling depth, the sampler will be lowered to the bottom of the hole and driven 18 inches ahead of the auger with a 140-pound hammer. The sampler will be removed from the hole and disassembled into its component parts. Soil from within a selected brass liner will be designated as the sample and properly preserved for transport to a state-certified laboratory. The soil in the remaining liners will be screened for volatile hydrocarbons using a portable organic vapor meter(OVM). If a positive reading is registered,the designated sample will be analyzed at the laboratory. The geologist will prepare a log of the subsurface conditions encountered during drilling and will classify the soils according to the Unified Soil Classification System. During drilling and between sampling intervals,the sampler will be scrubbed and washed with trisodium phosphate and rinsed with clean water. At completion of drilling activities,each boring will be backfilled with bentonite/cement slurry. All drill cuttings will be stockpiled on-site between layers of plastic sheeting pending disposal at an approved facility.