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• P*s EngineeringScience Inc. r several hundred feet to the east and southeast of the sewer line. Sampling will be performed at three depths at each of these probe locations. It is anticipated that concentrations of HVOCs in groundwater samples from the outer sampling locations (P-13 through P-16) will be low to ND. Samples from these locations will be delivered to the laboratory with instructions for 24-hour turn around time to provide time for decision-making prior to demobilization of the drilling subcontractor. Should higher detections occur, decisions will need to be made as to whether to sample additional holes. Prior to startup, additional sampling hole locations will be laid out, cleared, and permitted to cover this contingency. SOIL PROFILING Soil probes will be advanced using a truck-mounted hydraulic cone penetrometer test (CPT) rig. The CPT rig will be equipped with an instrumented piezocone to provide an electronic borehole log for lithologic interpretation. Piezocone measurements will be performed in accordance with ASTM D3441 on at least 4 of the 7 probes. The parameters of cone bearing (Qc), sleeve friction (Fs), and pore water pressure (U) will be recorded and subsurface materials will be interpreted and correlated to soils in the logs of nearby CPT and rotary auger borings that were drilled and sampled in previous phases of work. The piezocone measurements will be used to identify key horizons such as the interfaces between clay and silty sand layers. The instrumented CPT probes will be continued to an approximate depth of 110 feet. Probe penetration can occasionally be stopped by dense or cemented layers as occurred in the Phase II investigation off-site CPT location P-7. This hole was discontinued at a depth of 43 feet before reaching groundwater because resistance exceeded the capacity of the rig and because an insufficient number of alternate drill locations had been cleared. In answer to this potential problem, a CPT truck with a ballast weight of 20 tons will used to give maximum thrust. Also, various alternate locations will be cleared, especially where utility corridors are anticipated. GROUNDWATER SAMPLING WITH CPT RIG Two or three groundwater samples will be collected from each of the seven CPT probe holes using a HydropunchT' or equivalent downhole sampling device. A total of 18 samples, plus one field duplicate per day of sampling, are proposed (Table 1). Samples will be collected from depth horizons where water flows into the hole most freely. From previous site experience it is expected that sampling will be in the following depth ranges 1) shallow: 55- 65 ft, 2) mid-range: 70 to 76 ft, and 3) deep: 100 to 105 ft. All groundwater samples will be analyzed for halogenated volatile organic compounds (HVOCs). SAMPLE ANALYTICAL METHODS AND QUALITY CONTROL Groundwater samples collected with CPT equipment will be analyzed only for HVOCs by EPA Method SW8010. In four 1997 quarterly rounds of groundwater monitoring there were 0997\09072\wks2add 12-18-97 3-4