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16.. ..s sampling,the sampling device will be lowered to the bottom of the boring and advanced an additional 4 to 5 feet into the undisturbed portion of the aquifer. Groundwater samples will be extracted from the sampling device using a small diameter bailer and transferred to appropriate sample containers.Sample bottles to be analyzed for volatile organic compounds will be filled to overflowing so that no air bubbles are present within the bottle. All relevant information (e.g.,boring designation,volume of water extracted, time of sampling)will be recorded in a field notebook. Groundwater samples will be obtained at three discrete depths from the 5 borings installed :. around the former tank and pump area. The first sample will be collected from the depth of the water table interface (approximately 45 feet bgs).Two additional groundwater samples will be collected from approximately 110 ft bgs, and from between 130 to 150 feet bgs. The �. depth of the deepest sample will be dependent upon on the capabilities of the CPT rig. The groundwater samples will be obtained at two discrete depths from the two downgradient borings. The first sample will be obtained from the depth of water table interface,and the second sample will be collected at approximately 70 feet bgs. Because the shoulder of Highway 4 is approximately 30 feet below the elevation of the site, 70 ft bgs corresponds to a depth below the site of approximately 100 ft bgs. Monitoring data from piezometers NP-1-70', -80' and-90' indicate the maximum concentrations of petroleum hydrocarbons are detected at 80 ft bgs. Therefore, accounting for the slightly downward vertical gradient, 70 ft bgs is an appropriate depth to intercept the downgradient plume,if it exists at this location. L. All groundwater samples will be analyzed for TPH-gas, BTEX,Methyl-tert-Butyl Ether (MTBE),tert-Amyl Methyl ether(TAME),Di-isopropyl ether (DIPE),Ethyl-tert-butyl ether �- (ETBE), and tert-Butanol (TBA),in a state-certified laboratory. The groundwater sample locations, depths, analyses,and rationale, are summarized below: Groundwater Number Depth Analysis Rationale Sample Location of borings L Former Tank and 5 Water Table TPH-G/BTEX, Assess if floating Pump Area Interface Oxygenates hydrocarbon product or (45-50 ft bgs) plume present Former Tank and 5 110 ft bgs TPH-G/BTEX, Assess vertical extent of Pump Area Oxygenates hydrocarbons beneath source area Former Tank and 5 130-150 ft bgs TPH-G/BTEX, Assess vertical extent of �- Pump Area Oxygenates hydrocarbons beneath source area Downgradient 2 Water Table TPH-G/BTEX, Assess if floating (Hwy 4 shoulder) Interface Oxygenates hydrocarbon product or (15-20 ft bgs) plume present downgradient Downgradient 2 70 ft bgs TPH-G/BTEX, Assess downgradient (Hwy 4 shoulder) Oxygenates lateral extent of plume SFdCFBERNET/GROUPS/EBG/DELMoNTE/PLANT_33/woRKPLRN_CPT.Doc 7 V