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Cjeo(va(Tecknics I=. Page 2 C&B Equipment Additional Site Characterization Work Plan Project No. 336.2 July 15, 1996 j 2.0 LATERAL DEFINITION OF THE GROUNDWATER PLUME r The following work is proposed to define the lateral extent of the groundwater plume at C & Cj B Equipment. Except where noted, all drilling and sampling will be conducted as per the Geological Technics Inc. June 15, 1996 Monitoring Well Installation and Groundwater Monitoring Work Plan. 1 2.1 Soil Boring and Discrete Water Sampling To further investigate the extent of gasoline range petroleum hydrocarbons in the groundwater environment, Geological Technics Inc. proposes to install four exploratory borings surrounding the point of release. The borings will be advanced using continuous flight hollow stem augers (HSA). Because the shallow water bearing zone this site has distinct zones which the existing groundwater monitoring wells are screened across, we propose to additionally collect discrete groundwater samples from each representative lithologic unit. Reference the Geologic Cross Section in Figure 5 for illustration of geologic units and sample location. The HSA boreholes will be advanced to the capillary fringe and a capillary fringe soil sample C# will be collected. Once the capillary fringe sample has been collected, an appropriate groundwater sampling tool will be advanced into the saturated zone. Groundwater samples will be collected as outlined below in Section 2.2. 2.2 SimulProbe Groundwater Sampling Procedure C We believe that the SimulProbe sampling tool is the appropriate tool for the task given its design. The SimulProbe allows a soil sample to be collected at the exact interval from which the water sample is collected thus providing correlative information for geology and for the sorbed portion of the contaminated zone. Furthermore the design of the SimulProbe reduces the possibility of cross contamination from shallower borehole waters. After the SimulProbe groundwater sampling tool is advanced into the saturated zone the tool is retracted to expose the screen. The sample collection chamber is allowed to fill under ambient hydrostatic pressure. Once full the chamber is sealed with an pneumatically actuated (N, gas) solenoid valve and the apparatus is brought to the surface. The sample chamber is carefully emptied using a bottom emptying device thus reducing the possibility of sample C agitation and volatilization. Once the sample container (40 ml VOA) is filled and capped, the bottle will be inverted, tapped, and checked for head space bubbles. The sample container is identified and labeled with a unique designation, inserted into foam holders and C+ placed in an ice chest cooled to 4°C for transport to the laboratory. All sampling equipment is decontaminated using a steam cleaner before and between uses. The effectiveness of the decontamination procedure is ensured by using the following quality !•' control measures: Disposable gloves will be used while collecting all samples and will be changed with • each sampling event.