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r� r t. .5 Project 02260.01 November 20, I990 The temporary vacuum probes installed for the investigation were constructed of 1/2-inch diameter schedule 40 steel pipe. A point was forged on one end of each probe. A 48-inch range of 3/16-inch perforations were drilled into each probe beginning at 3 inches from the paint (Figure A). The vacuum probes were driven pneumatically into the soil to various depths (Table I). In locations where the soil was -- covered by concrete or asphalt, a I-inch diameter hole was drilled through the surface material with an electric roto-hammer to facilitate probe installation. �. After installation, a vacuum was applied to each probe or well to extract soil gas. One psi sample pressure was maintained during the analysis. Sample flow rate and instrument pressures were checked before each test. The soil gas was sampled through a 1/4-inch Teflon sample line that was connected to a stainless steel well head fitting. Use of Teflon tubing minimizes sample loss through adsorption and the possibility of distorted results from a sample line contaminated by a previous analysis. - Leak checks were performed on the sample line before the analysis. Filters were used extensively throughout the system to remove foreign material from the sample pathway. The sample line was connected to a diaphragm pump located in a mobile laboratory. The extracted soil gas was analyzed using a Beckman Model 400 Total Hydrocarbon Analyzer equipped with a Flame Ionization Detector (FID). The Beckman Model 400 was calibrated using certified standards of propane in nitrogen. The instrument was recalibrated periodically throughout the day using certified standards. Depen to groundwater was measured in all monitoring wells tested during the Soil Gas Survey using an electronic water level indicator. Performance Test The Performance Test was conducted on november 7, 1990. A portable skid containing a vacuum pump, flow meters, and vacuum gauges was used on T site. A vacuum line was connected to a temporary vacuum probe or existing groundwater monitoring well to create an extraction point. Three monitoring wells (MW-3, MW-8, and MW-I0) and two vacuum probes (P-I and P-5) were used as extraction points (Figure 1). Each extraction point was tested for 20 minutes with the exception of MW-10, which was tested for 30 minutes. Upwelling of the water table was monitored at each monitoring well extraction point during testing using a water level indicator. -- 2