SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Based on the past records and since the tanks tested tight in late 1986, an estimate of the amount of product which escaped the r tanks cannot realistically be made. The inventory reconciliation records do not provide any indication of a leak. Therefore, it ) is reasonable to assume that the quantity of the leakage may not be great. 5.0 EXPLORATORY SOIL BORING AND MONITOR WELL SITING Three locations have been selected for the installation of the monitoring wells, as shown on Figure 6. The triangular orienta- tion of the wells should serve both to define a site specific ground water gradient and provide water quality information upgradient and downgradient of the former diesel and gasoline tank site. Three other locations have been selected for explor- atory soil borings, as shown on Figure 6. The soil borings are placed close in to the tank excavation area and surround it.,, This configuration should allow for the assessment of potential / lateral and vertical migration of possible contamination. 5.1 Exploratory Soil Boring Installation Three exploratory soil borings will be drilled using hollow stem auger techniques. Each boring will advanced to first ground water, with one boring continued to 40 below ground surface (BGS) to provide additional information on the subsurface geology at the site. All drill cuttings will be containerized in 55 gallons drums and held at the site until results of the soil sample l chemical analyses are obtained. Disposal of the cuttings will be — determined based on the results of the soil sample analytical results. Each boring will be sealed to within 1 foot BGS with a -5% bentonite -cement grout. The uppermost foot will be capped with concrete to provide structural support. 5.2 Monitor Well Installation I��Q As the anticipated depth to water is approximately 10 feet BGS, v the wells will be installed using hollow stem auger drilling techniques. All drill cuttings will be containerized in 55 gallon drums and held at the site until results of the soil *�I sample chemical analyses are obtained. Disposal of the cuttings will be determined based on the results of the soil sample U� nalytical results. T e well casing and screen will be constructed from nominal 4" diameter flush threaded P.V.C. pipe, with a 10 foot screened interval placed 8 feet into the uppermost saturated zone and extending 2 feet above the saturated zone. Based on previous experience in the area, a 0.010 inch slot screen size will be used. This may require modification if the grain size of the saturated formation is substantially different from the screen slot size. The gravel pack for the wells will utilize a washed, - 9 -