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i l pack is seated with 2 feet of bentonite. Overlying the bentonite seal is a neat-cement grout that extends to the surface. Groundwater sampled from SB-2, SB-3, and SB-7 contained high concentrations of TPH(g) and BTEX. To establish a plume boundary -in the westerly direction, SB-6 was drilled 120 feet west of SB-2. To establish an easterly plume boundary, SB-8 was drilled 100 feet east of SB-7. Analytical results revealed that SB-6 and SB4 groundwater did not contain 1 detectable gasoline constituents. SB-6 and SB-8 were converted to 2-inch-diameter shallow monitoring wells MW-DIS-10 'and MW-DIS-9, respectively. The monitoring well construction details are presented in Appendix B. } Aquifer Pump Testing CH2M HILL performed pumping tests on monitoring wells MW-DIS-8S and MW-DIS-8D on February 16 and 17, 1995. The tests were performed to determine the hydraulic properties of the aquifer underlying the affected portion of the Disco site. The pumping tests were designed to calculate the hydraulic conductivity, transmissivity, and storativity of the uppermost and the second water-bearing zones, referred to as the A and B Zones. Pump Testing Procedures and Results Pump tests were performed with a variable-speed submersible well pump, and drawdown in ( each well was recorded with Hermit 1000 data loggers. MW-DIS-8D Pump Test The first pump test was conducted using MW-DIS-8D as the pumping well. Drawdown was logged in adjacent wells MW-DIS-2,_MW. SCIS, MW-DIS-8S, and MW-DIS-10, each � screened between 65 feet and 85 feet bgs (A Zone), and in MW-DIS-7D, which is screened( ; between125feet and 145 feet bgs (B Zone). Figure 3-1 shows the relationship of the observation wells in plan view relative to the pumping well. MW-DIS-8D was pumped for 100 minutes ata constant discharge pumping rate of 1.2 gpm. After the first 100 minutes, the pumping rate was increased to 2.1 gpm to increase the stress on the aquifer. At this higher pumping rate, the test ran 73 minutes before the pump turned off due to overheating. Time drawdown data for all observation wells are presented in Appendix C. Figure 3-2 is a hydrograph showing the water level response in the observation wells during this pump test. The hydrographs reveal that the observation well MW-DIS-7D exhibited approximately 0.5 feet 'of drawdown during this test. The drawdown was insignificant in the other observation wells. MW-DIS-8S Pump Test MW-DIS-8S was pumped on February 17, 1995, using three separate pumping rates. The first of these three tests was performed at a pumping rate of 5 gpm. After 14 minutes, water levels in the pumping well dropped below the pressure transducer and the test was halted. SF010030982.DOC 3-4