2007-11-20_REVISION - M1982015 (14)

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8.2 Air-Sparge Pilot Test Results The air-sparge (AS) pilot test was performed by attaching an air compressor to the AS pilot test well AS-1 and applying a pressure at increments for 15 minutes. The same monitoring wells used for the SVE pilot test were measured for pressure. The results of the test are presented below. AS Pilot Test Results Pressure in AS-1 (psig) Air Flow (SCFM) SVE-1 (10 ft) MW-1R (20 ft) MW-17 (30 ft) MW-6R (50 ft) 5 2.0 0.04 0.06 0.04 0.04 10 5.0 0.12 0.10 0.03 0.10 15 6.0 0.17 0.12 0.10 0.12 20 6.5 0.17 0.18 0.10 0.12 Based on the field data, pressure breakthrough occurred at 5 psig and 2.0 SUM. Pressure in the outlying wells and air flow peaked at about 15 psig. Pilot test well SVE-1 was monitored for VOCs using a PID. A maximum measurement of 1,070 ppm was recorded. The test was deemed successful and the testing was stopped. 9.0 Additional Characterization and Monitoring Schedule Since completion of the slurry wall, there are two hydrologic regimes each containing BTEX contamination. Groundwater elevations and flow are still changing and will continue to do so particularly on the north side of the wall. 9.1 New Wells North of the Slurry Wall Based on the groundwater sampling data from the new well installations, the extent of the dissolved phase plume is not fully delineated particularly to the north of the slurry wall. Wells are also needed to delineate the eastern and western limits of the plume. E-21 recommends installing seven new wells to determine the northern, eastern and western limit of the dissolved phase plume. The new well locations are shown on Figure 8. The wells will be constructed of 2-inch diameter Schedule 40 PVC wells materials in similar fashion to wells already onsite. 9.2 New Wells South of the Slurry Wall The extent of the dissolved phase plume is not as widespread and is generally confined to the area around MW-18 near the release point. E-21 will attempt to install two to three new wells generally to the south and east of this well. However, this area is not easily accessible due to difficult terrain and thick riparian vegetation. Monitoring wells may need to be installed without the aid of truck-mounted drilling rigs. The river bank is filled with large amounts of concrete rubble and the river bottom contains mostly gravel and large cobbles making manual installation of wells difficult as well. If new wells can be installed, they will likely be relatively shallow and may not contain an ideal sand filter pack. Although, they should suffice for groundwater monitoring purposes. 11