SITE INFORMATION AND CORRESPONDENCE

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Mr. Howard Hold August 27, 2004 Page 3 to ensure that MW2 also represents background conditions. The data from these two shallow monitoring wells then provides greater assurance that the plume is localized beneath the ponds and has not migrated downgradient and affected the ground-water quality monitored at MW2. In the event that the ground-water quality results at MW5A indicate that there has been an impact at the new location, another background well may be required. • MW6A: Presently, there are no monitoring wells located north of and at a position close enough to the north pond to provide control on the plume estimate in this direction. A shallow zone monitoring well is planned at a location that would also be within an area considered downgradient of the ponds. Monitoring results for this location would provide an indication of the magnitude of impacts that have occurred in the vicinity of the ponds at a location further removed from the ponds than existing shallow zone wells (e.g., MW i and MW3A). A monitoring well at the revised location is also anticipated to be beneficial for further assessing corrective action measures and for inclusion in the corrective action monitoring program. • MW6B: Similar to what is described above for well MW6A, control is lacking north of the ponds and a deep zone monitoring well is proposed (e.g., this well is positioned at a location presently down gradient to cross gradient of the observed direction of ground- water flow in the deep zone). The proposed location to the north would provide additional gradient control at a location away from facility pumping and would also provide additional information to further refine the apparent limited impact of historical operations on the deep zone. Test Holes Test holes will be drilled at each of the two well locations using mud rotary drilling methods. The first test hole(at the MW613 well location) will be drilled to a depth of approximately 250 feet. The test hole borehole diameter will be 8-3/4 inches;cuttings samples will be collected at 10-foot intervals or when there is a change in lithology. Following drilling, geophysical logs will be run in the borehole for spontaneous potential and a resistivity suite (long and short normal and single point). MW6B will be constructed in the test hole. Final well designs will be based on interpretation of the geophysical log, lithologic data, and prior geologic information for the site. Following the construction of MW613, the drilling rig will move over approximately 10 feet and drill a 12-1/4-inch diameter borehole to approximately 150 feet for the construction of MW6A. Geophysical logging will not be conducted in the MW6A borehole since the logging of the MW613 borehole should provide adequate definition of subsurface conditions at this monitoring location. Following the construction and development of MW6A and MW6B, the drilling rig will move to the MW5A site. The test hole at this location will be constructed to a depth of about 150 feet. Upon reaching the target depth, a geophysical log will be conducted as described previously for the MW6B site.