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Mr. Ed. Baker April 18, 2003 Page 4 Q7.1: Provide details on the number of subsidence monitoring wells (SMGV) that will be installed as the number of cavities increases. At minimum, there should be one .SMW per two cavities. A: We propose that one SMW be installed per two cavities. We may install another SMW with the development of the next cavern and delay installation of additional SMW's beyond these two wells if no deformation is detected, or if the TDR cable fails prematurely and indicates a false reading of rock movement. Q7.2: How will the SMW's be constructed? A: The SMW will be instrumented with four TDR cables. After setting the surface casing, an 8-inch borehole will be drilled to a depth corresponding to 45 ft above the Dissolution Surface, to a depth of approximately 1833 ft. Depths to stratigraphic contacts will be picked by geophysical borehole logging. Figure 1 shows the proposed configuration for the first SMW. The borehole wall will be flushed to remove any material that might be caked on the wall, or might compromise the bonding of the cement grout to the rock wall. Following logging, the TDR cables will be fixed to 80 ft of PVC pipe that will be attached to flush-coupled drill steel. The four TDR cables, each with end caps, and crimps, at 50-foot spacings above the end of cable, will be strapped to the PVC pipe and inserted down the borehole by advancing the PVC/drill steel to the pre-determined depth. The borehole will be grouted to a level corresponding to 100 ft above the LS-R6 contact through the drill steel and PVC pipe. The grout used will be a high-early cement with 5% to 7% expansive agent If sulphate concentrations are greater than 150 ppm, then a sulphate resistant cement, Type II, should be used. The PVC pipe will then be disconnected from the drill string by reverse rotation and the drill string raised to 115 ft above the LS-R6 contact. After waiting on cement for 24 hours, the remainder of the borehole will be grouted using the drill string as a tremie line. The drill string will be withdrawn as the cement is placed to within 2 ft of the surface. Type I or II cement can be used with a 2% expansive agent, depending on the sulphate content of the groundwater. The surface completion will be such that the cables have a security cover for protection from vandals and moisture. Q7.3: How will the SMW's be tested to assure that the TDR cables and associated monitoring systems are functioning? A: The TDR cables will be tested on the spool prior to installation, again after deployment in the borehole but prior to grouting, and again once the grout has set in the borehole. The baseline reading will occur after the grout has had time to cure, typically between 14 and 28 days. After the baseline reading, the TDR cables will be monitored at a frequency of once per month. Agapito Associates, Inc.