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• Drill a series of up to 180 closely spaced grout holes underneath either of the <br />current Electrofracs (EF1 or E173). These holes would be spaced 4-5 feet apart, <br />drilled from the adjacent mine tunnels, and directed under the Electrofrac. Their <br />average lengths will be from 70 (EF1) to 110 (EF3) feet. Figure 1 shows a 3-D <br />image of a possible geometrical configuration for both EF1 and EF3. In the image, <br />121 grout holes are shown underneath each of EF 1 and EF3. <br />Inject cement grout under pressure into the closely spaced grout holes. Pressures <br />will be kept below the known fracture pressure in the mine of 150 psi. Grout will be <br />injected into packed-off intervals in each hole. The grout is expected to fill natural <br />fracture flow paths in the vicinity of the packed-off intervals. When all the holes <br />have been grouted, together they will form a "grout curtain" or barrier to fluid flow. <br />Drill a set of up to 12 "grout integrity test holes." These holes will facilitate <br />pressure testing of the "grout curtain." Two example holes are shown in Figure 1, <br />drilled from the decline up into the "basin" formed by the grout holes. Similar <br />holes may be drilled from the north drift, the south drift, or the crosscut. They can <br />be used to test whether a water level can be held in the basin, thereby evaluating the <br />quality of the barrier. <br />In addition to the post-grouting water level tests described above, permeability testing <br />will be done on the grout holes as they are drilled and grouted. Normally, a coarse <br />network of holes is drilled and grouted, and this network is subsequently filled in with <br />additional holes. As infill grout holes are drilled, water injection into them is attempted <br />to gauge whether the previous grouting of nearby holes has formed an effective seal. <br />The construction of the grout barrier is proposed as a highly protective environmental <br />step to minimize contact with the underlying aquifer. In addition to the grout barrier, <br />hydrology studies are underway to evaluate transport of potential experimental <br />constituents to the property boundary, together with the dilution and biodegradation of <br />such constituents. <br />Technical Revision Submittal