REV14167 - Laserfiche WebLink

Home Browse Search

generated will be stored on the newly replaced or repaired liner. If it turns out that the tails are non-toxic, non-acid acid forming, they will be disposed of as outlined in the conversion application. 7. Please describe, in detail, the tailings solidification process. The Division is concerned about how the process will be conducted without jeopardizing the integrity of the tailings pond liner. Please provide a schematic drawing of this process if it will aid in describing how it will occur. First, MDI intends to cover the tailings pond liner with sand and/or gravel to prevent exposure during routine operations thus minimizing damage. Second, depending on how the characterization turns out, MDI will either mix the tailings with cement and dispose of them if they turn out to be toxic or acid producing, or simply dispose of them without mixing if they are non-toxic and non acid producing. In any event the tailings will be placed underground in the dry stope that is between the 65 level and 125 level shown on the Professional Paper 219 Plate 28, included as Appendix 4 in this response. There is no indication that the stope between the 65 level adit and the 125 level adit is wet, nor does it experience a wet dry cycle. In fact MDI's operator has been in this stope many times and claims that every time it was dry. 8. Please provide detailed information regarding the proposed disposal of the solidified tailings. Details should include; location within the workings designated for disposal, how the tails will be kept dry, and where and how the water table has been defined. As discussed in item 7 above, the tailings, regardless of their toxicity will be placed in the dry stope between the 65 level and 125 level. Plate 28 that has been submitted for reference does not indicate the location of the water table, but I am looking into this and will forward that information to you as soon as I receive it. MDI believes that the water table, is below the 175 level. As was indicated earlier, all workings above the 175 level are dry, and are not subject to repeated wet/dry cycles. This is evident through physical inspection of the stope below. 9. The Division is concerned that solidified tailings will be subjected to repeated wetting and drying cycles when stored for disposal in a "dry" stope underground. The repeated wetting and drying process could eventually break down the solidified tailings block, leaving rubble with a higher surface area available for oxidation and higher potential to produce toxic or acid mine drainage. MDI may wish to consider disposal of the tailings blocks in an area that is submerged, below the water table, at all times. This scenario may create a condition whereby oxidation would occur at a slower rate, under conditions that should not cause break down of the solidified tails block. Characterization of the solidified tailings would be necessary to evaluate this position.