Panel Report

6.1 Mining Method

Cogema proposes to use a non-entry mining method that was developed at the Cigar Lake test mine under conditions similar to those expected at the Midwest mine. [The Midwest Project Environmental Impact Statement, Executive Summary, Cogema Resources Inc., August, 1995, p. 4.] This method involves the combination of two proven technologies -- ground freezing and jet boring -- to recover highly radioactive ore that is surrounded by very wet and incompetent ground. [The Midwest Project Environmental Impact Statement, Main Document, Cogema Resources Inc., August, 1995, pp. 2-10.]

6.1.1 Ground Freezing

To freeze the ore-bearing formation, sets of parallel freeze galleries would be mined in basement rock approximately 20 m below the ore body. From these galleries vertical holes would be drilled upward, extending to about 5 m above the ore body. Each hole would contain tubes through which brine, cooled to - 35^oC, could be circulated. After several months, the ground from the freeze galleries up to and above the ore body would be frozen. Entry to the freeze galleries would be via the existing Midwest test mine shaft, extended downward by some 60 m.

Freezing of the saturated and weak rock formations in which the ore is found should improve mine stability. Freezing should also limit the flow of radon-laden ground water into mine excavations. A portion of the remaining mine water inflow would be recycled for use in drilling and boring operations, thereby reducing the volume of water to be handled in the water treatment plant.

Approximately 650 exploration bore holes exist in the area where mining would take place. Many of these were drilled from Mink Arm into or through the Midwest ore body during exploration. Freezing of the ground around the ore body would prevent the inflow of water when bore holes are intersected during mining. Without the protection that freezing provides, it would be necessary to drain Mink Arm and dewater the area above the ore body. Ground freezing would therefore diminish the environmental damage that would have occurred if Mink Arm and the surrounding area were dewatered. It would also improve mine water management and increase radiation protection for the underground employees.

One of the reasons for the developing of this new mining method is that we cannot plug those bore holes.

V. Martin, Comega Resources Inc., Transcript of Midwest Public Hearings, Saskatoon, Saskatchewan, May 29, 1996, p. 93.

6.1.2 Jet Boring

Once the ground is frozen, a production gallery would be mined between, and about 10 m above, the freeze galleries. Although this gallery would be closer to the ore body, there would still be several metres of barren rock remaining to shield the workers from the radiation emanating from above. Casing holes would be drilled from the production gallery up into the ore body and the head of the jet-boring machine, extended above the casing, would cut up the frozen ore using high pressure water jets. The resulting ore-containing slurry, enclosed completely in piping, would be conducted under the force of gravity to a crusher/ grinder. This slurry would be thickened and hydraulically hoisted to the surface from where it would be transported to the JEB mill for processing. Use of shielded conduits throughout the mine would ensure that workers experience minimum exposure to the highly radioactive ore.

The combination of several metres of basement rock between the occupied production galleries and the ore body; the use of a non-entry mining method; and the use of sealed, ore-slurry transport methods to remove ore from the mine should shield underground workers adequately from exposure to radioactive ore. The use of automated mining procedures follows the current trends in mining technology used to improve protection for workers in dangerous underground mining environments. Jet boring, used in conjunction with ground freezing, is technically sound and appropriately designed to facilitate safe recovery of the high-grade Midwest ore.

6.2 Liquid Effluent and Discharge Location

The mining method described in Section 6.1 has positive implications when compared with the proposal reviewed by the panel in 1993. Mink Arm would no longer require draining, and there would be a considerable reduction in mine water inflow. Overall, Cogema predicts a volume of treated effluent that would total about 11 per cent of that predicted in the earlier proposal. [The Midwest Project Environmental Impact Statement, Main Document, Cogema Resources Inc., August, 1995, Table 2.1.5.3.] The volume of effluent would also be small relative to other Saskatchewan uranium mining operations, being less than half that released by Cluff Lake, which discharges the least effluent of the mines currently operating. Thus, the total environmental loading [Total environmental loading = concentration of contaminant in effluent x volume of effluent released.] of contaminants released to the environment would be small relative to the discharges from other uranium mines.

The question of whether the effluent should be discharged into North McMahon Lake or the Mink Arm of South McMahon Lake must be resolved before mining begins. Of the two locations, North McMahon Lake has the greater volume and greater water flow, permitting faster dilution of the effluent and a correspondingly quicker reduction in contaminant concentrations. However, this discharge location, which is farther from the mine than Mink Arm, would require the consideration of the impacts of a pipeline on the terrestrial environment, and increase the probability of treated water spills. Also, if an upset were to occur in the water treatment plant, any release of undesirable effluent could be mitigated more easily if it were discharged into Mink Arm rather than North McMahon Lake. Mink Arm is separated from the rest of South McMahon Lake by an earth dam, and the high placement of the culvert linking the two water bodies reduces the normal flow of water between Mink Arm and South McMahon Lake. Thus, although the release of undesirable effluent into Mink Arm would create a greater local impact compared to North McMahon Lake, the dam would provide more protection to water bodies downstream.

The panel supports the proposed choice of a discharge location at Mink Arm, but encourages Cogema to seek ways of reducing possible impacts in the discharge area. The location and method of discharge into Mink Arm should be selected in consultation with the Department of Fisheries and Oceans, Environment Canada, and the provincial department of Environment and Resource Management. If the impacts to Mink Arm prove to be unacceptable, mitigation would be required.

6.3 Waste Rock Disposal

Cogema proposes to dispose of mine waste rock at various locations. Depending on its potential to release contaminants, waste rock would be classified as either clean waste or special waste. Clean waste rock is characterized as containing less than 0.03 per cent uranium and concentrations of other elements below recommended limits. Special waste would be comprised of waste rock containing between 0.03 per cent and 0.09 per cent uranium, or elevated levels of arsenic, nickel or sulphur, either singly or in combination.

Some of the special waste, estimated to be approximately 204,000 tonnes in total, [The Midwest Project Environmental Impact Statement, Main Document, Cogema Resources Inc., August, 1995, pp. 2-47.] would be used to backfill mine galleries on the freeze and production levels when underground mining ceases. The remaining special waste about 116,000 tonnes [8 Ibid.] 8 would be transported to the McClean Lake property for disposal in the Sue C pit. Sludge materials resulting from the water treatment process would also be trucked to the McClean Lake site where they would be combined with mill tailings for disposal within the JEB pit.

Some of the clean waste would be used to prepare concrete for backfilling underground jet-bored cavities. The proposed method for disposal of the remaining clean waste, estimated to be 101,000 tonnes, [Ibid.] is as a 6-metre high by 100-metre square stockpile located approximately 200 m west of the Mink Arm shoreline. The proponent proposes to contour this stockpile, with slopes graded to less than 28^o, in order to minimize erosion and encourage revegetation. [Ibid, pp. 2-136.] Although this stockpile would occupy only a limited surface area, the mounded structure would be a new topographic feature along the western shore of Mink Arm.

There is concern that unintentional mixing of clean and special waste rock materials could occur in the surface stockpile. The EIS describes no procedures to guarantee the effective segregation of clean and special waste materials in a timely fashion. Should mixing occur, there might be increased discharge of contaminated leachate, which could affect surface water quality detrimentally. [L.M. Broughton, R.W. Chambers, A. MacG. Robertson, Mine Rock Guidelines, Saskatchewan Environment and Public Safety, April, 1992, p. 4-4 - 4-13.] It is, therefore, imperative that the proponent demonstrate a satisfactory method for differentiating between mineralized and non-mineralized waste rock before mining starts.

We agree with Environment Canada that Cogema should maximize the quantities of waste rock materials to be disposed of within the underground workings of the Midwest mine. Where quantities of clean or potentially contaminated waste cannot be disposed of in this fashion, an option other than the proposed stockpiling should be considered:

Environment Canada advocates the pit disposal of the entire remaining volume of Midwest waste rock and special waste at the McClean Lake site ... completely filling the Sue C pit....[Environment Canada, Prairie and Northern Region, Submission to the Midwest Project Public Hearings, Regina, Saskatchewan, June 10, 1996, p. 43.]

The panel endorses Environment Canada's advice that the proponent consider alternative disposal plans for mine waste rock. Clean and special waste rock that cannot be used as backfill in underground excavations should be disposed of in pits at the McClean Lake site. If this condition is not accepted and the stockpile proposed for the west side of Mink Arm is permitted, arrangements should be made to monitor it for several decades. A financial guarantee should be provided to ensure that any acid mine rock drainage from the stockpile can be mitigated. This could include eventual removal of the waste rock to one of the mined-out pits at McClean Lake. Monitoring of the site should involve the participation of local people as described in Section 4.4.

6.4 Conclusions and Recommendations

By creative use of a combination of mining techniques -- ground freezing and jet boring -- Cogema has proposed an acceptable plan for recovery of ore from the Midwest deposit.

The location of the discharge for liquid effluent should be in Mink Arm, with the method of discharge being determined in consultation with the Department of Fisheries, Environment Canada and Saskatchewan Environment and Resource Management.

The proponent should demonstrate an effective method for differentiating between clean and special wastes before mining starts.

All special waste rock and as much clean waste as possible should be disposed of underground in the Midwest mine, or in a mined-out pit on the McClean Lake site. The waste rock pile proposed for the west side of Mink Arm should be monitored for several decades. A financial guarantee should be provided to ensure that any acid mine rock drainage from the stockpile can be mitigated. This guarantee would be part of the Uranium Mine Contingency Fund described in Section 12.4. If acid-mine drainage is observed to occur, the waste rock should be removed to one of the mined-out Sue pits at the McClean Lake site.