1993-03-22_REVISION - M1977378 - Laserfiche WebLink

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Sunnyside Gold Corp. Page 9 March 10, 1993 The Brenneman-Sunnyside B-Level bulkhead is approximately 70 feet below the Lake Emma outflow and approximately 500 feet below the overlying ground surface. The Brenneman-Sunnyside B-Level bulkhead should complete the isolation of the Sunnyside Mine from the Brenneman-Mogul Mine by forcing any groundwater that may enter the Sunnyside Mine to exit through the Lake Emma outflow. Metallic sulfide oxidation products will be primarily, if not solely, from mine workings above the Lake Emma outflow elevation. Impounding water in the Sunnyside Mine has the additional advantage of significantly reducing the availability of oxygen to metallic sulfide minerals. The Sunnyside Mine stopes below the Lake Emma outflow are presently open to air and percolating groundwater. Oxidation of metallic sulfides exposed in mine workings requires only oxygen, water and time to produce metallic and sulfate ions. The reduced oxygen availability when the stopes are flooded will significantly reduce the oxidation rate for exposed metallic sulfides. The restricted flow paths for water impounded in the mine will resist the replenishment of oxygen necessary for the oxidation process. The thermal gradient within the mine is the only energy source available to drive the convection process necessary to replenish oxygen depleted water within the Sunnyside Mine. This low strength energy source should be relatively ineffective in replenishing the oxygen content of the impounded water because of the flow restrictions presented by the mine workings. The timbered shafts in the Sunnyside Mine represent the only reasonable convection path for movement of impounded water. The shafts in the Sunnyside Mine were deliberately placed outside the high-sulfide orebodies to protect them from mining operations. As such, shafts represent a minor potential contributor to metallic sulfide oxidation product production. Abandoned stopes probably represent the major potential source for metal and sulfate ions. Draw chutes below stopes were, doubtless, timbered over when the stopes were abandoned. Any rock falling from the hanging wall of the abandoned stopes and now sitting on the timbered draw chutes will further resist convective movement of impounded water. Water flow up or down ore passes in the Sunnyside Mine will be restricted because of the draw chutes at their bases. Rock which will also have raveled from the walls of the ore passes and which is currently lying on top of the draw chutes will further restrict water flow up or down the ore passes. The design locations of the four bulkheads will restrict the potential for chemical attack on the concrete because of the difficulty in replenishing the sulfate ion concentration at bulkhead locations. The thermal gradient differential over the height of a tunnel is so small that it is doubtful that it would be sufficient to circulate water from the roof to the floor, let alone hundreds to thousands of feet along a tunnel to a water filled shaft. The American Tunnel bulkhead is 2486 feet from the nearest