1978-05-01_HYDROLOGY - M1977493 - Laserfiche WebLink

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2. Cycloning System The Mayflower Cycloning System is now complete and in operation. This system cyclones mill tailing into two fractions. The course free-drain- ing fraction is used for the initial building of the Mayflower Dam while the slime fraction is being deposited on the existing Tenmile Tailing Pond. The existing tailing ponds at Climax have been constructed by the up- stream method. In this method, tailing slurry is spigoted along the crest line. Deposition on the crest by spigot results in separation of particle size with the coarsest fraction staying at or near the crest, and the finer (slime) fraction deposited along the beach to the water pool. Because of this particular separation from spigot deposition, silt lenses can and do develop, resulting in a significant reduction in the vertical permeability within the body of the settled sand. This in turn has the effect of shifting the phreatic surface in the downstream direc- tion with its final location close to the downstream face. This condi- tion has a very significant influence on the stability of the dam. In 1974, in recognition of the above problem and that Mayflower would be the final tailing dam for the Climax operation, it was decided that cy- cloned material would be deposited in the dam foundation area. Cycloning removes the slime fraction (-200 mesh) from the tailing material, and will insure adequate stability when the tailing dam is constructed to its ulti- mate height of 557 feet. Due to the configuration of the pond, some two years of cycloned sand must be placed in the dam before the pond is put into conventional service. Cy- cloned sand deposition is presently planned to be accomplished by the end of 1978. Conventional tailing deposition as presently used on Tenmile and Robin- son ponds will be started on Mayflower when the required amount of cycloned sand has been deposited in the dam foundation. This sand blanket , which will be the width of the valley, will be 170 feet thick at the toe. It will extend upstream to a point beneath the ultimate crest, and will contain approximately 3-million tons of sand (12% minus 200 mesh) . In July of 1977, the cyclone facility was completed and testing started. By mid-August, cycloned sands were being deposited behind the Mayflower Toe Dam. The system was put into operation with very few startup problems. The Cyclone Station, with fourteen (14) D-26B cyclones, was constructed ad- jacent to existing Tenmile Pond at an elevation of 11, 100 feet. From this station, cyclone overflow is discharged by gravity directly into Tenmile Pond. The cyclone underflow is diluted and transported through 14,000 ft. of 16- inch high density polyethylene pipeline for deposition on Mayflower.