Small tonnage ore bodies can be developed at a profit on a short life basis. Such is the case of the Bardon Mine in the Big Indian Mining District in San Juan County Utah. Faced with a small initial tonnage of high grade uranium ore, the Shattuck Denn Mining Corporation Engineers developed some new ideas for sinking the shaft and planned extraction to warrant the capital risk to mine a limited reserve.
Field experience in uranium has shown it is most economical to ram through a drilling program to obtain maximum footage per drill hour. Drift surveys can then determine the course of the holes. Using this method is generally cheaper than paying the additional cost involved in using the drilling technique and equipment necessary to maintain straight holes.
The shaft location was spotted about 120 feet south of the ore body to gain underground ore haul advantage due to the dip, for underground ore storage, minimum surface preparation, adequate plant area and for access.
The slot pocket was planned for volume underground storage and to avoid the handling costs due to packing in chutes. Ore is moved in the slot pocket by a 25 horsepower Vulcan double drum slusher placed at the end, 100 feet from the measuring pocket. The Pocket tender operates the slusher by air controls from his remote control station at the pocket.
Mining a tabular ore body lying on a 12 degree dip requires versatile equipment. Mucking machines and haulage units that are capable of negotiating 20 per cent grades and yet be operated efficiently and economically had to be found. A five foot head, air driven, trackless Eimco model 635 conveyor loader unit met the mucking requirements. This rugged unit mucks both uphill, and downhill on the dips encountered in the mine and carries about two tons in its hopper and conveyor. This latter feature is advantageous as the operator loads the machine while the haulage unit departs to the shaft with a load of ore and the second unit positions itself for a load. We have mucked as high as 100 tons an hour with the usage efficiency of the machine about 50 to 60 per cent. Because of the performance, we believe the Eimco 635 is the finest mucking machine; for the purpose on the market today.
Mine development and layout was planned after studying operations at the gadon Mine of Hecla Mining Company, the La Sal Mine and the North Alice Mine of Homestake Mining Company and much constructive discussion among many operators in the district.
The main haulage drift was driven due north to the extremity of the ore body and crosscuts were driven easterly and westerly offsetting one another on approximately 50 foot centers. Because of the variance in dips undulation of the floor and the non-conformity of the top of the ore, it was advantageous to maintain a level floor and to mine a clean back and roof bolt on three foot intervals through four foot sections of steel mat to support the back.
During the planning and construction of the surface plant, we were confronted with burying 400 feet of water line or developing some other means of protection against ffeezing, as temperatures often drop to 5 to 10 degrees below zero in winter.
