OCR

1964 Pima Doubles Capacity The Pima Mining Co., 20 miles southwest of Tucson, Ariz., is planning ahead to 1967. This will be the important year when first production will come from its new Northeast pit--now being developed--and ____ present Pima pit will be phased out. By this time nearly $8 million will have been spent in a carefully planned and engineered 6-year program of expansion and transition. This program entails: (1) doubling milling capacity to 8, 000 tpd. ; (2) providing additional ore storage and surge capacity; (3) purchase of new open pit equipment; (4) modification of the loading facilities at the skip hoist; (5) stripping 200 ft. of alluvium from the Northeast ore body; (6) completing an exploration drilling program; (7) studies of the Northeast ore body; (8) transfer of all mining activities to the new Northeast pit (1967). In 1960, management of the Pima Mining Co. (50 percent owned by Cyprus Mines Corp. , 25 percent by Utah Construction and Mining Co. and 25 percent by Union Oil Co.) recognized the inevitable fact that ore Reserves in the Pima open pit would be depleted in a few years. However, after the Pima ore body was discovered in the early 1950's, a large zone; of low-grade, copper-bearing ore was found to exist by drilling so the northeast. Thus the future of the company was clearly in this direction, and feasibility studies were ordered. These were completed in 1961, and mining of the Northeast ore body was judged economically sound. After due consideration, the board of directors gave the green light to proceed with project in the latter part of 196l. Up until this time, mining in the Pima, pit was on a basis of 3,000 to 4,000 tpd. This tonnage was handled by 2-1/2 cu. yd. shovels, 20-ton trucks, and a skip hoist with two 20-ton capacity skips. To increase the output of the pit to supply the newly-planned 8,000 tpd. mill capacity, various pieces of new pit equipment and changes were required. The problem of getting more production from the pit was solved by the Pima engineers who proposed: (1) modifying and increasing the capacity of the present truck haulage fleet; (2) purchase of larger capacity trucks which would eventually be used in the new pit; (3) purchase of two larger capacity electric shovels that would also see service in the new pit; and (4) adding two 40-ton surge bins at the skip hoist loading station. The fleet of ten 20-ton tracks was modified by adding 14-in. steel sideboards to the dump boxes. This had the effect of increasing carrying capacity to approximately 27 tons or about 12 cu. yd. A fleet of eight