OCR

after a former tribal chairman, is operated by the Navajo Tribe as a recreational facility for residents of nearby communities. It has been stocked with hundreds of thousands of fish and is a favorite spot for fishermen, water skiers and other water sports enthusiasts. Electrical energy from the Four Corners Power Plant is delivered to population centers in Arizona over a 345, 000-volt transmission line. This line, nearly 300 miles in length, is one of the longest lines of this voltage in the United States. It is the only line of this voltage carrying steam generated energy. The engineering department of APS Co. employed a computer to determine the best tower sites and designs, an innovation in the industry, and by so doing saved the company $800,000. Plant at Mine Site The erection of the generating plant at the mine site is a relatively new development in the electric utility industry. Extra high voltage trans- mission has made such mine-mouth plants feasible through the reduction in cost of coal energy by wire to the point where it Is competitive at the point of consumption with other more mobile forms of energy. Coal thus con- sumed and transported produces a minimum revenue requirement for the electric utility company. Supervising the operation of the Four Corners Power Plant is Hugh W. Cocklin, who previously held a similar position at the APS Co. Saguaro Power Plan north of Tucson. The entire plant is operated and maintained by a staff of only 40 men. Although Utah Construction St Mining Co. began its corporate existence in 1900, it was not until 1943 that the company made its initial venture into mining which has since been expanded to a fully integrated mining organization operating three continents. The company first engaged in coal stria mining for the Pittsburgh Coal Co. , Pennsylvania, in the period 1943 to 1949. A metallurgical coal mine near Ozark, Ark. , was then acquired which termina- ted its 11-year life in 1960 when open pit reserves were exhausted. In 1953, Utah began prospecting for coal on the Navajo Reservation and today its strip mining activities are in full sway at the Navajo Mine. If Shifts per Week At the Navajo Mine, Utah currently is stripping 15 shifts per week and loading hauling on a one shift, five day per week schedule to produce 7. 000 tons, a coal daily; ultimately the company expects to produce 20, 000 tons per day from the leased area, a parcel of land 25 miles long by one mile wide running roughly in a north-south direction. Determining where, and how to begin mining operations Involved extensive study. The coal lies at a dip of 1-1/2 degrees and has overburden depths varying from 20 to 120 feet. The mining operation b;gins on the up- dip side of the lease where the coal lies under about 25 feet of medium hard rock. Here the overburden is drilled by track-mounted,- rotary rigs and then shot with ammonium nitrate prills.