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<br /> <br />powered rubber-tired equipment is used in the mining process (Figure <br />2-2). <br />2,2 ORE-HAULAGE RAILWAY <br />The railway begins as a tunnel on the edge of the ore body <br />at an elevat~n of 7,500 feet (about 4,800 feet below the summit of <br />Red Mountain). ~-.The tunnel runs west for 9.6 miles, surfacing at an <br />elevation of 9,000 feet near the confluence of the Williams Fork River <br />and Darling Creek on the western slope of the Continental Divide. It <br />is the longest railroad tunnel in the U.S. (third largest in the <br />world) and required four years to complete. Driving proceeded simul- <br />taneously from both ends during the last two years of construction. <br />The use of a gyroscope and laser-beam guidance system resulted in <br />negligible survey error when the headings met. <br />After surfacing, the railway continues west and north for <br />another 4.8 miles to the mill site. Figure 2-3 shows the tunnel <br />portal site as it appeared in 1976. <br />The railway is continuous double track and accommodates six <br />fully automated 42 inch gauge electric trains. Each train consists of <br />up to thirty 22-ton, bottom-dump ore cars and four 50-ton locomotives. <br />The trains are computer controlled and dump on 17-minute intervals <br />after a 1-1/2-hour round trip. <br />2,3 MILL, CRUSHER, CONCENTRATOR AND TAILING DEPOSITION SITE <br />The ore processing facilities (mill, crusher and concen- <br />trator) are located on the ridge between the Williams Fork River and <br />2-4 <br />