OCR

The Marcona Downhill Conveyor System 17-Mile Haul to San Juan During the period 1953 through 1961 the direct shipping ores were hauled from the mine area to the screening and shiploading facilities at San Juan by trucks. The distance from the mine loading hopper to San Juan is 1 7 miles, with a drop in elevation through this distance of approx- imately 2450 ft. Except for one short level section, it is downhill the entire distance with the severest grade being 6.5 percent. Early in the beneficiation plant planning, the advisability of locating the beneficiation complex north of San Juan about 12 miles, at the bay of San Nicolas, was considered at length. There were several important advantages to the San Nicolas location, including: 1) The bay would lend itself nicely to a pier long enough and in water deep enough to accommodate the loading of specialized ore carriers in sizes upwards of 100,000 DWT: 2) ship loading rates and port stockpile facilities could be increased and modernized without affecting mine production or shipping rates at San Juan; 3) the plants could be constructed without being cramped or restricted by the expanding urban development at San Juan; 4) the planning could include consideration for future growth and step-by-step plant additions and proces- ses to take care of the gradually changing qualities of the ore. Route to San Nicolas Had Obstacles A. formidable obstacle to this planning was the problem visualised in moving large quantities of ore from the mine to San Nicolas . The, direct route from the mine to San Nicolas does not have the same moderate but steady slope to sea level as the route from the mine to San Juan. Instead there is a relatively flat section of about 4. 7 miles, then a sharp escarp- ment covering about 1. 5 miles, and then another flat section of about 4. 3 miles to San Nicolas. The terrain over this route, particularly at the escarpment, provided a challenge of the first magnitude. Three haulage possibilities and combinations of these possibilities were considered: 1) A combination of truck and belt conveyors, whereby conveyors would handle the steep down-slope at the escarpment, 2) A railroad from the mine to San Nicolas over a route determined by the maximum slope possible with current day rail equipment, and 3) Expansion of the existing truck haulage operation, which would mean moving the required tonnage from the mine to San Nicolas via San Juan.