Opinion ID: 1281848
Heading Depth: 1
Heading Rank: 2

Heading: Present Operations at Silver Bay and Proposed Plan for Mile Post 7

Text: Reserve Mining Company is jointly owned by Armco Steel Corporation and Republic Steel Corporation. It presently extracts taconite ore from the Peter Mitchell Mine near Babbitt, Minnesota. Reserve beneficiates the ore (prepares it for smelting) by a process of crushing, grinding, and magnetic concentration, producing pellets of high grade ore which are transported on the Great Lakes to Armco and Republic Steel mills. The Silver Bay plant produces about 10.4 million tons of taconite pellets annually, representing 17 percent of the taconite produced in the United States and accounting for about 8 percent of the nation's iron ore consumption. At the Babbitt mine site a crushing process begins which reduces the ore to rocks 4 inches or less in size. The ore is then transported 47 miles by railroad to Reserve's processing plant located at the city of Silver Bay. At the plant, further crushing occurs to reduce the size of rocks to less than three-fourths of an inch. In the concentrating process which follows, water is introduced into the system and the mixture is subjected to repeated grinding, magnetic and hydraulic separation, sizing, rejection of non-magnetic waste material as tailings, and removal of the water. The iron concentrate is then mixed with bentonite, dehydrated, and put into balling drums which produce pellets of approximately one-third of an inch in size. In the final stage, the pellets are subjected to extremely high temperatures, which hardens them and changes their chemical properties from magnetic oxide of iron to hematite. Presently not all of the tailings which are discharged into a delta in Lake Superior reach the trough at the bottom, and a substantial number, which remain buoyant, continue to circulate in the lake. This is the activity which the Federal court has enjoined if an on-land site is not completed by April 15, 1980. Reserve proposes to spend over $300 million in building an on-land tailings disposal site at Mile Post 7 and in modifying its processing plant to abate the emission into the ambient air of amphibole material which may contain pathogenic fibers of amosite asbestos. The principal change in the processing of ore at Silver Bay will be the construction of facilities to produce what is called dry cobbing by which high intensity magnetic separators will isolate 22 percent of the ore into coarse tailings. These gravel-size tailings will be transported by conveyors to Reserve's railroad which will haul them 7 miles to a tailings basin to be located at Mile Post 7. Other coarse tailings, having the consistency of sand, will be treated in a similar manner. Fifty-nine percent of the tailings, consisting of fine silt, will remain and will be mixed with water and pumped approximately 5 miles in a 24-inch slurry pipeline to the tailings basin where the water will be recycled and returned to the plant by a separate pipeline. The dam which contains the tailings will be filled with water to a depth of approximately 10 feet to reduce the quantity of fugitive dust generated by the use of an on-land disposal site.