Great Lakes tankers are required to have double hulls and are escorted by icebreakers in winter. Because of a career spent in fresh water, the Great Lakes vessel's average life expectancy is 40 to 50 years, twice that of a vessel operating in salt water. The mills employ 90,000 workers. Ore mines in Minnesota and Michigan employ 8,000 workers. Coal for power generation is the second-largest commodity volume carried.
Eastern coal is mined in West Virginia and Kentucky, Pennsylvania and Ohio.
Western coal is mined in Montana and Wyoming. Journal Sentinel Inc. All rights reserved.