Minnesota Considers Use of Taconite to Fix, Construct Roads

Minnesota Considers Use of Taconite to Fix, Construct RoadsApr. 11 – Within 20 years, Minnesota’s seven-county metropolitan area will run out of aggregate due to urban sprawl and commercial development.That’s when coarse tailings, a waste product produced at Iron Range taconite plants, could become a valuable commodity as an aggregate replacement for road construction and fill.A report developed by the Natural Resources Research Institute in Duluth, Minn., recommends that market uses for the taconite tailings be expanded beyond northern Minnesota.It’s among more than two dozen mining reports to be presented Tuesday and Wednesday at the 77th meeting of the Society of Mining Engineers and 65th University of Minnesota Mining Symposium at Duluth Entertainment and Convention Center.Hundreds of mining engineers, executives and experts attend the annual convention to hear about new technologies, processes and trends.Taconite tailings are particles of waste rock that remain after the crushing and ore separation of taconite. They vary in size from the clay-like consistency of fine tailings to larger particles called coarse tailings.The 30-month NRRI study found coarse tailings offer superior drainage, fill and durability characteristics when used as aggregate and in road construction.”It’s been used in our part of the state, and we think it’s a good idea to look at using it elsewhere,” said Larry Zanko, an NRRI researcher who worked on the report. “The goal is to get it to other areas of the state and Midwest that are facing aggregate shortages and rising aggregate prices.”While taconite tailings can’t be use in a concrete mix, their use in an asphalt mix for road construction has shown promise. Since the early 1960s, tailings have been used as a base to build roads across the Iron Range. In the 1970s, tailings was mixed with asphalt oil and turned into a bituminous for resurfacing.It’s popularity dipped for a time in the 1980s due to high oil prices, but in the 1990s surged again for road construction.Iron Range taconite plants have for years used tailings to cover taconite plant roads. Some Iron Range homeowners apply it to their driveways.But it’s use to build durable, long-lasting highways could help alleviate aggregate shortages and provide taconite plants with a new source of revenue.The five western Iron Range taconite plants included in the study generally produce more than 30 million tons of tailings per year.”The need exists, and it’s a good use for a taconite product,” said Frank Ongaro Jr., president of the Iron Mining Association of Minnesota.”As much as the state, the region or the country needs, it is there and it can be made available.” Tailings from the five mines were found to be environmentally sound for aggregate use. Tailings from two East Range mines, Northshore Mining Co. and portions of the former LTV Steel Mining Co., can’t be used as aggregate for public use. Following the Reserve Mining Co. controversy of the 1970s, in which asbestos-like fibers were found in East Range tailings, then-Gov. Wendell Anderson signed an executive order prohibiting use of the tailings from the East Range plants.At the five West Range plants, tailings are stored within basins and used in road construction or fill within the mining properties.Aggregate experts say it’s a perfect time to investigate the economics and logistics of using tailings in other areas of Minnesota and neighboring states.”There’s about five-to-10 years of aggregate left in the Maple Grove area for the northern suburbs,” said Fred Corrigan, director of the Burnsville-based Aggregate and Ready Mix Association of Minnesota. “And there’s about a 20-to-30 year supply left in Dakota County. When that’s gone, we are out.” In 2001, the Minnesota Department of Transportation used 80,500 tons of tailings for Iron Range road projects. Usage increased to 127,000 tons in 2002 before declining to an unknown amount in 2003.Highways 37, 53 and 169 on the Iron Range all have had portions resurfaced with tailings/asphalt mixtures.In 2004, MnDOT officials expect to use about one million tons of tailings within northeastern Minnesota’s District 1, primarily for reconstruction of the Highway 53 and Highway 169 interchange north of Virginia.”It’s an equal substitute to natural aggregates,” said Kevin Adolphs, a MnDOT District 1 engineer in Virginia. “There are some inherent benefits because it is crushed material, and it’s a durable rock that has angular edges. It has a higher friction factor that on highways prevents skidding.” Former MnDot Commissioner Elwyn Tinklenberg, who is now president of The Tinklenberg Group, his own Blaine-based transportation consulting business, says several states are anxious to explore the use of tailings as aggregate.Dwindling aggregate resources and restrictions on the permitting of new aggregate pits have transportation officials in North Dakota, South Dakota, Wisconsin, Pennsylvania, Iowa, Indiana, and Illinois interested in tailings, he said. In some states, only softer natural aggregates such as limestone and sandstone, which aren’t as durable as taconite tailings, are being used in road construction.”This really meets a terrific demand,” said Tinklenberg. “It holds up well, has good abrasion for traction and doesn’t hold moisture.” Efforts are underway to secure federal funding for a two-year program that would test long-term durability characteristics and help market the use of taconite tailings as an aggregate to other states.Some states, such as Florida, have been forced to delay economic development projects due to a lack of aggregate, Tinklenberg said.Last year, Brainerd International Raceway resurfaced its quarter-mile drag strip with an asphalt mixture containing taconite tailings from the former EVTAC Mining Co., now United Taconite.”It created a lot of attention,” said Scott Quick, BIR general manager. “There wasn’t a race track in the country that used this as an aggregate.” The new track proved to be smooth, durable and fast, Quick said. A new world speed record in American Motorcycle Association Prostar competition was set along with a new U.S. record for National Hot Rod Association alcohol dragsters.”It works fantastic,” said Quick, who is attempting to get other drag strips around the country to utilize tailings. “If you compare taconite tailings with rock aggregate, it provides a surface porosity that is smooth and it also provides traction.” Quick says he would like to resurface BIR’s 3-mile road course with a tailings mix to showcase its benefits to state transportation. A federal House Transportation Committee grant would help that effort, he said.Granite and limestone aggregate costs about $2 to $3 per ton. Coarse taconite tailings, costs about $50 cents to $1 per ton, according to Fred Corrigan of the Aggregate & Ready Mix Association of Minnesota. If a taconite producer charges more than 50 cents a ton, that amount would be profit for the taconite company.Sand and gravel, which also is used as an aggregate is cheaper to produce than granite or limestone — about 50 cents to $1 per ton.Developing a rail system to economically transport the tailings from the Iron Range to storage areas near the Twin Cities remains a major obstacle to expanded use.Tailings typically cost about 50 cents to $1 per ton. Transporting tailings by truck costs about 10 cents per ton per mile, not including loading and unloading costs, which can run from 50 cents to $1 per ton.”Once you get beyond 50 miles from its source, trucking is too expensive,” he said. “The biggest thing people are trying to overcome is to find a way to get it by rail to the northern suburbs.” Shipping tailings by boat from Duluth to states such as Michigan, Indiana or Ohio and southern states might be possible in coming years, Corrigan said.An upcoming takeover of the Duluth Missabe & Iron Range Railway by Canadian National Railway could help open up new rail lines for tailings transportation.”When the Twin Cities runs out of aggregate, that’s when everybody will be searching for material, and the Iron Range is certainly on the horizon,” Corrigan said.By Lee
Bloomquist, Duluth News-Tribune, Minn.

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