Mountain Iron, Minn., Taconite Mine Wrestles with Wastewater Disposal
Dec. 4Where do you put 7.2 million gallons of unwanted water every day?
That's what officials of the Minntac taconite plant are trying to determine, waiting for a Minnesota Pollution Control Agency decision on the company's plan to pump water from its Mountain Iron, Minn., taconite tailings basin into a nearby river.
After studying the issue for more than three years, PCA officials say they'll complete a draft environmental impact statement early in 2005.
The PCA is considering several options for the water, including the original plan to route it down the Dark and Sandy Rivers in northeastern Minnesota. A new option would send the water south, into the West Two Rivers Reservoir, which flows into the St. Louis River system and, eventually, into Lake Superior.
The problem is that the water contains sediments and sulfates, and the sheer volume makes it an issue no matter where the PCA looks for an outlet.
"We're still working on it. The draft (EIS) is over 600 pages now and looks at 10-to-12 options," said John Elling, PCA project manager.
They include one to refrain from taking action, with no additional diversion allowed out of the Minntac tailings basin. Another is to require a treatment plant clean the water before it's released. Only one other Minnesota taconite plant, North Shore Mining, is required to treat water that leaves its tailings basin.
In 2001, officials of the U.S. Steel-owned plant first proposed to divert 5,000 gallons of water per minute 2.6 billion gallons per year out of its tailings basin. That basin is where the unused mining waste rock from the taconite processing plant goes along with millions of gallons of water every day.
Minntac uses about 250,000 gallons of water every minute of every day for various parts of the taconite making process, including separating ore from rock, cleaning air pollution scrubbers and moving waste rock into the tailings basin.
The basin itself, a giant storage area ringed by more than nine miles of dikes, can hold 18 billion gallons of water. It's not in danger of overflowing, but company officials say discharging water would extend the basin's life.
Minntac has for 30 years recycled much of that water. But the repeatedly recycled wastewater is becoming choked with solids, and the company wants to let some of it out. Using cloudy water to make pellets can affect their quality and foul plant equipment, PCA officials said.
The water diversion "is something we really still need," said John Armstrong, U.S. Steel spokesman in Pittsburgh. "After 30 years of recycling water, we need to make some changes." Minntac already has a permit that allows 2,200 gallons of water per minute to "seep" out of the tailings basin. Elling said diversion would allow a more controlled release.
Minntac and the PCA have encountered environmental concerns in almost every direction they've looked to dump the water, which contains sediment and small amounts of pollutants, such as sulfates.
The huge volume could overwhelm small streams and raise stream temperatures, both of which could affect fish populations and stream ecosystems.
Sulfates are considered a possible human health issue because they can trigger mercury in the streams to become toxic, called methyl mercury, which can build up in fish and then in people who eat fish.
"The impact of mercury is the biggest issue no matter where the water goes but the volume of water is probably a bigger issue on the Dark (river). It would have the biggest impact there," said Karl Koller, Grand Rapids area fisheries specialist. "Adding that much warmer water might put the river past the temperature that will sustain trout." Minntac officials asked for the extensive environmental impact statement to determine what impact the diversion would have on local waterways.
The original plan to pump the water north into the Dark River was met with opposition from trout anglers, including the Grand Rapids Trout Unlimited chapter. The river is one of the best naturally producing trout streams in the area.
A proposal to send the water east into the Sandy River brought concerns about downstream areas of wild rice, which are sensitive to water levels and where sulfates can damage rice germination.
A new option looking at the St. Louis River system almost certainly will bring warnings from downstream interests, including environmentalists and anglers in Duluth.
Elling noted that other taconite plants already have water diversion permits; the Minntac request is not unprecedented.
Studies so far have shown sulfates as the biggest problem, but not an insurmountable one, said PCA hydrogeologist Richard Clark. Concerns over heavy metals in the tailings water so far have proven unfounded, he said.
"Fortunately, the concentrations of metals and mercury in both the tailings basin water and the seepage have been very low," he said. "Metals are not our primary concern. It's sulfates." The DNR's Koller said the best option may be some sort of treatment of the water to remove sulfates.
"We're going to be learning more about that in the next few weeks," Koller said. "Treatment of some sort may be the best way to solve one of the bigger problems. And then we still have to decide which way to send it, or decide to split up the volume several directions." The public will have 45 days to comment on the draft plan when its released next year, and a public meeting on the proposal is expected. A final plan would also have a public input period before the plan goes to the full PCA citizens board for approval, possibly later in 2005.
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© 2004, Duluth News-Tribune, Minn. Distributed by Knight Ridder/Tribune Business News.