The company's Silver Bay taconite-processing plant emitted excessive dust about 30 times over 12 months.
The Minnesota Pollution Control Agency has fined Northshore Mining Co. in Silver Bay $240,175 for violating air pollution laws 30 times in 2010 and 2011 -- the company's third fine in the last year and a half.
In addition, Northshore has agreed to buy seven state-of-the-art air monitors for a total of $80,000, which will accelerate the agency's ability to track fine-particle air pollution across the state.
Northshore Mining is owned by Cliffs Natural Resources in Cleveland.
The company's taconite-processing plant in Silver Bay was found to be generating excessive dust, a federally regulated pollutant that can cause serious heart and lung ailments. The problem was first identified by boat owners at the Lake Superior marina in Silver Bay after they repeatedly found their boats covered with dust from the nearby operation.
Northshore Mining has addressed the problem, and no violations have occurred since the spring of 2011, officials said. It improved its operating procedures and employee training, and added water spray systems and water cannons to control dust. It also added vegetation in the yard and roads suppress dust.
"Northshore Mining regrets any impact these dust events may have had on neighboring communities and visitors to the area," said Jim Korpi, the company's general manager.
The company mines taconite in Babbitt, then ships it by train to Silver Bay, where it processes 6 million tons of ore per year. The ore is stored in piles and frequently moved, which is when the dust problem occurs, said Bob Beresford, the state official who managed the case.
About 30 dust violations
Air monitors, which take measurements every six days, showed that dust levels exceeded federal limits five times between May 2010 and May 2011. That means violations occurred about 30 times, Beresford said. Although the company has been cited for other air quality violations, it's the first time it exceeded levels for dust, or particulates.
But the fine was one of the largest the agency has issued in the past year because dust can have significant health effects, from both short-term and long-term exposures. The particles are small enough to work their way deep into the lungs, and even into the bloodstream. Even a one-day event can trigger heart and asthma attacks and strokes. Long term, they contribute to chronic lung diseases and heart disease.
"That is one of the more significant types of violations that we address," Beresford said.
The company suggested that instead of a larger fine, it would provide the high-quality air monitors, which were on the MPCA's wish list for improving its air monitoring program statewide.
The state manages about 120 air monitoring devices at 60 stations around the state. One of the seven new devices will be installed on the Iron Range at Virginia, a new deployment. The others will replace older, less-sophisticated models.
Josephine Marcotty • 612-673-7394