A taconite processing plant on the North Shore of Lake Superior will pay $240,000 in fines for violating air quality standards.
The Minnesota Pollution Control Agency said the plant exceeded permitted levels for fine dust about 30 times over a six-month period.
The MPCA said Northshore had not violated the limits during the previous 20 years.
The dust comes from moving and stockpiling of taconite pellets. The company is now using more water and chemical dust suppressants to keep the dust down.
Company spokeswoman Sandy Karnowski said the violations could have been related to the weather.
"It was particularly windy and dry during that time period, and that played a role in the dust events that we had," Karnowski said.
MPCA spokesman Steve Mikkelson said it's also paying for new ambient air monitors to be used around the state.
"That's a good thing to not just correct the problem there but also help with monitoring at locations throughout the state," Mikkelson said.
The monitors collect samples every six days. Based on weather conditions and other data, the MPCA calculated that a total of nearly 30 air quality violations occurred on both monitored days and days with no monitoring.
The plant's owner, Cliffs Natural Resources, this week announced record revenues of nearly $7 billion worldwide.