Contact: Steve Mikkelson, 651-316-3887
Duluth, Minn. ― Northshore Mining Co. has agreed to pay a $240,175 penalty to the Minnesota Pollution Control Agency (MPCA) for air-quality violations that the MPCA says occurred at the company’s taconite-processing plant in Silver Bay. The violations were for emissions of excessive amounts of very fine dust that is unhealthy to breathe.
Northshore is also taking steps to prevent future violations, including emission-control improvements at its large taconite pellet storage yard.
Between November 2010 and May 2011, ambient air quality monitors located between the taconite pellet storage yard and the Silver Bay marina measured violations of permit limits for particulate matter, or dust, smaller than 10 microns (PM10) in width, or about one-fourth the diameter of a human hair. Dust deposits were also documented at the Silver Bay marina. PM10-size dust is one of the federal and state governments’ health-based standards that help determine the levels where exposure can compromise human health.
Because Northshore’s permit requires monitoring to be conducted once every six days, the agency calculated that nearly 30 air-quality violations occurred on monitored days and on days when no monitoring was conducted. This calculation of expected violations is required as part of the federal PM10 compliance determination method.
Northshore has taken corrective actions to limit and control dust emissions, including increased use of water cannons and other water sprays used for dust control during the transfer and stockpiling of taconite pellets, pellet screening, and in the truck dump area. The company has also increased its use of chemical dust suppressants. Northshore will also mulch exposed areas in the pellet yard, and provide additional dust-control training for its workers. The company is required to investigate additional methods to prevent future emissions and dust-related deposits at nearby sites, including the marina. To measure the success of these corrective actions, the company will begin daily PM10 monitoring between the marina and the taconite pellet storage yard.
In addition to paying the penalty and improving its dust-control capabilities, Northshore offered to spend $79,825 to replace older MPCA ambient air monitors across the state that measure smaller dust particles with seven new, continuously operating monitors. These monitors measure particulate matter smaller than 2.5 microns in size (a human hair is about 40 microns in diameter). They will provide higher-quality, regulatory-grade monitoring data for use in demonstrating compliance with ambient-air-quality standards, and in helping evaluate future projects, including new or expanded mining projects.
The stipulation agreement between Northshore Mining and the MPCA is one of the tools that the MPCA uses to achieve compliance with environmental laws. When calculating penalties, the MPCA takes into account how seriously the violation affected the environment, whether it was a first-time or repeat violation and how promptly the violation was reported to appropriate authorities. The agency also attempts to recover the calculated economic benefit gained by failure to comply with environmental laws in a timely manner.
For more information, go to the MPCA website at www.pca.state.mn.us.