Northstar Materials, Inc., doing business as Knife River Materials, has paid a $17,252 civil penalty to the Minnesota Pollution Control Agency (MPCA).
According to a Monday, March 29 press release from the MPCA, the penalty is for industrial wastewater violations at a nonmetallic aggregate mining facility near Mentor, Minn.
The Bemidji-based company also submitted a plan to meet its permit requirements, including best management practices, floating silt curtains, earthen berms and settling basins.
An inspection by MPCA staff found that sediment-laden mine pit water had discharged into Judicial Ditch 64, then into nearby Lower Badger Creek. For 18 days, the company discharged dredged mine pit water to surface water, which is not permitted, then installed berms to stop the discharge.
The discharges exceeded permitted limits and caused nuisance issues in surface waters, the release said. The company did not report the problems to the state duty officer or the MPCA as required, and failed to recover the sediment that had left the site.
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The MPCA has required the company to stop discharging dredged mine pit water to the surface water at all of its sites, and to submit a procedure for reporting and responding to discharges that exceed permit limits.
The release notes that MPCA rules are designed to protect public health and the environment from harm caused by pollution emissions and discharges from facilities. Penalties are calculated based on how seriously violations could affect the environment, whether they are first-time or repeat violations, how promptly they were reported to authorities and the economic benefit the company gained by failing to comply promptly with environmental laws.
