Northstar Materials Inc., dba Knife River Materials, has paid a $17,525 civil penalty to the Minnesota Pollution Control Agency (MPCA) for industrial wastewater violations at a nonmetallic aggregate mining facility near Mentor. The Bemidji-based company also submitted a plan for meeting its permit requirements, including instituting best management practices, installing floating silt curtains and earthen berms in its mine pit, and adding settling basins.
An MPCA staff inspection confirmed that sediment-laden mine pit water had discharged into Judicial Ditch 64, and then into nearby Lower Badger Creek. For 18 days, the company discharged dredged mine pit water to surface water — which is not permitted — and then installed berms to stop the discharge. The company’s discharges also exceeded permitted limits and caused nuisance conditions in surface waters. The company did not report the problems to the Minnesota State Duty Officer or the MPCA as required and failed to recover the sediment that had left the site.
The company was required to stop discharging dredged mine pit water directly to surface water at all of its sites. Also, the company had to submit a procedure for how to report and respond to discharges that exceed permit limits.