Late last week, the Minnesota Department of Natural Resources (DNR) released two draft dam safety permits and a draft public waters work permit for public review and comment. These are two of the major permits Polymet Mining needed to build and operate its NorthMet copper-nickel-precious metals project in northeastern Minnesota. The draft public waters work permit is required for a culvert extension to widen Dunka Road, the connecting road between the plant and mine site.
Dam safety permits establish the design, construction and operating parameters to ensure long-term, safe and stable operations of facilities that impound water. PolyMet has proposed two facilities to impound water: an existing tailings basin and a new hydrometallurgical residue facility. The DNR posted the draft permits for a 30-day public review and comment period.
“These draft permits account for three of nine permits that have been noticed for public review and comment this summer,” said Jon Cherry, president and CEO, Polymet Mining. “We are pleased with our progress and look forward to the rest of the draft permits being released.”
An existing tailings basin was an integral part of historic iron ore mining operations between 1957 and 2001. PolyMet will reuse this basin and incorporate additional engineering controls into the design to ensure it remains stable and protects nearby natural resources during and after operations. Using the existing tailings basin affords less wetland impacts and beneficial reuse of a brownfield site. The new hydrometallurgical residue facility will impound water and solids from the hydrometallurgical processing plant, and will have a double liner containment system.
Geotechnical experts independently performed numerous geotechnical evaluations during environmental review and permitting, and concluded it is feasible and safe to store NorthMet tailings using an existing tailings basin at the site, enhanced with technologies such as a rock buttress and monitoring devices.
“The tailings basin was one of the most studied aspects of the NorthMet project during the comprehensive state and federal environmental review of the project that concluded in 2016,” Cherry said. “We take the design, construction and operation of the tailings impoundment very seriously and have taken extra measures to ensure a safe and stable design. The science shows that not only can we be protective of water and other natural resources, but we will make a substantial contribution to addressing legacy reclamation issues at the site.”
Other permit applications currently under review by the state include a water quality permit (National Pollutant Discharge Elimination System/State Disposal System or NPDES/SDS permit), an air emissions permit, and the Permit to Mine. Meanwhile, the 30-day public review and comment period for six draft water appropriations permits released last month by the DNR ended September 12.
The draft dam safety permits and draft public waters work permit as well as other permit applications and their status are posted on www.polymet.mn.gov. The website also provides information about the permitting process conducted by the DNR and Minnesota Pollution Control Agency.