In 2019, Canada approved an extension of the deadline to start one of the world’s largest copper and gold mines in the headwaters of the transboundary Unuk River (1). The plan for the Kerr-Sulphurets -Mitchell (KSM) mine is to dig one of the largest human-made holes on earth, erect one of the highest dams in North America, and operate water treatment for 200 years after the mine closes (2). Mines such as KSM pose long-term risks to downstream water quality, fish, and people (3). Given that mine contamination is not constrained by political boundaries, U.S., Canadian, and Indigenous governments must urgently engage in collaborative evaluation and regulation of mines in internationally shared rivers. Shortfalls in mine assessments and permitting policies should be addressed.
Mine assessments underestimate risk at high environmental cost. Contributing factors include the ecological complexity of rivers, policy shortcomings in weighing environmental risk (4), and profound engineering challenges posed by mountain mining. For example, insufficient evaluation of soil stability enabled the 2014 catastrophic failure of the Mount Polley tailings dam (5).
Furthermore, the issuance of mine permits relies on the promise of mitigations that lack field validation. Canadian industrial projects typically underdeliver on their mitigations, such as restoring fish habitat (6). Unverified technologies can fail, as evidenced by the 2014 fish kill downstream of Teck Resources’ wastewater treatment plant (7).
Finally, mine assessment and permitting do not require incorporation of transparent, independent, and peer-reviewed science (8). For example, Teck’s Elk Valley permit allows contaminant discharges up to 65 times above scientifically established protective thresholds for fish (9). Political borders do not block the downstream flow of this contaminated water into Montana and Idaho (10).
Stakes are high. Upstream Canadian mines threaten downstream economies, waters, and ways of life, even as the United States is currently weakening its own federal environmental regulations (11). Rather than a race to the bottom, we urge our governments to honor their mutual obligations to protect our shared transboundary waters as codified in the Boundary Waters Treaty of 1909 (12) and immediately collaborate on binational environmental reviews that are founded upon independent, transparent, and peer-reviewed science.