In terms of policy, this should be part of the integrated river basin management for the Mackenzie River basin. There are vast natural ecosystems downstream, and indigenous populations in a relatively lower political power jurisdiction. The Northwest Territories is not a province.
The stance of many of the indigenous people is zero tolerance for contamination of their waters. That has to be assured through transboundary agreements and through a strong Mackenzie River Basin Board that has the authority to ensure that environmental conditions downstream are being met all the time.