Tougher Requirements for Metal Mines – Metal Mining Effluent Regulations Amended

On May 30, 2018, the federal government published new regulations amending the Metal Mining Effluent Regulations (MMER) in the Canada Gazette. The amendments cap a long period of government consultation and corresponding advocacy by industry. The amendments will come into force between June 1, 2018, and June 1, 2021. There are approximately 130 metal mines in Canada subject to this important Regulation.

Mining operations produce effluent (e.g. waste water, tailings, and waste rock) that can contain harmful or “deleterious substances". The Fisheries Act (Canada), under subsection 36(3), prohibits the deposit of deleterious substances in water frequented by fish unless authorized by a regulation. The MMER authorizes the release of certain deleterious substances from metal mines into fish-frequented waters, provided that the concentration of these substances does not exceed the prescribed limits and the effluent is not acutely lethal to fish (as determined by a lab test).

Once in force, the MMER will apply to diamond mines and will be referred to as the Metal and Diamond Mining Effluent Regulation (MDMER). Diamond mines were previously not formally regulated through Fisheries Act discharge prescriptions.

One of the changes in the new version of the MDMER is that the allowed limits of many “deleterious substances” have been made more stringent for new mines or for existing mines that are closed and then reopened.

Beginning on June 1, 2021, the amendments establish more stringent limits for existing metal mines on arsenic, cyanide, and lead as well as add new limits for un-ionized ammonia. For these existing mines, the amendments do not change the limits for copper, nickel, zinc, total suspended solids, or Radium-226. However, for new mines that become subject to the MDMER on or after June 1, 2021, or recognized closed mines that reopen after this date, the amendments do impose more stringent limits for arsenic, copper, cyanide, lead, nickel, and zinc, as well as introduce limits for un-ionized ammonia.

A significant change that will affect mining companies the most is the obligation to ensure effluent is non-toxic for Daphnia magna (a small freshwater flea-like creature) as part of the prescribed lab test. As of June 1, 2021, the amendments require that mine effluent not be acutely lethal to Daphnia magna for mines to maintain their authority to deposit. An effluent is considered acutely lethal to Daphnia magna if the effluent at 100% concentration kills more than 50% of the Daphnia magna subjected to the effluent over a 48-hour period. The amendments provide a “one strike” exception, so that a first acute lethality failure for Daphnia magna would not be considered an event of non-compliance subject to potential enforcement, while subsequent failures would. Testing for toxicity by proxy is subject to high variability and error. There may be little connection between the bucket in the lab and the actual receiving environment.

The amendments also allow for the use of a marine species, the threespine stickleback, to test for acute lethality as an alternative to rainbow trout when saline effluent is being released into marine environments.

Finally, the amendments make some changes to the Environmental Effects Monitoring (EEM) requirements. Fish tissue studies are now required for selenium. Additionally, new substances have been added to the list of those to be monitored in the EEM studies. Some EEM requirements have been relaxed for those receiving environments that have established track records of lower impacts.

Metal Mining Effluent Regulations MMER Metal and Diamond Mining Effluent Regulation MDMER Environmental Effect Monitoring EEM Fisheries Act



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