Environmental Monitoring for Metal Mines in Canada: Requirements, Risks, and Strategies
In 2002, the Canadian Metal Mining Effluent Regulations (MMER) came into effect. The regulations apply to all operating metal mines that discharge at least 50 m3 per day of effluent into a receiving body of water, and in Schedule 4 of the MMER effluent limits are prescribed for identified ‘deleterious substances’. Schedule 4 currently includes effluent limits for As, Cu, Pb, Ni, Zn, TSS, and 226Ra, and also requires effluent pH to be between 6.0 and 9.5 and to be non-acutely lethal to Rainbow Trout. Metal mine operators in Canada are required under the MMER to regularly monitor for the tests and substances listed in Schedule 4 of the MMER, and are currently >98% compliant with the prescribed limits. However, the MMER is currently being reviewed and Environment Canada has proposed alteration of Schedule 4 to include the addition of new substances, including Al, Fe, Se and ammonia, the reduction of effluent limits for existing substances by two- to six-fold, and the addition of the Daphnia magna acute lethality test. These proposed alterations, if implemented, may require expensive upgrades to effluent treatment for continued compliance. It is, therefore, critically important for mine operators to be aware of these potential alterations and additions to the MMER, and to review and assess their mine’s current effluent chemistry and toxicity against the proposed alterations to Schedule 4 of the MMER.
The MMER also includes Environmental Effects Monitoring (EEM), which requires mine operators to monitor fish health, fish tissue, and benthic invertebrate community structure. The EEM program is an iterative and escalating series of monitoring cycles that currently culminates in an Investigation of Cause (IOC). Because of structural, analytical and statistical deficiencies inherent in the EEM program, it is almost certain that every mine will confirm ‘effects’ under the current EEM program. The identified deficiencies, however, can be countered through a variety of strategies, including inclusion of multiple reference sites, use of Bonferroni correction, recalculation of the Bray Curtis Index, and use of Critical Effect Sizes (proposed) in interpretation of the results. These approaches will increase the cost of the EEM program, and may result in conflict with Environment Canada staff, but will reduce the liability of the EEM program to the mine. Monitoring requirements of the EEM program can also be substantively reduced through dilution of effluent: if effluent concentration is <1% at 250 m downstream of the discharge, then fish health monitoring is not required, and if effluent is <1% at 100 m downstream, then benthic invertebrate monitoring is not required (proposed). These considerations have become increasingly important because Environment Canada has proposed addition of Investigation of Solutions (IOS) into the EEM program. Implementation of identified solutions has the potential to affect all aspects of mine operations, and potentially cost mine operators tens to hundreds of millions of dollars.