Agnico Eagle Mines Limited / Mines Agnico Eagle Limitee - Environmental Compliance Approval (sewage)

Public comments were considered when conducting the technical review of the ECA application prior to making the decision. 

The public comments with regard to the discharge of treated effluent into the Misema River from the industrial sewage works were considered during the technical review. The reviewer carefully reviewed the engineering design of the proposed sewage works and rigorously checked the wastewater treatment facility’s design performance against the effluent criteria imposed by the ministry regional staff. Technical comments on the engineering design were raised by the reviewer and responded to by the proponent’s engineering consultant. The reviewer also engaged the ministry regional and district staff multiple times during the review process to ensure that the site-specific conditions, effluent criteria, and monitoring programs be appropriately incorporated into the ECA.

Specific public comments on the limited operational flexibility (LOF), stormwater collection, impact of heavy rainfall, effluent criteria and effluent discharge devices were also taken into consideration when conducting the technical review. Where technical questions or concerns regarding these aspects were raised by the reviewer, responses from the proponent’s engineering consultant were reviewed and incorporated into the ECA as appropriate. The reviewer also followed the standard procedures to incorporate all relevant components into the ECA, including the LOF conditions, operations and maintenance conditions, effluent criteria, and monitoring programs, etc.

Detailed response to the comments received are as follows:

• Comments regarding the discharge of treated effluent from the mine wastewater treatment facility into the Misema River around its impact on human health and using the River and other downstream waters as a food and recreational source.

The ministry has issued an industrial sewage works Environmental Compliance Approval (ECA) to regulate the collection, treatment and disposal of industrial wastewater from the proposed advanced exploration project.

All process water, domestic sewage and stormwater in contact with mining materials will be collected and treated by technologies and processes (i.e. sewage works) reviewed and approved by the ministry prior to discharge into Misema River. The engineering design of the proposed sewage works was rigorously reviewed and checked against the effluent criteria imposed by the ministry staff in the ECA so that a final effluent meeting the set criteria can be produced. The effluent criteria were carefully set based on the ministry’s review of a surface water impact assessment (including an Assimilative Capacity Study) prepared by the proponent and numerous discussions between the proponent and the ministry. The thoroughly reviewed surface water impact assessment and carefully established effluent criteria ensure that the treated effluent poses low or little risk to human health and the environment.

The ECA sets out legally enforceable rules of operation and maintenance of the sewage works. These general and site-specific rules are designed to ensure proper and adequate operation of the sewage works and protect human health and the environment from discharges of contaminants produced by the mining activities.

The ECA also sets out legally enforceable rules of effluent, groundwater and receiving water monitoring. These general and site-specific rules are designed to require the proponent to evaluate and demonstrate the performance of the sewage works. A full suite of monitoring programs is included in the ECA, including effluent monitoring, groundwater monitoring, receiving water monitoring and hydrometric monitoring. The ECA also requires the proponent to record the monitoring results and submit them to the ministry for review on a regular basis.

To further enhance the protection of the Misema River and ambient environment, the ECA sets out conditions that require the completion of additional studies/programs by the proponent within a set timeframe. These studies/programs include a mixing zone validation assessment, a biological monitoring program and a stormwater control study.

In addition, the ECA is only applicable to the advanced exploration stage of this mining project. A condition in the ECA requires the proponent to apply for an amendment or new ECA should this mining project move beyond the advanced exploration stage.

With the rigorous review of the sewage works design and surface water/groundwater impact assessment, as well as the comprehensive enforceable conditions imposed in the ECA on effluent criteria, operations and maintenance, monitoring and recording, and reporting, it is in the reviewer’s professional opinion that the sewage works will not cause an adverse effect to human health and the environment if operated and maintained properly in accordance with the ECA.

• Comment regarding the definition of limited operational flexibility.

Under the Definitions section, the ECA defines “Limited Operational Flexibility (LOF)” as “the conditions that the Owner shall follow in order to undertake any modification that is pre-authorized as part of this Approval”. Essentially the LOF conditions provides the proponent with the flexibility to make pre-approved low-risk modifications to the sewage works without the need to go through the regular approval process. The LOF conditions also set out rules to ensure that any pre-approved modification will not negatively impact on the performance of the works.

• Comment regarding how stormwater will be properly collected considering site conditions (e.g., no pavement, site contour).

Based on the engineering drawings submitted and discussions with the proponent’s consultant, the site will be properly divided into catchment areas based on-site contour and grading to direct stormwater overland flows to the proposed collection ditch network and collection ponds.  

To protect groundwater resources (in case of contaminants coming in contact with groundwater through infiltration), the ECA imposes a comprehensive groundwater monitoring program for contaminants of concern. This includes the monitoring of 14 monitoring wells located within or in the vicinity of the site. Groundwater samples will be taken three times per year from each of these monitoring wells and reviewed by the ministry staff. Follow-up steps will be taken by the ministry Timmins District Office should there be any environmental concerns revealed by the monitoring results.

• Comment regarding the possibility of retention pond overflow due to extreme rainfall events and what actions will be taken.

The design of the main retention pond (Retention Pond #1) provides adequate capacity (45,574 m³) for two (2) back-to-back 24-hour 100-year storms with average snowmelt, in addition to the daily industrial and domestic sewage generated on site. This design is considered conservative considering the extremely low likelihood of the occurrence of two back-to-back 24-hour 100 year storms. A 1-metre freeboard, i.e. additional 16,073 m³ of storage, will be provided on top of the expected water volumes from the two back-to-back 24-hour 100-year storms, process water and domestic sewage, making the pond even less possible to overflow. In addition, the downstream industrial wastewater treatment plant will draw sewage from Retention Pond #1 at 500 m³/hour on a 24-hour basis (12,000 m³/day). This further reduces the risk of wastewater overflowing from the retention pond.

In the highly unlikely event of a pond overflow, it’s anticipated that the spill prevention and spill contingency plans required under Part X of the Environmental Protection Act will be triggered and implemented such that the overflow will be responded to and dealt with in an appropriate manner to eliminate or ameliorate any adverse effects to human health and the environment. 

• Comment regarding why the use of a diffuser at the discharge location will help with the discharge of contaminated water.

The water that goes through the diffuser is treated effluent that meets the imposed effluent criteria; the multiport submerged diffuser facilitates the mixing of treated effluent with the receiver water in a more effective manner to further minimize the impact of effluent discharge on the receiver.

• Comment regarding who established the effluent limits, who will check these limits and the monitoring results, and how often they will be checked.

The established effluent objectives and limits were proposed by the proponent and reviewed by the surface water specialists, hydrogeologists and hydrologists at the Technical Support Section from the ministry. Revisions and adjustments to the proposed effluent objectives and limits were made by the ministry staff upon review, and the finalized effluent criteria have been imposed in the ECA for compliance. The monitoring program imposed in the ECA, as specified in Condition 11 and Schedule D, dictates how often the parameters in the effluent objectives and limits are tested (e.g., daily, weekly, monthly, quarterly, etc.) and these results will be submitted to the ministry on an annual or more frequent basis for review. The samples will be collected by the proponent’s qualified operations staff and summited to third-party accredited laboratories for analysis, which ensures the standard testing protocols are followed.

• Comment regarding who will monitor the discharge volumes and how pond discharges will be controlled and measured.

The daily discharge volume will be monitored by the proponent’s operations staff via flow measurement devices upstream of the effluent disposal facility, as required by the flow monitoring condition 11.3 in the ECA. The daily discharge volume will be included in the annual report per condition 15.6.b., which will be reviewed by the ministry.

Discharges from Retention Pond #1 will be treated by the industrial wastewater treatment plant at a controlled rate. Fully treated effluent will be discharged to Misema River via an effluent pumping station at a controlled rate. The discharge flow will be measured by an approved online flow meter.