Analysis of Proposed Change to the Lynn Lake Gold Project – Pit Dewatering

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Document reference number: 129

Draft Report
March 2025

Contents

• 1. Introduction
• 2. Proposed Project Change
• 3. Consultation and Engagement
  • 3.1 Proponent's Engagement with Indigenous groups
  • 3.2 IAAC's Engagement on Project Change
• 4. IAAC's Analysis of Changes
• 5. Assessment of Potential Adverse Environmental Effects
  • 5.1 Fish and Fish Habitat
  • 5.2 Current use of lands and resources for traditional purposes
  • 5.3 Other valued components
• 6. Conclusion

List of Figures

• Figure 1. Map of proposed discharge point and discharge line path.

List of Tables

• Table 1 – A summary MCFN's key concerns related to the proposed change to the Project and the explanation provided by the Proponent
• Table 2 – Recommended amendments to the Decision Statement

1. Introduction

The Lynn Lake Gold Project (the Project), as proposed by Alamos Gold Inc. (the Proponent) and approved by the Impact Assessment Agency of Canada (IAAC) involves the construction, operation, decommissioning, and reclamation of an open pit gold mine and new metal mill located approximately 1,000 kilometres north of Winnipeg, near the Town of Lynn Lake, Manitoba. The Project involves the redevelopment of two historical gold mines (the Gordon site and MacLellan site) and has an ore input capacity of 8,250 tonnes per day over a 13-year period. Components of the Project include new mine infrastructure, a new distribution line, open pits, access roads, an ore milling and processing plant, ore and overburden stockpiles, mine rock storage areas, and a tailings management facility.

The Project was subject to an environmental assessment under the Canadian Environmental Assessment Act, 2012 (CEAA 2012) conducted by IAAC. On March 6, 2023, the Minister of Environment and Climate Change issued a Decision Statement (Canadian Impact Assessment Registry Reference number 80140, Document Number 125) for the Project that contains 177 legally binding conditions, which include mitigation measures and follow-up program requirements that the Proponent must comply with throughout the life of the Project. The amended Decision Statement in July 2024 (Canadian Impact Assessment Registry Reference number 80140, Document Number 127) to reflect changes to the Impact Assessment Act (IAA) pursuant to section 308(1) of the Budget Implementation Act, 2024. Based on information provided by the Proponent, construction of the Project began in February 2025.

Alamos Gold, Inc. must submit to IAAC for review any proposed changes to the Project as it was originally described, as required by condition 2.16 of the Decision Statement. On February 9, 2024, Alamos Gold, Inc. notified IAAC of proposed changes to the Project in a document entitled Lynn Lake Gold Project: Gordon Mine Pit Dewatering Notice of Alteration/ Notice of Change (Canadian Impact Assessment Registry (CIAR) Reference number 80140, Document Number 131) which details a change in the discharge location of water from existing flooded pits at the Gordon Site. Additional information related to the Project change was provided October 18, 2024 and December 20, 2024 (CIAR Reference number 80140, Document Numbers 132 & 133).

IAAC has conducted an analysis of the proposed changes to the Project and the potential adverse environmental effects of those changes, including additional impacts on the exercise of rights of Indigenous groups, to assess:

• whether the changes constitute a new or different designated project that may require a new impact assessment; and
• whether any changes (including addition or removal of conditions) may be required to the Decision Statement, including the mitigation and follow-up program measures included as conditions, to address the proposed Project changes.

IAAC's analysis is summarized in this report.

2. Proposed Project Change

The Project, as originally approved, includes the dewatering of two existing flooded pits at the Gordon Mine Site, known as the Wendy and East pits, to allow for the development of an open pit. As part of the existing Project, the water from these pits would be released over the course of several years into Farley Lake, which lies adjacent to the Gordon site, before continuing into the Hughes River via Farley Creek.

To decrease the time required to dewater the Wendy and East pits and the resulting environmental risks associated with dewatering over several years into the Farley Lake/Farley Creek system, the Proponent is proposing to change the pit water discharge location from Farley Lake directly to the Hughes River, at a discharge point roughly 8 km south at the existing Hughes River bridge along the Gordon Site Access Road (Figure 1). The pit water would be transported to the Hughes River using a temporary dewatering system consisting of long segments of hose placed on the ground surface that would run adjacent to the Gordon Site Access Road to the Hughes River Bridge. These hoses would be removed following the completion of dewatering. Because of the greater capacity of the Hughes River relative to Farley Creek, dewatering would occur over a period of three months during the operation phase instead of over several years.

Aside from the change in the discharge location and the longer discharge line, the removal of water from the Wendy and East Pits for deposit into the receiving environment has already been assessed and approved as part of the original environmental assessment (Canadian Impact Assessment Registry Reference number 80140, Document Number 124). This includes aeration of both pits throughout dewatering to improve the pit water quality and the monitoring of the water quality prior to release into the receiving environment.

3. Consultation and Engagement

3.1 Proponent's Engagement with Indigenous groups

In its Notice of Change to IAAC, the Proponent indicated that it engaged with the 13 Indigenous groups named in the Decision Statement through the established Environmental Advisory Committee (EAC) for the Project. Indigenous groups were either informed directly during EAC meetings (held from October 2023 though August 2024) or through distribution of the minutes of these meetings which were shared with all Indigenous groups.

The Proponent conducted additional engagement with Marcel Colomb First Nation (MCFN) on the Project change through MCFN-specific subcommittee meetings of the EAC with MCFN advisors and through meetings with MCFN community members, leadership and advisors to discuss the details of the Project change, answer questions and address concerns.

3.2 IAAC's Engagement on Project Change

IAAC has sought the expertise of Environment and Climate Change Canada (ECCC) and Fisheries and Oceans Canada (DFO) to inform the assessment of potential adverse environmental effects related to proposed changes to the Project, as presented below in section 4.

IAAC will engage with the 13 Indigenous groups listed in the Decision Statement (Barren Lands First Nation, Chemawawin Cree Nation, Hatchet Lake First Nation, Manitoba Métis Federation, Marcel Colomb First Nation, Mathias Colomb Cree Nation, Métis Nation – Saskatchewan Eastern Region 1, Métis Nation – Saskatchewan Northern Region 1, Nisichawayasihk Cree Nation, Northlands Denesuline First Nation, O-Pipon-Na-Piwin Cree Nation, Peter Ballantyne Cree Nation, and Sayisi Dene First Nation) to validate the views presented in this report and invite these Indigenous groups to provide any further comments related to the Project change, IAAC's analysis report or recommended amendments to the Decision Statement.

In addition, IAAC will be seeking further comments from federal authorities and the public on the proposed changes to the project as part of the public consultation period.

Feedback provided during Indigenous consultation and during the public consultation period will be taken into account in IAAC's final analysis report and recommendations for amendments to the Decision Statement on the Project change, which will be provided to the Minister of the Environment and Climate Change to inform decision making.

4. IAAC's Analysis of Changes

The Physical Activities Regulations (the Regulations) under IAA identify the physical activities that constitute designated projects that may require an impact assessment. IAAC is of the view that the change does not constitute a new or different designated project that may require a new impact assessment.

5. Assessment of Potential Adverse Environmental Effects

5.1 Fish and Fish Habitat

5.1.1 Views of the Proponent

The Proponent indicated that fish and fish habitat could be affected through changes to surface water quantity (i.e., increase in flow) and quality (i.e., change in temperature and concentrations of substances) and disturbances from discharge infrastructure (i.e., installing the dewatering equipment and the discharge line to the Hughes River).

In its analysis, the Proponent predicts effect on surface water flow to be negligible. The Proponent explains that the Hughes River volume is two orders of magnitude greater than pit dewatering flows, such that water quality will be dominated by existing conditions within the Hughes River during dewatering. The Proponent notes that the modelling of water flows corroborates this. During dewatering, flows in the Hughes River are expected to increase between 1% and 2%. The Proponent notes this is well below the 10% change threshold suggested by the Department of Fisheries and Oceans Canada (DFO) and the minimum change to have a detectable impact on an aquatic ecosystem that supports commercial, recreational, or Indigenous fisheries in Canada.

Additionally, effects on surface water quality are also expected to be negligible. Although baseline water quality on the Hughes River exceeds the water quality guidelines for some months at some locations for total aluminum (Al), dissolved lead (Pb), and dissolved zinc (Zn), modelled surface water concentrations for these parameters, as well as dissolved manganese (Mn) and total arsenic (As) did not exceed any of the water quality guidelines for any mixed modeling scenario at any location in the Hughes River downstream of the discharge location. Impacts to Hughes River water temperature and dissolved oxygen are similarly expected to have negligible effects.

The Proponent also notes that pumping the pit water directly into the Hughes River eliminates the risks to fish and fish habitat within Farley Lake and Farley Creek given the larger volume of water and greater capacity of the Hughes River relative to Farley Lake and Farley Creek. The proposed shorter dewatering timeframe (3 months) avoids sensitive periods for fish, including spring spawning periods, and reduces the associated risks of operating dewatering equipment in the winter months. The Proponent is of the opinion that, overall, this proposed dewatering location change is less harmful to the environment and fish and fish habitat than the original approved discharge location through Farley Lake and Farley Creek.

To mitigate the potential effects to fish and fish habitat through changes in surface water quantity and quality, associated uncertainty with these predictions and disturbances from discharge infrastructure resulting from the proposed change, the Proponent noted a series of mitigation measures that will be applied which include aeration of the Wendy and East pits, installation of end of pipe screens to protect fish, conducting work in and around water within least risk timing windows for fish, implementation of measures for sedimentation and erosion control, and temperature management of pit lake water as required.

5.1.2 Views Expressed

Environment and Climate Change Canada (ECCC) did not express concerns overall with the change in discharge site location or the rate of discharge following review of the Proponent's Notice of Change and additional materials. ECCC did note, however, uncertainties associated with only one year of baseline data and the lack of temporal variability it provided. In their review of the Notice of Change, ECCC highlighted the importance of the pit dewatering monitoring program to reduce uncertainty and monitor discharge quality from the pits and water quality in the Hughes River. ECCC noted that the monitoring program is not reflected in the existing federal Decision Statement.

DFO also did not express any concerns overall with the change in discharge site location or the rate of discharge following review of the Notice of Change and additional materials. DFO did note additional information would be required for the purposes of a Fisheries Act authorization, but that it was not necessary for the analysis of impacts related to the Project change. DFO advised that the changes to the existing mitigation and follow-up measures should be updated in Decision Statement conditions to account for the change in discharge location, including conditions 3.5, 3.5.1, 3.5.2, 3.6, 3.13.1, and 3.14.4.

5.1.3 IAAC's Analysis and Conclusions

Most measures described by the Proponent to mitigate the effects of the Project change were already considered during the original environmental assessment and described in the existing Decision Statement, including aeration of the Wendy and East pits (3.5.1), installation of end of pipe screens to protect fish (3.3), conducting work in and around water within least risk timing windows for fish (3.8.2), and implementation of measures for sedimentation and erosion control (3.11) and temperature management of pit lake water as required (3.5.2). IAAC is recommending changes to federal conditions within the Decision Statement (see Table 2) to update the definition of Designated Project (1.7) so that the existing conditions apply to the Project change. In response to advice from ECCC and DFO, IAAC is also recommending updating the language related to the location of pit dewatering discharge in mitigation measures and follow-up programs and to reflect the additional monitoring proposed by the Proponent in their dewatering monitoring plan.

5.2 Current use of lands and resources for traditional purposes

5.2.1 Views of the Proponent

Discharge into the Hughes River and any resulting changes to river flow and water quality have the potential to impact the current use of the Hughes River by Indigenous groups, namely MCFN who fish and camp downstream of the discharge site. However, the Proponent did not identify residual effects on current use of lands and resources for traditional purposes given that residual effects to Hughes River flow and water quality were negligible.

5.2.2 Views Expressed

Over the course of the Proponent's engagement on the Project change, MCFN raised concerns about long-term impacts to the Hughes River water quality and subsequent impacts to downstream spawning shoals for fish including pickerel (Sander vitreus), riparian wildlife and water supply for camps. In November 2024, the MCFN community voted to oppose the proposed change to the Project for these reasons. Subsequent meetings between the Proponent and MCFN chief and council, advisors, and community members were held in early 2025 where the Proponent heard more about these concerns and clarified details of the proposed change to the Project and associated effects and mitigation. MCFN indicated to IAAC that MCFN may consider holding another community vote soon following these clarifications. Table 1 summarizes MCFN's key concerns and the explanations provided by the Proponent.

Of the 12 other Indigenous groups consulted, only O-Pipon-Na-Piwin Cree Nation voiced concerns, specifically that discharge would impact South Indian Lake. The Proponent explained that South Indian Lake would not be impacted as it is not in the same watershed.

5.2.3 IAAC's Analysis and Conclusions

IAAC notes that MCFN concerns about sedimentation and erosion were considered during the original assessment and addressed in the existing Decision Statement, including requirements to implement measures for sedimentation and erosion control (federal condition 3.11) and to use diffusers (federal condition 3.11.2). IAAC recommends modifications of the existing Decision Statement to incorporate additional Proponent commitments made in response to MCFN's concerns, including the addition of the Proponent commitment to avoid discharge during spring spawning (3.5.3), and MCFN's requested additional monitoring components related to dewatering (see new 3.12.3). In consideration of MCFN's request to participate in the dewatering monitoring program, condition 2.9 of the existing Decision Statement requires the Proponent to discuss opportunities for Indigenous groups to participate in follow-up program activities including monitoring, analysis and reporting, as well as opportunities for training and support. IAAC has included reference to condition 2.9 in the new condition 3.12.3 to reiterate this requirement in the context of the dewatering monitoring program.

5.3 Other valued components

The Proponent did not identify any additional valued components beyond fish and fish habitat and water quality that would be affected by the Project change. It explained that the Project change impacts are limited to the discharge location and any terrestrial modifications from the temporary pumps and hoses will occur within an existing disturbed area and developed road right-of-way. No excavation or earth disturbance is proposed. The rationale for exclusion of these valued components is described in Table 3-1 of the Notice of Change.

6. Conclusion

Based on the information provided by the Proponent, federal authorities and Indigenous groups to date, it is IAAC's conclusion that the proposed changes to the Project are not likely to cause significant adverse environmental effects beyond those described in the 2023 environmental assessment, taking into account the mitigation measures and follow-up programs included as conditions in the Decision Statement.

Since the proposed changes to the Project are not included in the definition of the Designated Project as currently described in in the Decision Statement, IAAC recommends that this definition be modified to include the new discharge location for pit dewatering. This amendment will ensure that the conditions included in the Decision Statement also apply to the proposed changes to the Project.

Additionally, IAAC proposes modifications to certain conditions to reflect the changes in references to the discharge location, related predictions and commitments made by the Proponent during consultation with Indigenous groups.