Lynn Lake Gold Project

Analysis of Alamos Gold Inc.'s Proposed Changes to the Lynn Lake Gold Project – Gordon Site
Draft report

PDF Version 3.3 MB

Document reference number: 169

June 2026

On this page

• 1. Introduction
• 2. Proposed project changes
  • 2.1 Analysis in accordance with the Physical Activities Regulations
• 3. Consultation and engagement
  • 3.1 Proponent engagement with Indigenous groups
  • 3.2 IAAC consultation with Indigenous groups, federal authorities and the public
• 4. Assessment of potential adverse environmental effects
  • 4.1 Fish and fish habitat
  • 4.2 Health of Indigenous Peoples
• 5. Conclusion
• Annex I: Schedule 1 - Description of the Designated Project

List of Tables

• Table 1. Amendments to the Decision Statement recommended by IAAC

List of Figures

• Figure 1. Map of the Gordon mine site area .

1. Introduction

The Lynn Lake Gold Project (the Project), as proposed by Alamos Gold Inc. (the proponent), 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 would involve the redevelopment of two historical gold mines (the Gordon Site and MacLellan Site) and have an ore input capacity of approximately 8,250 tonnes per day over approximately 17 years. 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 Impact Assessment Agency of Canada (IAAC) conducted an environmental assessment under the Canadian Environmental Assessment Act, 2012 (CEAA 2012). On March 5, 2023, the Minister of Environment and Climate Change issued a Decision Statement for the Project that contains 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 Decision Statement was first amended on July 26, 2024, to align with the transition provisions set out in the Budget Implementation Act, 2024, then on August 6, 2025, to update the mine pit dewatering discharge point at the Gordon Site, and again on February 20, 2026, to make changes to the planned infrastructure for the MacLellan Mine site (CIAR Reference number 80140, documents 127, 143 and 161). An update to the Decision Statement was made on April 27, 2026, to include the use of the non-acid-generating historical mine rock storage area located to the north of the open pit of the Gordon Site, as a source of construction borrow material (CIAR Reference number 80140, documents 164). Based on information provided by the proponent, construction of the Project began in February 2025.

On October 6, 2025, the proponent notified IAAC of proposed changes to the Project, in accordance with condition 2.16 of the Decision Statement. This report summarizes the proposed changes and provides an analysis of whether they constitute a new or different designated project under the Physical Activities Regulations under the Impact Assessment Act (IAA). It also assesses whether the changes could result in increased adverse environmental effects within federal jurisdiction compared to those identified in the 2023 environmental assessment. In addition, the report considers whether any modifications to the conditions in the Decision Statement, such as additions or removal, may be necessary to address the proposed changes. The analysis is based on information provided by the proponent, and feedback received from federal authorities and from Indigenous groups.

2. Proposed project changes

The proponent has proposed a series of refinements to the Gordon Site, as described in the Notice of Change submitted to IAAC on October 6, 2025. These changes reflect advanced detailed engineering and mine planning undertaken since the issuance of the federal Decision Statement and provincial Environment Act Licence.

The proposed changes include modifications to the mine plan and site layout, an increase in total mined tonnage, and adjustments to several project components and water management features as shown in Figure 1. The refinements recover and optimize infrastructure layout, improve operational efficiency, maximize resource recovery, and minimize new environmental disturbance by increasing reliance on existing site features.

The proponent proposes to increase the total mined tonnage at the Gordon Site by approximately 12%, primarily due to a reduced cut-off grade and a revised open pit design. This increase does not change the approved production schedule or mine life but results in an expansion of the open pit footprint.

Detailed engineering has also resulted in changes to the layout and footprint of several project components within the Project Development Area (PDA), including adjustments to the mine rock storage area (MRSA), expansion and reconfiguration of ore and overburden stockpiles, siting of additional facilities and supporting infrastructure, and refinements to water management infrastructure such as sumps, collection ponds, interceptor wells, and the discharge pipeline. As a result of these changes, the overall PDA for the Gordon Site would increase from approximately 269 hectares to approximately 291 hectares representing an 8.2% increase.

In addition, the proponent proposes to remove the previously approved diversion channel between Gordon Lake and Farley Lake, as updated engineering and modelling indicate that it is no longer required to support project operations or environmental protection objectives. Removal of the diversion channel would reduce physical disturbance relative to the approved project design.

A new project component is also proposed involving the use of a historical, non-acid-generating MRSA located north of the open pit as a construction borrow source. This proposed change was addressed separately through the updated Decision Statement issued on April 27, 2026.

The proponent has further requested that water quality monitoring no longer be required in Arbor Lake, noting that it is substantially larger than the lakes potentially affected by the project (Minton Lake and Payne Lake) and therefore no longer serves as an appropriate reference site. The proponent proposes Carr Lake as a replacement reference lake, as it is more comparable in size and characteristics to the potential impact lakes.

Figure 1 - Text Version

Map showing project infrastructure for Gordon site, existing access roads, diversion channels, wetlands, and waterbodies are marked with different line styles and colors, with a legend explaining symbols and a north arrow for orientation.

2.1 Analysis in accordance with the Physical Activities Regulations

The Physical Activities Regulations under the IAA identify the physical activities that constitute designated projects that may require an impact assessment, including cases where the area of mining operations would increase by 50% or more. Section 19(c) and 19(d) of the Physical Activities Regulations read as follows:

19 The expansion of an existing mine, mill, quarry or sand or gravel pit in one of the following circumstances:

(c) in the case of an existing metal mine, other than a rare earth element mine, placer mine or uranium mine, if the expansion would result in an increase in the area of mining operations of 50% or more and the total ore production capacity would be 5 000 t/day or more after the expansion;

(d) in the case of an existing metal mill, other than a uranium mill, if the expansion would result in an increase in the area of mining operations of 50% or more and the total ore input capacity would be 5 000 t/day or more after the expansion;

Based on the proponent's submission, the proposed changes would increase the area of mining operations by 8.2%. As the proposed changes would not result in an increase in the area of mining operations by 50% or more, they do not meet the definition of a designated project as defined in sections 19(c) nor 19(d). Therefore, IAAC is of the view that the proposed changes do not constitute a new or different designated project.

3. Consultation and engagement

3.1 Proponent engagement with Indigenous groups

The proponent's Notice of Change indicated that engagement with Indigenous groups has been ongoing through established project mechanisms, including the Environmental Advisory Committee and Nation-specific engagement. The proponent reported that all Indigenous groups identified in the Decision Statement for the Lynn Lake Gold Project were informed of the proposed changes and that a draft Notice of Change was shared with all Indigenous Nations prior to final submission. Nation-specific engagement was undertaken with Marcel Colomb First Nation and Mathias Colomb Cree Nation through written exchanges and meetings, including a meeting held on December 9, 2025. This meeting was between the proponent and Marcel Colomb First Nation, with participation by IAAC, to review proposed mine plan changes and discuss responses to previous correspondence and information requests regarding the MacLellan site Notice of Change. The proponent committed to continued dialogue and information sharing with Marcel Colomb First Nation, with feedback to be shared with IAAC as part of the ongoing regulatory process.

3.2 IAAC consultation with Indigenous groups, federal authorities and the public

As part of the review process, a public consultation period will be held on proposed amendments to the Decision Statement and draft analysis of the changes. IAAC will be inviting comments from Indigenous groups, federal authorities as well as the public. Comments will inform IAAC's analysis and recommendations for amendments to the Decision Statement.

4. Assessment of potential adverse environmental effects

4.1 Fish and fish habitat

4.1.1 Proponent's assessment

Water quality

The proponent predicts that the proposed changes to the Gordon Site will result in moderate, localized, and long-term effects on fish health, growth, or survival, while the overall spatial extent, timing, and ecological context of effects on fish and fish habitat would remain consistent with those previously assessed in the Environmental Impact Statement (EIS). Updated surface water quality modelling, including refinements to model calibration and expanded parameter analysis, indicates that fluoride and total phosphorus remain contaminants of potential concern. In addition, nitrite (during operations in Farley Lake) is identified as a new contaminant of potential concern linked to changes in assumptions about residual nitrogen from blasting.

The proponent indicates that exceedances are generally limited in magnitude, phase-dependent, and not predicted to be persistent across the project lifecycle. Several parameters (including iron, manganese, and aluminum) exhibit seasonal fluctuations, while others (e.g., molybdenum, nickel, selenium) may increase during specific phases, particularly post-closure, but are expected to remain within or near applicable thresholds for the protection of aquatic life.

The proponent predicts a moderate magnitude residual effect, characterized as a measurable but non-population-level change in fish health metrics. To address potential effects on fish and fish habitat, the proponent proposes to rely on existing water management, monitoring, and follow-up programs, including the Surface Water Management and Monitoring Plan, which incorporates updated guideline application (including federal and site-specific criteria), trend analysis, and adaptive management triggers.

The proponent identified refinements to mitigation and adaptive management measures in its responses to Information Requests, including design-level controls and operational adjustments to manage potential effects on water quantity and quality; however, these measures represent refinements to the existing mitigation and monitoring framework rather than the introduction of a substantively new mitigation approach.

The proponent also indicates that adaptive management measures would be implemented if monitoring identifies exceedances of applicable guidelines or adverse trends. The proponent further states that existing mitigation, monitoring, and follow-up programs are expected to appropriately manage potential effects on water quality, and that the proposed changes are not anticipated to materially alter the nature or significance of previously predicted effects.

Water quantity

The proponent also predicts changes to surface water quantity in several waterbodies and watercourses resulting from the updated project design and water management approach. Flow reductions in Farley Creek during winter (approximately 23% to 43%) and during the open-water season (approximately 11% to 13%) are predicted; however, these changes are not anticipated to measurably affect fish habitat, given the tolerance of resident species and the limited ecological sensitivity of the system.

The proponent indicates that removal of the planned new diversion channel modifies drainage pathways and reduces the contributing drainage area to Gordon Lake, resulting in changes to inflows, outflows, and downstream flows (including in Farley Creek). However, the proponent also emphasizes that hydrological connectivity between Gordon Lake and Farley Lake is maintained via an existing diversion channel and generally presents these changes as alterations in the magnitude of flows rather than a fundamental change to the system.

The proponent indicates that predicted changes to surface water quantity associated with the proposed modifications are not expected to result in harmful alteration, disruption or destruction (HADD) where within established ecological thresholds; however, where changes may affect fish habitat (e.g., previously unidentified fish-bearing areas), these would be incorporated into the project's habitat offsetting plan and addressed through the Fisheries Act authorization process.

4.1.2 Views expressed

Water quality

Environment and Climate Change Canada (ECCC) notes that potential effects on water quality related to nitrite associated with blasting agents can be mitigated through effective source controls and best management practices during blasting. ECCC notes that nitrite, nitrate and ammonia is not currently included in condition 3.14.2, which requires water quality monitoring for contaminants that may have adverse effects on fish and fish habitat. ECCC recommends amending condition 3.14.2 to include nitrite, nitrate and ammonia, noting that these nitrogen compounds are linked through the nitrogen cycle and that nitrite is an intermediate product between ammonia and nitrate.

Water quantity

ECCC notes that there appears to be a discrepancy in the reported groundwater travel times originating from the South MRSA and Farley Lake, relative to travel times to other receptors. This inconsistency persists even where receptors are located farther from the source than Farley Lake or are hydraulically connected or adjacent to it (e.g., interceptor wells).

Given that Farley Lake is likely hydraulically connected to the southern historical MRSA and the mining pits, the seepage pathways and contaminant transport rates to this receptor remain a concern. This is particularly important in the context of mine operations and closure, where dynamic changes in hydraulic gradients (e.g., due to pit dewatering and subsequent rebound) are expected to alter groundwater flow directions and velocities, potentially modifying hydraulic connections to nearby receptors.

ECCC is of the view that monitoring wells should be installed between the historical south MRSA and Farley Lake to directly assess groundwater gradients, flow directions, and seepage from the south MRSA toward the lake especially at closure and post closure.

DFO notes that the proponent has provided ecological rationale for why flow decreases in Farley Creek and downstream watercourses/waterbodies may not cause the harmful alteration of fish habitat. This assessment has increased confidence that the proponent's assertion that the updated effects are within what was assessed in the original environmental assessment. Monitoring to validate these conclusions will be a requirement of the Fisheries Act Authorization.

4.1.3 Analysis and conclusions

IAAC notes that many measures that would mitigate the effects of the Project change were already considered during the original environmental assessment and are described in the current Decision Statement, including the requirement to offset for residual effects to fish and fish habitat (3.1), collect and treat contact water and seepage (3.7), manage acid-generating and metal leaching materials (3.10) and monitor and adaptively manage through follow-up programs for water quality (3.14, 3.17) and water quantity (3.15), and fish and fish habitat (3.16). IAAC is recommending changes to federal conditions within the Decision Statement (see Table 1) to update the definition of the Designated Project (1.7) and Project development areas (1.35) so that these existing conditions apply to the Project change and its adverse federal effects.

IAAC also recommends modifications to the follow-up programs for water quality (3.14), water quantity (3.15), and fish and fish habitat (3.16) to incorporate additional details of the Project change (see Table 1). These adjustments include:

• Adding nitrate, nitrite and ammonia as contaminants of potential concern to be monitored as part of the existing surface water quality follow-up program describe in condition 3.14.2.
• Replacing monitoring water quality in reference lake, Arbor Lake with Carr Lake, since Arbor Lake is much larger than the nearby lakes (Minton, Payne) in conditions 3.14.2 and 3.15.1.
• Removing the requirement of monitoring in the new diversion channel, since the diversion channel will no longer be required, in conditions 3.16.1, 3.16.2 and 3.16.4.

Overall, IAAC is of the view that the proposed project changes would not change the significance of the project's effects on fish and fish habitat, if the Decision Statement is amended to reflect the changes recommended above.

4.2 Health of Indigenous Peoples

4.2.1 Proponent's assessment

The proponent predicts that the proposed changes to the Gordon Site do not result in new or substantially different adverse effects on the health of Indigenous peoples compared to those assessed in the original environmental assessment. Potential health pathways considered by the proponent include exposure through air quality, surface water quality, country foods consumption, and noise or other project-related disturbances, all of which were previously assessed and are addressed through existing mitigation and follow-up measures.

Updated air quality modelling indicates that predicted concentrations of key contaminants generally remain within applicable human health-based guidelines at locations relevant to Indigenous receptors engaged in Traditional Land Use activities. Although localized and infrequent exceedances of short-term air quality criteria (e.g., nitrogen dioxide and particulate matter) are predicted at a limited number of receptor locations, the proponent concludes that these do not represent meaningful changes in health risk relative to the original environmental assessment, and are not expected to result in adverse health effects beyond potential short-term, transient responses in sensitive individuals.

With respect to surface water quality and country foods, the proponent indicates that the pathways of potential exposure for Indigenous peoples, particularly through consumption of fish and other country foods, remain unchanged from those considered in the environmental impact statement. The proponent acknowledges uncertainties associated with modelling surface water quality and bioaccumulation, but states that these uncertainties are consistent with those previously identified and addressed through conservative assumptions. The proponent concludes that no new exposure pathways or materially different cumulative health risks have been introduced as a result of the proposed changes.

The proponent emphasizes that monitoring and adaptive management are central to managing potential cumulative health risks, including risks relevant to Indigenous Nations. The proponent commits to continued air quality monitoring for parameters relevant to human health (e.g., nitrogen dioxide, particulate matter, dustfall), including during periods of peak activity, with adaptive mitigation measures to be implemented if monitoring identifies elevated levels or emerging concerns.

The proponent also indicates that a country foods monitoring program will be implemented to assess metal concentrations in foods that may be consumed by Indigenous peoples, including fish from fish-bearing waters, as well as terrestrial foods such as berries, plants, and harvested wildlife. This program is intended to integrate results from surface water and aquatic monitoring and to assess both Project-related and cumulative changes over time.

Overall, the proponent concludes that the proposed changes to the Gordon Site do not alter the conclusions of the original environmental assessment with respect to the health of Indigenous peoples, and that existing mitigation measures, monitoring programs, and follow-up requirements remain sufficient to manage potential health effects associated with the amended project.

4.2.2 Views expressed

ECCC and Health Canada (HC) acknowledge that the proposed changes to the Gordon and MacLellan sites are expected to result in incremental increases in residual effects on air quality and surface water quality, which are relevant pathways for potential impacts on Indigenous health. ECCC identifies uncertainties related to the timing and magnitude of peak air quality effects—particularly with respect to nitrogen dioxide (NO₂) emissions associated with ore haulage—and recommends revisions to condition 6.3.5 to ensure monitoring is conducted during the period of highest emissions, potentially earlier than currently anticipated, to better verify predictions and support adaptive management. HC similarly emphasizes that increased project production may elevate exposures to contaminants of potential concern, noting that cumulative health risks remain uncertain and warrant careful attention, particularly during peak years of operation when emissions and discharges are expected to be greatest.

Overall, ECCC and HC do not explicitly conclude that significant adverse health effects will occur; however, they stress that the predicted increases in residual effects introduce uncertainty and reinforce the need for strengthened monitoring requirements, early verification of model predictions, and responsive management to protect Indigenous health.

4.2.3 Analysis and conclusions

IAAC considers that the primary pathway by which the proposed changes could affect health of Indigenous Peoples is through changes to air quality. Existing mitigation measures under Condition 6.1, including requirements to control dust and fugitive particulates, and monitoring and adaptive management requirements under Condition 6.3, already address key contaminants such as NO₂ and PM₁₀. Condition 6.3.5 requires monitoring of ambient NO₂ concentrations between November and January during year 4 of operation, or whichever year corresponds to the highest truck traffic volume for ore haulage from the Gordon Site to the MacLellan processing plant, thereby ensuring that monitoring aligns with peak emissions.

IAAC is of the view that, by implementing conditions 6.1 and 6.3 of the Decision Statement, the proposed changes impact to air quality would not alter the significance of the Project's effects on the health of Indigenous Peoples.

5. Conclusion

Based on the information provided by the proponent and the parties consulted, IAAC is of the view that the proposed changes to the Project are not likely to cause significant adverse environmental effects beyond those described in the 2023 environmental assessment report. This conclusion takes into account the mitigation measures and follow-up programs included in the conditions of the Decision Statement, as well as the proposed amendments below.

IAAC recommends updating the Description of the Designated Project to reflect the Project changes, and adding a new schedule (Annex I) to the Decision Statement to consolidate the project description and align with current practices. IAAC also recommends amending conditions 1.7 and 1.35 to update the definitions of the Designated Project and project development area to reference this new schedule.

Finally, IAAC recommends amending:

• condition 3.14.2 to include nitrate, nitrite and ammonia as contaminants of potential concern to be monitored as part of the existing surface water quality follow-up program;
• conditions 3.14.2 and 3.15.1 to replace Arbor Lake with Carr Lake; and,
• conditions 3.16.1, 3.16.2 and 3.16.4 to remove the new diversion channel as a monitoring location.

Annex I: Schedule 1 - Description of the Designated Project

Project overview

The Designated Project is the construction, operation, decommissioning, and reclamation of two open pit gold mines and new metal mill located approximately 1000 kilometres north of Winnipeg, near the Town of Lynn Lake, Manitoba (Figure 1).

The Designated Project will involve the redevelopment of two historical gold mines (the Gordon Site and MacLellan site) and have an ore input capacity of approximately 8,250 tonnes per day, with a planned mine life of approximately 17 years. The Designated Project Area is estimated to cover approximately 12.05 km² and is divided into 3 sections, the Gordon Mine Site Area, the MacLellan Mine Site Area, and the Mine Access Areas (Figure 1).

Gordon Mine Site Area

The Gordon mine site area, shown on Figure 1-B, includes the following components and associated activities:

• open pit;
• ore stockpiles;
• topsoil and overburden stockpile;
• mine rock storage area;
• stockpile borrow source;
• haul and service roads;
• water management, erosion and sediment control structures, and contact water treatment structures, including ditches, sumps, interceptor wells and collection ponds;
• effluent discharge pipeline connecting the collection ponds and sumps (effluent) to the effluent discharge points releasing water meeting regulatory guidelines to Farley Lake and Gordon Lake;
• Wendy pit and East pit temporary discharge line running from the Wendy and East pits to the Hughes River for pit dewatering, removed following completion of dewatering (construction phase;
• freshwater intake pipeline and distribution system;
• on-site generator and electrical distribution system;
• facility area;
• meteorological and other environmental monitoring equipment;
• communication tower; and,
• fuel storage.

MacLellan Mine Site Area

The MacLellan Mine Site Area, shown on Figure 1-A, includes the following components and associated activities:

• open pit;
• satellite pit;
• ore stockpile;
• topsoil, overburden and non-acid generating stockpiles;
• mine rock storage area;
• original equipment manufacturer (OEM) platform;
• ore processing facilities;
• explosive manufacturing and storage;
• tailings management facility for the disposal of tailings that features lined embankments;
• tailings management infrastructure, including pipelines and distribution system;
• water management, seepage, erosion and sediment control structures, and contact water treatment structures, including ditches, sumps, hydraulic barriers, interceptor wells; pumping station; and collection ponds;
• water pumping station connecting freshwater intake from Keewatin River to the water treatment plant and other facilities as required;
• effluent discharge pipelines connecting the collection ponds and sumps (effluent) to the effluent discharge points releasing water meeting regulatory guidelines to the Keewatin River;
• workers camp and supporting infrastructure, with a total capacity of approximately 600 workers during construction and operation;
• haul and service roads;
• on-site electrical distribution system;
• communication tower;
• facilities areas and offices;
• fuel storage; and,
• water and sewage treatment facilities.

Mine Access Area

The Mine Access Area, shown on Figure 1, includes the following components and associated activities:

• mine Access Road that connects each Mine Site Area to the existing regional road (PR 391);
• transmission line that connects the MacLellan Mine Site Area to the regional electrical grid and supporting infrastructure;
• core storage area;
• meteorological and other environmental equipment; and
• laydown areas.

Figure 1 - Text Version

Map showing Lynn Lake Gold Project development area with two inset maps highlighting MacLellan Mine Site Area in blue and Gordon Mine Site Area in orange. Legend includes mine access areas, tailings management facility, and inset map location, with an overview map marking project location in Manitoba near Saskatchewan borders.