Section Synopsis
Pages: 107-108The provided text describes the geological characteristics of the Revell batholith, the proposed site for a Deep Geological Repository (DGR) for Canada’s used nuclear fuel. It details the surface bedrock geology, consisting of 11 identified units, and the deep geology confirmed through 3D modeling and six boreholes reaching depths of up to 1 km. The proponent asserts that the site offers a sufficient volume of homogeneous, competent granitoid rock at the target depth of 750 m, positioned between inferred fracture zones. The batholith is characterized as a 2.7-billion-year-old stable formation with thin overburden, except in localized wetland areas.
Community Assessment Narrative
The geological description provided by the NWMO presents a highly optimistic view of the Revell batholith's suitability for a Deep Geological Repository. While the technical data regarding bedrock units and age is well-documented, the narrative relies heavily on the assumption that surface-level homogeneity is a reliable proxy for deep-subsurface stability. The text frequently uses qualifying language such as 'potentially suitable' and 'presently inferred,' which introduces a degree of uncertainty that is not fully explored in the subsequent claims of 'sufficient volume' and 'competent rock.' This creates a tension between the cautious scientific terminology and the definitive conclusions drawn about the site's viability.
Furthermore, the reliance on only six boreholes to characterize a rock unit of 40 km by 15 km raises questions about the statistical representativeness of the data. The mention of 'larger-scale structures presently inferred to be fracture zones' is a critical point of concern; the text suggests the repository can simply be 'positioned between' these zones, but it lacks a discussion on the connectivity of these fractures or their potential for hydraulic conductivity. From a transparency perspective, the document would benefit from a more rigorous acknowledgment of the limitations of 3D geophysical modeling and the potential for encountering unforeseen heterogeneities at the 750 m level. The tone is professional but leans toward a confirmatory bias, emphasizing the 'good bedrock exposure' while downplaying the complexities of the 'several metres' of overburden in sensitive wetland areas.
Corrective Measures & Recommendations
To improve the technical rigor of the submission, the proponent should implement a high-density borehole drilling program and advanced seismic reflection surveys. This is necessary to transition from 'inferred' fracture zones to a verified structural map. Understanding the precise geometry and connectivity of these fractures is vital, as they represent the primary pathways for potential radionuclide migration. A detailed hydrogeological characterization of these zones should be prioritized to justify the claim that the repository can be safely isolated from the surrounding environment.
Additionally, the proponent must provide a more comprehensive analysis of the overburden in valleys and wetland areas. Given that these areas show significantly thicker overburden, the potential for localized groundwater recharge and its impact on the underlying bedrock stability must be addressed. The proponent should also include a sensitivity analysis of the 3D geophysical model to demonstrate how variations in rock density or undetected minor faulting could alter the current 'homogeneous' interpretation. This would enhance the transparency of the assessment and provide the regulatory body with a clearer understanding of the geological risks.
On 16 February, 2026 the Impact Assessment Agency of Canada (IAAC), with input from the Canadian Nuclear Safety Commission (CNSC), published a Summary of Issues (SOI) for the proposed Deep Geological Repository (DGR) for Canada’s Used Nuclear Fuel Project, put forward by the Nuclear Waste Management Organization (NWMO). The SOI identifies the key issues that IAAC considers relevant to the federal integrated impact assessment process for the project. NWMO’s response to the SOI will assist IAAC in determining whether an impact assessment is required under section 16 of the Impact Assessment Act. If an impact assessment is required, the issues outlined in the SOI—together with NWMO’s response—will help shape the scope of the assessment and inform the continued development and finalization of the Integrated Tailored Impact Statement Guidelines and associated plans.
Alignments to IAAC Summary (SOI)
The technical findings provided by Melgund Township demonstrate a high degree of alignment with the "Geology, geochemistry, and geological hazards" theme within the IAAC Summary of Issues (SOI). Specifically, the community’s concern regarding the "presently inferred" nature of structural features and fracture zones directly supports the IAAC’s identified need for a "detailed understanding of the rock formation... based on its geological characteristics (e.g., rock type, permeability, structural stability, presence of faults and fractures)." While the IAAC document flags the broad requirement for suitability, the community assessment provides the necessary technical specificity by identifying that the current reliance on only six boreholes for a 40km x 15km batholith is insufficient to meet the Agency's requirement for a "detailed understanding."
Furthermore, the community’s observations regarding the "inferred" thickness of overburden in wetlands and valleys align with the IAAC’s concerns under "Groundwater and Surface Water" and "Terrestrial, riparian and wetland environments." The community’s warning that thicker overburden could increase the risk of surface-to-subsurface water interaction validates the IAAC’s focus on "hydrological regimes" and "potential radiological effects to water." There is a notable gap where the community assessment has identified a specific technical vulnerability—the reliance on geophysical modeling over direct physical evidence for the base of the batholith—which provides a concrete example of the "high uncertainty" and "unanticipated problems" flagged by the IAAC under the "Accidents and Malfunctions" section.
The community’s call for a sensitivity analysis of the 3D geophysical model also aligns with the IAAC’s interest in "Alternative means" and "Project description" transparency. By highlighting that the proponent’s "homogeneous" interpretation of the rock could be altered by undetected minor faulting, the community is providing the evidentiary basis for the IAAC’s concern regarding the "adequacy, clarity, and transparency of the Project Description." Essentially, the community findings serve to validate the IAAC’s broad categories of concern with site-specific, technical evidence that demands a more rigorous data-collection phase from the proponent.
Recommendations
The working group recommendations focus on transitioning the project’s geological baseline from "inferred" assumptions to "verified" physical data. It is recommended that the proponent implement a high-density borehole drilling program and advanced seismic reflection surveys to create a verified structural map of the Revell batholith. These actions are essential to addressing the IAAC’s requirement for a "detailed understanding of the rock formation" and to ensure that the "structural stability" and "presence of faults" are not merely modeled, but physically confirmed. This direct evidence is the only way to satisfy the concerns raised in the SOI regarding the long-term containment suitability of the host rock.
Additionally, the working group recommends a prioritized hydrogeological characterization of fracture zones and a site-specific geotechnical drilling program in wetland areas. These recommendations are designed to address the alignments found in the IAAC’s "Groundwater and Surface Water" and "Radiological contamination of water" sections. By determining the exact geometry and connectivity of fractures and the precise depth of overburden, the proponent can provide the "transparency in reporting" and "clearer understanding of geological risks" that the IAAC SOI demands. These steps are necessary to mitigate the "high uncertainty" currently associated with the project’s reliance on 3D geophysical models.
Key Claims
Underlying Assumptions
Critical Observations & Gaps
Analysis Table| Issue Identified | Implication | Information Required |
|---|---|---|
| The structural features are 'presently inferred' rather than fully characterized. | Inferred fracture zones (FZs) represent the highest risk for containment failure; 'positioning between' them assumes they are not part of a larger, interconnected network. | Detailed fracture network modeling and hydraulic testing of the identified FZs. |
| Overburden in valleys and wetlands is 'inferred to be several metres thick' without specific measurements. | Thicker overburden in wetlands could complicate construction and increase the risk of surface-to-subsurface water interaction. | Site-specific geotechnical drilling in wetland areas to determine exact overburden depth and composition. |
| Low borehole density for a project of this magnitude. | Six boreholes for a 40km x 15km batholith may not capture localized geological anomalies that could disqualify specific repository locations. | A commitment to a multi-phase drilling program to increase data density before final site selection. |
| Reliance on geophysical modeling over direct physical evidence for the base of the batholith. | The 3D model is the basis for the '3 km thick' claim, but models are only as good as their input data. | Validation of the 3D model through deep-crustal seismic surveys. |
Working Group Recommendations
Require site-specific geotechnical drilling and sampling in the 'valleys and wetland areas' where overburden is currently only 'inferred to be several metres thick' to establish precise depth and composition data.
Challenge the statistical sufficiency of using only six deep boreholes to characterize the entire 40km x 15km Revell batholith as 'homogeneous' and request a justification for this sampling density.
Request immediate validation and direct mapping of the 'larger-scale structures presently inferred to be fracture zones (FZs)' referenced in the Deep Geology section, moving beyond 'inference' to physical characterization.
Understanding the Impacts of Nuclear Waste on our Community
This digital archive houses the public comments submitted to the Impact Assessment Agency of Canada regarding Project 88774: The Nuclear Waste Management Organization Deep Geological Repository (DGR) for Canada's Used Nuclear Fuel Project. The impact assessment is led jointly by the Impact Assessment Agency of Canada and the Canadian Nuclear Safety Commission. This archive preserves community perspectives, concerns, and observations shared during the assessment process, particularly in relation to Melgund Township, Northwestern Ontario and the communities of Dyment and Borups Corners who are the closest and most impacted of all in the process.