Section Synopsis
Pages: 112-113The provided text outlines the geochemical characterization of rock core samples at the Revell site to assess the potential for acid rock drainage (ARD) and metal leaching (ML). Based on data from six boreholes and surface mapping, the NWMO identifies the bedrock as 95% granodiorite-tonalite, characterized by low porosity and minimal sulfur-bearing minerals. Preliminary findings suggest the rock is non-acid generating and non-toxic, which is expected to support radionuclide retardation and the durability of the engineered barrier system. Further kinetic testing, leachate analysis, and studies on overburden and construction materials are planned to verify these initial conclusions for regulatory licensing.
Community Assessment Narrative
The geochemical assessment presented in the text exhibits a high degree of technical confidence, yet it relies heavily on preliminary data and internal NWMO documentation. While the use of the Mine Environment Neutral Drainage (MEND) framework provides a recognized methodological basis, the conclusion that the rock is 'not anticipated' to be acid-generating or possess metal-leaching potential is made while kinetic testing is still underway. This suggests a potential confirmation bias, where the proponent anticipates a favorable outcome before the scientific process is complete. The reliance on only six boreholes to characterize the lithological homogeneity of a site intended for a deep geological repository raises questions about the statistical representativeness of the sampling, particularly regarding the 5% of 'subordinate rock types' like amphibolite and felsic dykes which may possess different geochemical profiles.
Furthermore, the text links low porosity directly to the retardation of radionuclide movement without discussing the potential for fracture-controlled flow, which is a common feature in crystalline rock environments. The tone is generally professional but leans toward a 'favourable' narrative, emphasizing the durability of the copper barriers and the non-toxic nature of the rock. Transparency could be improved by providing more specific data from the ongoing kinetic tests rather than relying on qualitative predictions. The transition from preliminary findings to planned work acknowledges the need for more data, yet the document's current state leaves gaps regarding the variability of the rock and the specific impacts of the 'subordinate' lithologies on long-term environmental safety.
Corrective Measures & Recommendations
The proponent should complete and publish the results of the kinetic geochemical testing before finalizing the impact assessment. Relying on 'anticipated' results for acid rock drainage and metal leaching potential introduces regulatory risk and may undermine public trust. It is recommended that the proponent provide a detailed sensitivity analysis of the 5% subordinate rock types (amphibolite and dykes) to ensure that localized concentrations of sulfur-bearing minerals or metals do not exist in quantities that could impact the repository's integrity or surface water quality upon excavation.
Additionally, the proponent should expand the geochemical baseline to include a broader spatial distribution of boreholes beyond the initial six to confirm the lithological homogeneity claimed. To improve transparency, the 'Confidence in Safety' reports and other internal NWMO citations should be made easily accessible to the public and independent reviewers. Future submissions should also clarify how the measured 'connected porosity' relates to macro-scale fracture networks, as these features are often more critical for radionuclide transport than the matrix porosity of the rock core samples themselves.
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 from Melgund Township demonstrate a high degree of alignment with the "Physical and Biological Environment" section of the IAAC Summary of Issues (SOI), specifically regarding the "Geochemical behaviour of rock material" and the "Suitability of host rock for long-term containment." The IAAC SOI explicitly flags concerns about acid rock drainage (ARD) and metal leaching (ML) from excavated rock. Melgund’s analysis validates this concern by identifying a significant procedural gap: the proponent has made definitive claims that the rock is non-acid generating while kinetic testing—the primary method for verifying long-term leaching behavior—is still listed as "underway." This discrepancy suggests that the proponent’s current conclusions may be premature and lack the rigorous evidentiary basis required by the IAAC process.
Furthermore, Melgund’s observations regarding "secondary porosity" and "fracture networks" directly support the IAAC’s requirement for a detailed understanding of "permeability" and the "presence of faults and fractures" (SOI Section: Geology, geochemistry, and geological hazards). While the proponent’s submission focuses on matrix porosity, Melgund’s assessment correctly identifies that radionuclide transport is more likely to occur through macro-scale fractures. This represents a critical technical gap; if the proponent does not account for these fracture networks, their safety case for long-term containment may be based on misleading data, failing to meet the IAAC’s criteria for a "detailed understanding of the rock formation."
There is also a strong alignment regarding transparency and data integrity. The IAAC SOI (Annex A: Project Description) notes public concerns regarding the "adequacy, clarity, and transparency" of the proponent’s information. Melgund’s finding that the proponent relies heavily on internal NWMO (2023) documents rather than independent, peer-reviewed studies highlights a specific barrier to transparency. By citing internal reports that are not readily accessible, the proponent limits the ability of the community and the Agency to verify claims regarding rock toxicity and mineralogy, thereby validating the IAAC’s broader concern about the characterization of uncertainty and risk.
Recommendations
The community working group recommends that the proponent be required to complete and publish all kinetic geochemical testing results prior to the finalization of the Impact Assessment. This is essential to address the IAAC’s identified concerns regarding ARD/ML and to ensure that the environmental baseline is not based on "anticipated" or "preliminary" data. To further align with the IAAC’s focus on geological suitability, the proponent should conduct a detailed sensitivity analysis on the 5% subordinate rock types, such as amphibolite and dykes. This analysis is necessary to ensure that localized concentrations of sulfur-bearing minerals do not pose a risk to water quality or repository integrity that was missed due to the current limited sampling size of only six boreholes.
To address the gaps in transparency and technical scope, it is recommended that the proponent provide a clear justification for the statistical significance of their current sample size relative to the total volume of the proposed excavation. The working group also recommends that the proponent transition from a focus on matrix porosity to a comprehensive model of macro-scale fracture networks and hydraulic conductivity. Finally, to satisfy the IAAC’s requirements for transparency, all internal "Confidence in Safety" reports and cited geochemical data must be made available for independent peer review. These steps are vital to resolving the uncertainties identified in the Summary of Issues and to building the necessary public trust in the technical safety of the Revell site.
Key Claims
Underlying Assumptions
Critical Observations & Gaps
Analysis Table| Issue Identified | Implication | Information Required |
|---|---|---|
| Characterization of the site relies on only six boreholes and 100 core samples. | Small sample sizes may miss localized geochemical hazards that could affect water quality or barrier integrity. | A justification for the statistical significance of the sample size relative to the total volume of excavated rock. |
| Definitive statements about ARD/ML potential are made while kinetic testing is still 'underway'. | Drawing conclusions before kinetic testing is finished may lead to underestimating long-term metal leaching. | Full disclosure of kinetic testing parameters and interim data. |
| Frequent citations of internal NWMO (2023) documents rather than peer-reviewed or independent studies. | Heavy reliance on internal reports limits the ability of external reviewers to verify the claims. | Provision of the cited internal reports for public and regulatory review. |
| The text focuses on matrix porosity but does not address secondary porosity or fracture networks. | If radionuclides move primarily through fractures, the matrix porosity data provided may be misleading regarding safety. | Data on hydraulic conductivity and fracture mineralogy. |
Working Group Recommendations
Require the submission of completed kinetic testing and leachate analysis results prior to the Impact Statement, rather than accepting the 'anticipated' non-acid generating outcomes cited in the text.
Mandate the immediate inclusion of 'overburden' and 'construction materials' in the geochemical baseline testing program to establish background salinity and metal levels.
Challenge the reliance on 'matrix porosity' (0.45%) as the primary indicator for radionuclide retardation and request the inclusion of fracture network hydraulic conductivity as a specific Valued Component indicator.
Request a statistical justification for the sufficiency of six boreholes to characterize the geochemical homogeneity of the entire repository volume, specifically regarding the 5% subordinate rock types (amphibolite and dykes).
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.