Re: Information Request Submission for the NIRB s Review of AEM s Whale Tail Pit Expansion Project Proposal

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1 February 21, 2019 NIRB file # - 16MN056 NRCan # - NT- 099 Sophia Granchinho Manager, Impact Assessment Nunavut Impact Review Board PO Box 1360 Cambridge Bay, NU, X0B 0C0 Via electronic mail to: info@nirb.ca Dear Ms. Granchinho, Re: Information Request Submission for the NIRB s Review of AEM s Whale Tail Pit Expansion Project Proposal Natural Resources Canada (NRCan) is participating in the review of the Whale Tail Pit Expansion Project Proposal under the Nunavut Planning and Project Assessment Act. In response to your letter of January 10, 2019, NRCan has reviewed the Whale Tail Pit Final Environmental Impact Statement Addendum submission. NRCan has identified 11 information requests in the areas of permafrost, terrain stability, and hydrogeology for the NIRB s consideration. NRCan appreciates this opportunity to comment on the application. Should you have any questions related to NRCan s review, please do not hesitate to contact me at peter.unger@canada.ca. Sincerely, Peter Unger Senior Environmental Assessment Officer/Agent prinicipal d évaluation environnementale Office of the Chief Scientist/ Bureau du scientifique principale Natural Resources Canada / Ressources naturelles Canada peter.unger@canada.ca 588 Booth Street, Ottawa, Ontario, K1A 0Y7

2 Natural Resources Canada s (NRCan) Information Requests Agnico Eagle Mines Limited s Whale Tail Pit Expansion Project (16MN056) 1.0 Permafrost and Terrain Stability Documents Reviewed Project Description FEIS Addendum: Chapters 1, 2, 3, 5 (Terrain, Permafrost, Soils), 6 (sections relevant to groundwater), 8. Relevant Appendices: Vol. 1, 1-B, 1-D; Vol. 3, 3-D; Vol.5, 5-A; Vol.6, 6-A, 6-B; Vol. 8, 8-A, 8-B Information Requests IR Number(s): 1, 2 Subject: Baseline data on terrain and permafrost conditions Reference: FEIS Addendum (Secs , 1.2.5, 5.3.2, 5.3.6); Vol. 5, App. 5-A Information on terrain and permafrost conditions is essential to adequately design project components to ensure that they perform as intended. In particular, knowledge of ground ice conditions is required to assess terrain stability and determine if thawing of permafrost due to project activities (surface disturbance, impoundment of water), will have an impact on ground stability and performance of structures such as those required for water management (e.g. dams and dikes). Terrain mapping has been done for the project area including the area surrounding the proposed expanded Whale Tail pit, IVR pit, and underground mining operations (Vol. 5, App. 5-A, Figs. C-18, C-19, C-21, C-22). However, there does not appear to be much detailed information on permafrost conditions including ground ice content beyond references to national scale maps (e.g. Heginbottom et al. 1995; Brown et al. 1998) which are not appropriate for assessments of conditions at a local scale. The Proponent has indicated that a key uncertainty is the thickness of the active layer and the ground ice content (FEIS Addendum, Sec ) NRCan realizes that detailed site investigations are usually done to support detailed engineering. However, NRCan would like clarification on any field investigations such as geotechnical boreholes that have been done to support design of project facilities such as water management structures, underground operations, and the waste rock storage facility. Information is also required on how the Proponent plans to address uncertainties with respect to permafrost such as active layer thickness and ground ice conditions NRCan IR#1: Please provide clarification on field investigations (including geotechnical borehole drilling) conducted to provide detailed information on permafrost conditions such as ground ice content to support design of project components NRCan IR#2: Please also provide information on plans to address uncertainties with respect to active layer thickness and ground ice conditions to support final design of project components

3 IR Number(s): 3,4 Subject: Baseline soils Reference: FEIS Addendum (Sec ); Vol. 5, App. 5-A The proponent recognizes that existing information on soil types, characteristics, and distribution in the region is limited, and consequently mapped an additional ha to incorporate the road the road corridors to Lake D1 and Lake D5, and the quarries along the haul road (FEIS Addendum, Sec ). The properties of each surficial material crossed by the haul road are described in detail in The Terrain, Permafrost, and Soils Baseline Report (Vol. 5, App. 5-A) of the Approved Project FEIS submission, but it is not clear where maps are presented in the Addendum for the additional ha mapped that covers the road corridors to Lake D1 and Lake D5 within the expanded LSA. NRCan IR#3: Please provide any information on detailed soil mapping conducted that covers the road corridors to Lake D1 and Lake D5 within the expanded LSA. IR Number(s): 4,5 Subject: Permafrost and talik distribution Reference: FEIS Addendum ( ); Vol. 6, App. 6-A; Vol. 8, App. 8-A.1) Permafrost can provide an impermeable barrier to groundwater flow and limit connections between surface and subsurface water. Unfrozen zones or taliks can exist beneath large water bodies that do not freeze to the bed in winter. If lakes are larger than a critical size, an open talik will exist providing a hydrologic connection between surface and groundwater. The Proponent has indicated that after 11 years of closure, the base of the Whale Tail Pit Lake is predicted to be hydraulically connected to the deeper groundwater flow system, and after 50 years, the permafrost below the full pit footprint is predicted to have completely melted (FEIS Addendum, Sec ; Vol. 6, App. 6-A, Sec. 3.3 ; Vol. 8, App. 8-A.1, Sec. 2.6). The Proponent also indicated that with flooding and formation of IVR Pit Lake during closure that permafrost is also predicted to fully melt the underlying permafrost below the IVR footprint, but that it will take approximately 1000 years (FEIS Addendum. Sec ; Vol. 6, App. 6-A, Sec. 3.3; Vol. 8, App. 8-A.1, Sec. 2.6). IVR Pit and Whale Tail Pit have been treated separately in the analysis, but with flooding upon closure the pits will together form one lake (App. 8-A, 8-A.1, Fig A.8). It is important to know if lateral permafrost thaw will be induced earlier beneath IVR Pit by encroachment of the thaw zone from beneath Whale Tail Pit. Encroachment of the thaw zone may effectively connect the thaw zone beneath IVR Pit to sub-permafrost groundwater much earlier than predicted. NRCan therefore requires clarification on the analysis of thaw zone development between the two pits to complete its technical review. Information Request: NRCan IR#4: Please clarify whether the analysis of thaw under IVR Pit includes consideration of potential lateral effects due to permafrost thaw under Whale Tail Pit.

4 NRCan IR#5: Please provide any related information on thermal analysis conducted to support prediction of permafrost thaw beneath the between IVR Pit and Whale Tail Pit with flooding upon closure. IR Number(s): 6,7 Subject: Design of Waste Rock Storage Facility (WRSF) Reference: FEIS Addendum (Sec ); Vol. 8, App. 8-A, 8-A.1, 8-A.3) The Proponent has indicated that they will take advantage of the cold conditions and have adopted freeze control and climate control strategies for the WRSF (App. 8-A, 8-A.1, Sec. 9). Frozen conditions will be utilized to immobilize pore fluids, control acid mine drainage reactions and prevent potential migration of contaminated pore water outside the storage facility. Part of this strategy involves a cover of non acid generating waste rock of sufficient thickness to provide insulation and prevent thawing of the potentially acid generating rock and therefore maintain frozen conditions over the long-term. The proposed design of the 4.7 m thick NPAG/NML waste rock placement as a final surface cover for Whale Tail and IVR WRSFs is similar to that of the Meadowbank Portage WRSF, and is based on results calibrated to the Meadowbank WRSF thermal data to date and climate change predictions (App. 8-A, 8- A.1, Sec. 9.1). The thermal response in the IVR WRSF is expected to be like the Whale Tail WRSF (App. 8- A, 8-A.3, Sec ). NRCan recognizes that there are currently no thermistors in the footprints of the Whale Tail and IVR WRSF footprints, but that they will be installed progressively in the thermal cap during construction to assess the effectiveness of the 4.7 m cover thickness on isolating the PAG waste rock from the active zone of seasonal freezing and thawing. The Proponent has indicated that they may consider supplemental modelling to evaluate the long-term performance of the rock cover on top of the WRSFs, and would use data from installed thermistor strings for model calibration (App. 8-A, 8-A.3, Sec ). NRCan would like clarification on the specific conditions or circumstances that would require the Proponent to consider supplemental thermal modelling to evaluate the long-term performance of the rock-cover on top of the WRSFs, and whether or not the results from any supplemental modelling would be applied to adjust the rock cover thickness on top of all of the WRSFs or just individual WRSFs on a case-by-case basis. NRCan IR#6: Please clarify the specific conditions or circumstances that would require supplemental modelling to evaluate the long-term performance of the rock cover on top of the WRSFs. NRCan IR#7: Please clarify if supplemental thermal modelling results derived for any WRSF would be used to adjust the rock cover thickness on top of each of the Meadowbank Portage, Whale Tail, and IVR WRSFs, or if the supplemental thermal modelling would be specific to an individual WRSF rock cover thickness and apply only to that particular WRSF. 2.0 Hydrogeology Documents Reviewed MN056-FEIS Addendum Main Document-Pt 4-IA2E.pdf

5 MN056-Vol 6-App 6A-IA2E.pdf MN056-Vol 6-App 6B-Pt 2-IA2E.pdf Information Requests IR Number(s): 8 Reference: MN056-FEIS Addendum Main Document-Pt 4-IA2E.pdf Section 6.4 In Section of the FEIS Addendum Main Document, the proponent states: "Refinement of the model input parameters may affect magnitude of effects on groundwater quantity/quality presented; however, conclusions are expected to remain unaffected." NRCan was unable to verify this statement through the data presented. NRCan IR#8: Please provide data or analysis to substantiate the statement: "Refinement of the model input parameters may affect magnitude of effects on groundwater quantity/quality presented; however, conclusions are expected to remain unaffected." IR Number(s): 9 Reference: MN056-Vol 6-App 6A-IA2E.pdf Figure 3 Figure 3 indicates levels of uncertainty regarding the distribution of hydraulic conductivities (K) with bedrock depth. As shown in this figure, K values diminish with depth. This behaviour usually follows an exponential decay function (Lefebvre et al. 2015). Because models are sensitive to K values with respect to groundwater flows, we recommend that the Proponent test different scenarios of K functions based on the data in Figure 3. This could also contribute to the response to NRCan IR#8. As an example, Janos et al. (2018) presents an exponential decay function log10(kz)=log10(kmin)+(log10(kmax)-log10(kmin))*exp(-a*z) where z is the depth below the top of the bedrock, kz is the hydraulic conductivity at depth z, Kmin is the minimum hydraulic conductivity asymptotically approached by the curve, Kmax is the maximum hydraulic conductivity, and α is a curve decay constant. The decay is adjusted element by element in a vertical direction. References Janos, D., Molson, J., Lefebvre, R., Regional groundwater flow dynamics and residence times in Chaudière-Appalaches, Québec, Canada: Insights from numerical simulations. Canadian Water Resources Journal / Revue canadienne des ressources hydriques 43,

6 Lefebvre, R., J. M. Ballard, M.-A. Carrier, H. Vigneault, C. Beaudry, L. Berthot, G. Légaré-Couture, et al Portrait des ressources en eau souterraine en Chaudière-Appalaches, Québec, Canada (No. Rapport final INRS R-1508). Projet réalisé conjointement par l Institut national de la recherche scientifique (INRS), l Institut de recherche et développement en agroenvironnement (IRDA) et le Regroupement des organismes de bassins versants de la Chaudière-Appalaches (OBV-CA) dans le cadre du Programme d acquisition de connaissances sur les eaux souterraines (PACES). NRCan IR#9: Please provide the effect of a log-linear variation of hydraulic conductivities with depth on modeling results (inflow rates/volumes and flow directions). IR Number(s): 10 Reference: MN056-FEIS Addendum Main Document-Pt 4-IA2E.pdf A complete conceptual model would help to understand groundwater dynamics and their relation to permafrost and surface water. In the report, there is no figure showing a conceptual model that includes the IVR pit. NRCan IR#10: Please provide a complete conceptual model of the Whale Tail and IVR pits at their maximum depths. IR Number(s): 11 Reference: MN056-Vol 6-App 6B-Pt 2-IA2E.pdf The model includes constant head boundary conditions. These boundary conditions induce flux going in or out of the model. Therefore, it is important to validate the magnitude and direction of these fluxes. NRCan IR#11: Please provide equivalent recharge and discharge rates for each feature (lakes, rivers, ) with constant head boundary conditions in a table and on a map.