NIRB Hearings

Cumberland Resources Ltd Meadowbank Gold Project:

NRCan

Technical Review of the FEIS

March 27-31, 2006

• To help shape the contributions of the resources sector to the Canadian economy, society and the environment

• To promote the sustainable development and use of natural resources

NRCan Mandate:

NRCan Key Services:

• Ensure that federal policies and regulations enhance the natural resource sector’s contribution to the economy

• Ensure that these policies and regulations protect the environment, health and safety of Canadians

• Conduct leading-edge science and develop technologies that help Canadians understand their land mass and use their resources wisely

NRCan’s Areas of Expertise:

• Geohazards (earthquakes, landslides)

• Geoscience (hydrogeology, surficial and bedrock geology)

• Permafrost

• Mine site development, mineral processing technology, and mine reclamation

• Mine waste management, including tailings and waste rock, protection of surface and groundwater quality, and acid mine drainage

• Explosives (manufacture and storage thereof)

• Geoscience, geohazards, geotechnics and permafrost

• Mine waste management

• Explosives

NRCan’s technical reviews were conducted by :

The October 2005 FEIS was reviewed by scientistswith expertise in:

• Geological Survey of Canada, Earth Sciences Sector• Explosives Regulatory Division, Minerals and Metals

Sector• Mining and Mineral Sciences Laboratories, Minerals and

Metals Sector

NRCan’s technical review focuses on 4 of the key topics identified by NIRB:

• Project Alternatives• Water Quality• Permafrost• Other Issues

General Comments

• NRCan commends the Proponent for efforts towards addressing outstanding issues identified by NIRB.

• NRCan considers that the majority of its issues and concerns from the draft EIS review have been resolved.

• Comments and recommendations related to NRCan’s remaining issues are submitted for consideration by NIRB and the Proponent.

• NRCan acknowledges the Proponent’s efforts to resolve NRCan’s remaining issues in advance of this hearing.

Effect of Blasting Residues on Water Quality

• The FEIS has differing takes on the type of explosives to be used. In some parts ammonium nitrate fuel oil (ANFO) is mentioned; in others the use of emulsion blends is discussed.

• There is a considerable (5 to 15%) loss of ammonia and nitrates associated with the use of ANFO.

• The Proponent’s predicted ammonia and nitrate loadings to receiving lakes do not correspond with expected loadings resulting from the stated ANFO use.

• No significant impact on water quality from blasting residues.• Ammonia and nitrate loadings to be minimized by a judicious

choice of explosive.

Proponent’s conclusion

NRCan’s conclusion

NRCan’s recommendation

Effect of Blasting Residues on Water Quality

• The Proponent should commit to use an explosive with water resistance, emulsion or emulsion blend; or else reassess ammonia and nitrate loadings based on the use of ANFO and subsequent effects on water quality in receiving water bodies.

Resolution

• The Proponent indicated in an email to NRCan dated March 23, 2006, that it intends to use emulsion blend for pit blasting to minimize residual ammonia and nitrates.

Other Issues:Acid Rock Drainage and Leaching of Metals and Other Constituents

• The Proponent has sufficiently characterized the mine waste materials with emphasis on generation of acid rock drainage (ARD) and leaching of metals and non-metal constituents.

NRCan’s conclusions

Other Issues:Acid Rock Drainage and Leaching of Metals and Other Constituents

NRCan’s recommendations

• As mining progresses, the prediction results presented in the FEIS should be confirmed and waste management plans should be re-evaluated if necessary.

• The feasibility of segregating and stockpiling of various rock types for blending, co-disposal and placement as cover materials should be evaluated. During operations, proposed disposal practices should be re-evaluated by systematic sampling of waste rock and tailings.

• Preventive and control measures should be developed to manage the tailings during operations and following closure.

• As freezing of the tailings progresses, it is likely that concentrated pore fluids will be forced ahead of the freezing front.

• The Project Alternatives report (Fig. 7.6) shows the dam and its foundation completely frozen. However, this final state may take several decades to achieve.

• The report “Thermal Modelling of the Tailings Deposit in the Second Portage Lake, Meadowbank Gold Project” indicates that freezing of the tailings will not be complete by the time Second Portage Lake is returned to its original level.

Proponent’s conclusion

NRCan’s conclusion

Tailings Thermal ModelingFreeze-back of the Meadowbank Tailings

As the tailings freeze (dashed blue line), remaining unfrozen pore water with contaminants will be forced into Second Portage Lake before the tailings dam and underlying bedrock is frozen.

Tailings Thermal ModelingFreeze-back of the Meadowbank Tailings

Tailings Thermal ModelingFreeze-back of the Meadowbank Tailings

NRCan’s recommendations

• The Proponent should demonstrate that tailings freeze-back will not result in discharge of contamination to Second Portage Lake.

• The Proponent should provide an indication of the expected life of the tailings dam.

Tailings Thermal Modeling Effects of Groundwater Flow

Proponent’s conclusions• Tailings will freeze over completely within 200-300 years and effects of regional

groundwater flow on the freeze-over time are minimal. • Tailings porewater is unlikely to impact the deep groundwater regime.

NRCan’s conclusions• The tailings thermal modeling did not adequately consider advective heat

transport to the tailings from ground water upwelling in the Second Portage Fault that may inhibit tailings freeze-back during early stages of mining

• The tailings seepage modeling did not consider preferential flow of tailings porewater back into the Second Portage fault before freeze-back is complete

• Until tailings are completely frozen, contaminated groundwater from the impoundment may migrate toward the Portage pit lake through the fault or the bedrock beneath the dam.

Tailings Thermal Modeling Effects of Groundwater Flow

NRCan’s recommendations

• The Proponent should conduct supplementary technical analyses that specifically investigate effects of groundwater flow and advective heat transport in the Second Portage fault on tailings freeze-over and on possible migration of contaminants toward the pit lake.

• The Proponent should install deep monitoring wells in the

tailings dike to sample groundwater quality and hydraulic gradients in the Second Portage fault during operations and the post-closure period.

Tailings CharacterizationUltramafic Rock as Cover Material

• The Proponent claims that ultramafic (UM) capping material will have a low permeability to infiltration yet will be coarse enough to allow convective air cooling of tailings and waste rock during the winter.

Proponent’s conclusion

NRCan’s conclusion

• The Proponent’s statement appears contradictory and that raises doubts about the ability of the UM cover to perform as intended, maintaining a thaw depth above the top of the tailings.

NRCan’s recommendations

Tailings CharacterizationUltramafic Rock as Cover Material

Resolution• In a conference call with NRCan on March 23, 2006, the

Proponent committed to providing a written clarification of the UM capping scheme for the public record.

• The Proponent should document the permeability to air and to water of the proposed UM capping layer• The Proponent should demonstrate quantitatively that the capping layer will perform as planned and maintain the seasonal thaw depth above the top of the tailings

Other Issues:Geoscience, geohazards and geotechnical

NRCan’s recommendations

• NRCan requests minor points of clarification regarding the character of principal faults in the mine site area and the potential for fault reactivation in the case of a seismic event.

• NRCan is satisfied with the Proponent’s responses to previously raised concerns regarding the deep groundwater flow regime; quantity and quality of pit inflows; stratification and trophic status of the pit lakes; lake sediments; nature and composition of the bedrock and overburden; borrow pits and quarries for all-season road; and, earthquakes and seismic hazards.