NRCan’s Expertise

• Geohazards (earthquakes, landslides etc.)

• Geoscience (marine and coastal geology, and landscape processes, groundwater etc.)

• 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 but not use)

Caro’s Acid for Cyanide Destruction

• Preliminary results indicate excellent cyanide and thiocyanate destruction

• Process has not been used often in Canada

• Tocicity is an important consideration as oxidative processes for cyanide destruction tend to generate toxic by-products

• More information (e.g. monitoring) is needed on the toxicity of final solutions

• Status of samples sent to AMEC for further analysis ?

Explosives Manufacture & Storage

Explosives Manufacture & Storage (cont’d)

Explosives Manufacture & Storage (cont’d)

Presentation by Sharon Smith (GSC)

• Acid rock drainage• Baseline climate data• Extraction of borrow resources• Shoreline stability of Tail Lake• Processed ore containment area (Tail L. tailings

impoundment)• Physical marine and coastal processes• Hydrological monitoring• Additional water balance/water quality issues• Monitoring

April 21, 2023

NRCan/Geological Survey of Canada PresentationsPresented by Sharon SmithGeological Survey of Canada

Miramar Hope Bay Ltd. Doris North Project:

NIRB Hearing

July 11 - 13, 2004

Presentation based on technical reviews by the Geological Survey of Canada, Earth Sciences Sector, NRCan:

• Sharon Smith, TSD – Permafrost and geotechnical issues

• John Kerswill, MRD – Deposit geology and acid rock drainage potential

• Steven Solomon, GSC-Atlantic – Physical marine and coastal aspects

• John Adams, GSC-Pacific – Seismic hazards

• Shawna Simpson, TSD – Groundwater/surface water issues

• Margo Burgess, TSD – EA coordinator

• Available information suggests that ore exposed in underground workings, mineralized rock stored in surface piles and tailings have low capacity for generating acid rock drainage– gold deposits low in sulphide minerals– carbonate minerals abundant

• Absence of significant arsenopyrite in ore suggests environmental problems associated with arsenic-rich gold deposits are not a problem at Doris North

Seismic hazards• NRCan confirms the project is located in seismically inactive

region• no assessment of seismic hazards necessary

Acid Rock Drainage Potential

Baseline Climate Data

• Required for thermal modelling and design of infrastructure including tailings impoundment facilities in permafrost environments

• Required to determine water balance for Tail/Doris Lake watershed

Issues• Inadequate data are available for the Doris North site

• Data collected at Boston since 1993 used to represent Doris North

• Data record extended through development of relationships between Boston and MSC weather stations

• Relationships, in particular for precipitation (including snow) and evaporation, are unreliable

• Errors in the water balance could mean Tail Lake will reach maximum capacity sooner than expected

• Errors may result in inadequate design of tailings impoundment facility

MBHL has acknowledged shortcomings of climate data

Recommendations

• NRCan recommends and supports MBHL’s commitment to continue collection of climate data at Doris North including snow surveys and installation of sensors for evaporation determination

• NRCan recommends that the new data be incorporated into yearly reviews, refinements of the estimates of climatic parameters, water balance adjustments and thermal modelling for infrastructure design

Baseline Climate Data

• NRCan agrees that construction techniques employed for facilities such as roads and buildings should result in preservation of permafrost

• NRCan recommends that MBHL utilize a freezing point of –2°C for all foundation design to ensure that potentially thaw unstable marine sediments remain frozen (below –2°C)

Impacts on terrain related to surface infrastructure

• NRCan agrees that there will be minimal impact over the 2 year operating period

• NRCan supports the proposal to monitor temperature in the underground mine to better understand the geothermal regime

Impacts of underground mining on permafrost thermal regime

• Fine-grained material required for dam construction• Site within Tail Lake footprint at water level elevation 29.5 m has been

proposed as borrow source area

Issues• Insufficient information is available to determine that adequate material

for construction of the fine-grained dam core can be extracted from this location

Recommendations• NRCan recommends and supports MHBL’s commitment to conduct

additional investigations to characterize the borrow deposit as part of the final detailed dam design

• If sufficient material is not available at this site MHBL must locate a suitable borrow deposit or propose alternatives to the dam design

Impacts related to extraction of borrow resources

Issues• Ice-rich marine sediments are widespread around the periphery of Tail

Lake

• Potential for thawing of permafrost as lake level rises

• Thawing of ice rich marine sediments may lead to erosion, solifluction and slumping and increase suspended sediment load of the lake

Recommendations• NRCan recommends that the proponent characterize the sensitivity of the

Tail Lake shoreline to permafrost degradation and erosion

• MHBL must also consider that erosion and slumping may occur on gentler slopes as well as the steeper slopes identified along the periphery of Tail Lake

Impacts of rising water levels on shoreline stability of Tail Lake

Issues

• Detailed thermal modelling is required to:– determine if the dam core will remain frozen and impermeable under

current and future climatic conditions

– determine settlement that may occur beneath the dam as thawing occurs in response to increasing water levels

• Improved characterization of thermal and physical properties of dam and foundation material is required to:– adequately model the thermal regime of the dam

– assess total and differential settlement and stability of dam

– assess seepage

Processed Ore Containment Area(Tail Lake tailings impoundment)

Recommendations

• Further characterization of both the thermal and hydraulic properties of the dam (in particular the core) and foundation materials are required

• Better assessment of lateral and vertical variation of ice content is required to improve the evaluation of differential settlement and dam stability

• Climate change has been considered but transient modelling must be conducted to determine timing of thawing of the core and the position of the active layer over time

• The above are required to ensure that that the top of the frozen core remains above the maximum water level

Processed Ore Containment Area(Tail Lake tailings impoundment)

5 - 7°C

C hange in M eanA nnua l A irTem pera ture(2x CO - p resent)2

3 - 52 - 31 - 20 - 1

0

0 km 500

Data from Environment Canada CCCma 1st generation coupled model

Issues• Proponent concludes final causeway surface will be at least 0.5 m above the highest

high-tide• Insufficient or inappropriate data used to select the 0.5 m value for wind-induced

surges and no consideration of waves which may ride on top of wind-induced surges• Final causeway surface would not always be at least 0.5 m above the highest high-

tide and slightly higher surges and waves could overtop the jetty

Recommendations• NRCan recommends and supports MHBL’s commitment to further studies

including evaluation of foundation conditions, storm surges, propagated wave heights, sea ice pressures and pressures caused by barges as requirement for final jetty design

• Bathymetric data is lacking in vicinity of proposed wharf and collection of appropriate data on water depth is required

Physical Marine and Coastal Processes

Sea Water Levels

Issues• Sediments in shallow water (<3.5 m) are frozen with excess ice

– located along proposed wharf/jetty approaches– expected to partially thaw in summer– development of jetty may locally promote colder winter temperatures

and frost heave– thaw and heave of sediments present challenges to jetty design

• Thermal conditions in seabed sediment will be affected by method chosen for implementing jetty and wharf

Recommendation• Changes in freezing, thawing, ice content and potential for

heaving will have to be examined prior to final design

Nearshore permafrost

Issues• Jetty will act as a barrier to longshore transport of sediments

– may lead to enhanced erosion on downdrift side

– insufficient information to evaluate potential for erosion

• Presence of sand body at seabed in 5 m of water suggests wave and/or current activity sufficient to prevent fine sediment deposition

Recommendations• A more comprehensive evaluation of currents at the head of Robert’s Bay

in the vicinity of the jetty and wharf prior to construction

• Analysis of intact cores from sand body may contain a record of extreme events

Shoreline impacts of jetty

Issues• Runoff data may not be accurate and reliability of Tail Lake

water level records is uncertain– limited data available from automated recorders– supplemented by spot gauged measurements– corrections of staff gauge readings need to be justified– corrections to Tail Lake outflow records based on discharge records

in other lake basins in the area

Recommendations• Continued monitoring of water levels and discharge recommended

for entire open water season over project duration• Wide variations in discharge should be tested in sensitivity

analysis of water balance

Hydrological Monitoring

• Greater degree of planning required to accurately account for other sources and sinks of water to Tail Lake

– unclear if amount of reclaimed water from Tail Lake decreases as water quality in Tail Lake deteriorates

– will Doris Lake be used for processing if Tail Lake water quality deteriorates?

• Seepage estimates from Tail Lake should be confirmed by installing seepage meters in Tail Lake

– estimate ground water flow from Tail Lake during seasonal thaw

– determine if seepage increases as head in Tail Lake increases

• Potential for water to be released from permafrost during mining– groundwater inflow not adequately characterized and may be underestimated

– better characterization of hydraulic parameters required to determine pumping requirements for mine water disposal

Additional water balance/water quality issues

• NRCan supports proposed plan to monitor permafrost and terrain stability– little detail provided– required at critical locations such as dam alignments and periphery of

Tail Lake

• Continuous monitoring of effluent rates to Tail Lake and weekly testing for deleterious substances in effluent and Tail and Doris Lakes required– recognition of irregularities– determine if mitigation measures must be implemented

• NRCan recommends that meteorological, hydrologic, and chemical testing and measurement continue for project duration– incorporate results into yearly review and water balance

Monitoring