NRCans Expertise

1
NRCans 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)

2
Caros 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 ?

3
Explosives Manufacture Storage
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Explosives Manufacture Storage (contd)
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Explosives Manufacture Storage (contd)
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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

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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
8
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

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Acid Rock Drainage Potential

• 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

10
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

11
Baseline Climate Data

• MBHL has acknowledged shortcomings of climate
  data
• Recommendations
• NRCan recommends and supports MBHLs 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

12
Impacts on terrain related to surface
infrastructure

• 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 2C for all foundation design to ensure
  that potentially thaw unstable marine sediments
  remain frozen (below 2C)

Impacts of underground mining on permafrost
thermal regime

• 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

13
Impacts related to extraction of borrow resources

• 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 MHBLs 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

14
Impacts of rising water levels on shoreline
stability of Tail Lake

• 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

15
Processed Ore Containment Area(Tail Lake
tailings impoundment)

• 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

16
Processed Ore Containment Area(Tail Lake
tailings impoundment)
Data from Environment Canada CCCma 1st generation
coupled model

• 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

17
Physical Marine and Coastal ProcessesSea Water
Levels

• 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 MHBLs 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

18
Nearshore permafrost

• Issues
• Sediments in shallow water (lt3.5 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

19
Shoreline impacts of jetty

• 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 Roberts 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

20
Hydrological Monitoring

• 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

21
Additional water balance/water quality issues

• 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

22
Monitoring

• 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