Download NRCan`s Expertise Geohazards (earthquakes, landslides etc.)

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)
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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
Miramar Hope Bay Ltd.
Doris North Project:
NIRB Hearing
NRCan/Geological Survey of
Canada Presentations
Presented by Sharon Smith
Geological Survey of Canada
July 11 - 13, 2004
22 May 2017
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
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
Baseline Climate Data
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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
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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
Baseline Climate Data
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
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 –2°C
for all foundation design to ensure that potentially thaw unstable
marine sediments remain frozen (below –2°C)
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
Impacts related to extraction of
borrow resources
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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
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Insufficient information is available to determine that adequate material
for construction of the fine-grained dam core can be extracted from this
location
Recommendations
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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 of rising water levels on
shoreline stability of Tail Lake
Issues
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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
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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
Processed Ore Containment Area
(Tail Lake tailings impoundment)
Issues
• Detailed thermal modelling is required to:
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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
Change in Mean
Annual Air
Temperature
(2xCO2 - present)
Processed Ore Containment Area
(Tail Lake tailings impoundment)
Recommendations
5 - 7°C
3-5
2-3
1-2
0-1
0
0 km 500
Data from Environment Canada
CCCma 1st generation coupled model
• 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
Physical Marine and Coastal Processes
Sea Water Levels
Issues
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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 hightide and slightly higher surges and waves could overtop the jetty
Recommendations
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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
Nearshore permafrost
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
Shoreline impacts of jetty
Issues
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Jetty will act as a barrier to longshore transport of sediments
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may lead to enhanced erosion on downdrift side
– insufficient information to evaluate potential for erosion
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Presence of sand body at seabed in 5 m of water suggests wave and/or
current activity sufficient to prevent fine sediment deposition
Recommendations
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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
Hydrological Monitoring
Issues
• Runoff data may not be accurate and reliability of Tail Lake water
level records is uncertain
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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
Additional water balance/water
quality issues
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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?
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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
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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
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