Caps and Covers for AMD Control the Canadian Experience

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Caps and Covers for AMD Control the Canadian
Experience
Gilles Tremblay MEND/NOAMI/GARD Guide
Secretariats
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Presentation Highlights

• Background
• Environmental Stewardship
• MEND
• Dry Covers
• Water Covers
• Technology Transfer

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Environmental Responsibility

• Increasing emphasis on finding solutions to mine
  waste management issues
• Solutions to be both environmentally sound and
  cost-effective
• Need to meet increasingly stringent regulatory
  requirements and public concerns, and to reduce
  environmental liability

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Integrated Mine Site Rehabilitation Strategy

• Physical stabilization of site Removal of
  structural components
• Waste management and decommissioning Cover
  technologies
• Dry covers
• Water covers
• Water treatment technologies
• Chemical or active treatment
• Passive treatment

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Current Trends in Canada

• Enlightened sustainable development policies
• Mining recognized as a sustainable industry
• Environmental problems can be prevented
• No public
• New mining and waste technologies
• Site - specific solutions and criteria
• Legislation in Canada
• Metal Mine Effluent Regulations
• Schedule 2
• Provincial
• Cooperative problem solving
• Consortiums

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Mine Environment Neutral Drainage (MEND) Program

• The original MEND program (1989-1997) and its
  successors contributed enormously to
  understanding of acidic drainage and its
  prevention, and to increasing the transfer of
  knowledge to improve environmental management

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MEND Program

• 1989 2009
• Multistakeholder
• Volunteer participation
• 20 years 20 M
• Research and Technology Transfer
• http//mend.nrcan.gc.ca

Solbec
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Where metal leaching/acidic drainage is a
concern, mining is usually not a temporary use of
the land
Waite Amulet
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MEND Supported Technologies

• Prediction techniques
• Water covers for unoxidized and partially
  oxidized wastes
• Dry covers using soils/tailings, organic
  materials and geomembranes
• Mine waste management options for tailings,
  waste rock and treatment sludges
• Active and passive treatment
• Cold climate issues
  (permafrost)

Rabbit Lake, CAMECO
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Current Work Plan

• Addresses the top ranking research priorities
  identified by Canadian experts
• Closure Management/Case Studies
• Verification of technologies
• Metal Leaching - Neutral pH
• Passive Treatment
• Sludge Management
• Monitoring
• Early Prediction
• Cold Temperature Effects
• Paste Backfill

Johnny Mountain Site in May
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CASE STUDIES
Johnny Mountain
Sulphurets
Mandy Lake, HBMS
East Kemptville, BHP Billiton
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Closure Management

• Cover Technologies
• Soil / Vegetation Cover
• Engineered Dry Covers
• Water Covers
• Saturation (elevated water table)
• Isolation of reactive mine waste
• Separation and segregation
• Backfilling (in-pit) and co-disposal
• Permafrost

Water covers
Dry covers
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Soil / Vegetation Cover - Successes / Challenges

• Successful site remediation
• Surface stabilization, and wind and water related
  erosion control
• Greatly improved site aesthetics
• Acidic drainage continues unabated
• Ongoing effluent collection and treatment
  required on a long-term basis (perpetuity)
• Sludge collection, disposal and management
  required

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Engineered Dry Covers

• Objectives
• Control the ingress of oxygen
• High saturation layer
• Multilayer design
• Control water infiltration
• Low permeability layer
• Store and release of moisture

• Types of Covers
• Soil/Tailings
• Organics
• Wood waste, peat, municipal waste
• Oxygen consuming barrier
• Availability/economics site specific
• Longevity
• Geomembranes

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Engineered Dry Covers

• Simple soil to composite engineered covers to
  limit both oxygen diffusion and moisture
  infiltration
• Factors affecting economic and feasibility of a
  cover system
• Site climatic conditions
• Availability of cover materials
• Distance to burrow sources
• Cover and waste material properties and
  conditions
• Surface topography and hydrology
• Cost 50k to 100k / ha may be more remote
  sites

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Engineered Dry Covers
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Engineered Dry Covers
Equity Silver Mine, BC
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Engineered Dry Covers - Alkaline Tailings LTA,
Barrick Gold, Québec
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Albert Mine, QC
Deinking Sludges Growth substrate
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Mine Poirier, BHP Billiton
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Unique solution using existing liner technology
Poirier 1998 - 2001
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Conclusions Mine Poirier

• Reclamation and closure design has resulted in
  substantial loading reductions to local watershed
• As a low permeability cover, the HDPE geomembrane
  with protective soil layer was cheaper than
  compacted clay requiring a much thicker
  frost-protection layer.
• HDPE is better suited than compacted clay to
  maintain integrity when subjected to highly
  differential settlement
• Monitoring continues to confirm the performance
  of the cover design

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Normetal
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Normetal- After
Normetal - 2008
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Victoria Junction Coal Preparation Plant (CBDC)
October 2006
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Whistle Pit

• Canadian Shield numerous bedrock outcrops and
  lakes
• Open pit mining (nickel) between 1988-91
  1994-98
• 6.4 Mt of waste rock on surface avg. S of 3
• Several acidic seeps developed
• Semi-humid climate annual precip. of 900 mm
  (30 as snow) potential evaporation of 520 mm

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INITIAL PERFORMANCE
Chemical Processes
Physical Processes
Biological Processes
- Dissolution
- Erosion
- Bioturbation
- Osmotic Consolidation
- Wet/Dry Cycles
- Root Penetration
- Freeze/Thaw Cycles
- Mineralogical Consolidation
- Burrowing Animals
- Sorption
- Extreme Local Climate Events
- Human Intervention
- Brushfires
- Precipitation
- Bacterial Clogging
- Dispersion/Erosion
- Consolidation
- Settlement
- Acidic Hydrolysis
LONG-TERM PERFORMANCE
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Dry Covers - Summary

• Small footprint and low to medium overall risk of
  catastrophic failure (depending on dam heights
  and water table elevation)
• Cover selection, design and placement dependent
  on site specific conditions
• Inclusion of local landforms conditions in
  overall cover design
• Local availability of cover materials is
  prerequisite
• Most engineered dry cover sites are still at
  experimental stages and no integrated, long-term
  performance record is available
• Longevity of membranes and cover materials root
  penetration and burrow animals
• Effects of vegetation on cover performance

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Dry Cover Manuals

• Dry Covers Manual (Micro-scale)
• 5-volume set available in hard copy or CD-ROM
• Summary
• Theory and Background
• Site Characterization, and Numerical Analyses
  of
• Cover Performance
• Field Performance Monitoring, Sustainable
• Performance of Cover Systems
• Case Studies
• Macro-Scale Cover Design and Performance
• Monitoring Manual (MEND Report 2.21.5)
• A Study to Improve our Ability to Accurately
  Predict the Long-term Performance of Dry Covers
  (www.inap.com.au/completed_reserach_projects)

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Green Mines Green EnergyBiosolids to Bioenergy

• CANMET led consortium to examine use of waste
  organic materials to rehabilitate mine sites and
  establish energy crops (canola, corn, soy etc.)
  for the production of biofuels

Biosolids Mine Tailings Energy Crops Green
Fuel
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Water Covers
Stanleigh Tailings Management Area Elliot Lake,
Ontario
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An Interactive, Complex System Optimize/Monitor
O2
Precipitation
Wind
Wave Action
Circulating currents
Water Cover
Local Mixing
Discharge
Inflow
Oxidation
Diss.O2 (diff.)
Oxidation
Resuspension
Diss. Men, H and SO4
Infiltration
Tailings
Groundwater
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Water Covers

• Water covers - oxygen limiting
• Diffusion barrier to both oxygen in the water
  cover and contaminants in the submerged waste
• Development of Diffusion Barriers Layers (DBL) at
  the water-waste and water-air interfaces
• Stagnant and well mixed water cover conditions
• Interaction of oxygenated water cover and
  submerged waste at the water waste interface

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Performance of Water Covers - Field Sites
(Man-made)

• Four study sites Denison, Panel, Quirke and
  Stanleigh Tailings Management Areas (TMAs)
  located at Elliot Lake, Ontario, Canada
• Low ore grade (0.1 U) and uranium market
  conditions led to mine closure in early to mid
  1990s
• Highly acid-generating pyritic uranium tailings
  containing 5-10 pyrite NNP -100 to -150 kg
  CaCO3/tonne
• Acid-leach milling process, very small to nil
  available alkalinity
• Extensive field sites having in-situ shallow
  water covers of minimum 1 m depth site
  rehabilitation during 1992 to 1999
• All sites on care and maintenance

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BHP Billiton (Rio Algom) Quirke Tailings
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Denison Mines - Before
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Denison Mines - After
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Performance of Water Covers

• Comparison based on yearly equivalent limestone
  addition per unit area for water cover and
  vegetated sites

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Shallow Water Cover at Louvicourt

• 1994 2004
• 28 pyrite (average)
• 45 of tailings deposited in man-made tailings
  impoundment
• 4.7Mm3 capacity in pond
• Design for 1m cover

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Louvicourt - Results

• Shallow water covers are effective
• Oxygen penetration typically less than 1cm
• Overall effect of periphyton biofilm positive

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Heath Steele
Panel
Man-made Impoundments Water covers
Equity Silver
Samatosum
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Manitou, Quebec
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Km 23
Km 19
Goldex
Km 12
Km 7
Km 2
Km 4
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Island Copper
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Summary - Covers

• Water covers and wet barriers offer unique
  opportunities at many sites
• Low maintenance closure and walk away options are
  desirable over long-term perpetual treatment

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MEND Highlights

• Toolbox of methods to reduce environmental
  impacts of mining
• Prevention best strategy
• Reduction in liability between 400M and 1
  billion, an impressive return on an initial
  investment of 17.5M
• Recognition for Canadas leadership role in
  addressing AD for metal mines

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X-cutting - Guideline Documents

• MEND Manual (MEND 5.4.2)
• Volume 1 Summary
• Volume 2 Sampling and Analyses
• Volume 3 Prediction
• Volume 4 Prevention and Control
• Volume 5 Treatment
• Volume 6 Monitoring
• In Progress....
• Prediction Manual - Update of the Draft BC
  Prediction Manual to be published as national
  document (NRCan)

Also available on CD
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X-Cutting Technology Transfer

• The MEND Monitor
• Workshops (gt30)
• Annual BC/MEND ARD/ML Workshops
• 15th 2008 Tailings Management
• Biannual regional workshops
• MEND Technology Transfer Workshops to Community
  Groups
• MEND Website at mend.nrcan.gc.ca
• MEND Reports (210 on paper and CD)
• Global Alliance
• GARD Guide Secretariat at MEND

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8th International Conference on Acid Rock
DrainageSkellefteå, Sweden2009
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For Further Information, contact

• Gilles Tremblay
• Manager MEND/NOAMI Secretariat
• Natural Resources Canada
• 328 - 555 Booth Street
• Ottawa, Ontario, Canada
• K1A 0G1
• gtrembla_at_nrcan.gc.ca
• http//www.abandoned-mines.org
• http//mend.nrcan.gc.ca

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Thank you very much, lets start the discussion