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Major Fail: Lessons from the Dam Breach at 
Mount Polley Mine, British Columbia 
Dylan McFarlane
Check Back in January 
Dirk Van Zyl 
Norbert Morgenstern 
Steven Vick 
Sources 
• KP Reports (2009, 2010) 
• Websites (Min...
1. The Failure 
2. Lessons
Mt. Polley
Mt. Polley
A Medium-Sized Copper-Gold Porphyry Mine
Upstream 
Downstream 
Centerline
Side-hill 
Impoundment
Perimeter Embankment 
Main Embankment 
& Buttress 
Failure Zone 
South Embankment
Fraser River 
100 km 
5 km 
Polley Lake 
Quesnel Lake 
Hazeltine Creek 
Mount Polley Mine 
Tailings Facility 
Likely 
Sacr...
42t4hthAJuugluy s2t0 210414 
Polley Lake 
2 km 
Quesnel Lake 
Hazeltine Creek 
Mount 
Polley 
Mine 
Tailings Facility
Before 
Polley Lake 
2 km 
Quesnel Lake 
Hazeltine Creek 
Mount 
Polley 
Mine 
Tailings Facility
After 
Polley Lake 
2 km 
Quesnel Lake 
Hazeltine Creek 
Mount 
Polley 
Mine 
Tailings Facility
Fraser River 
100 km 
Polley Lake 
2 km 
Quesnel Lake 
Hazeltine Creek 
Mount 
Polley 
Mine 
Tailings Facility
Timeline of Events 
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
F...
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failures 
2009 – 2012...
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failures 
2009 – 2012...
85 Mt  500 Mt 
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failu...
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failures 
2009 – 2012...
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failures 
2009 – 2012...
1997 
Operation 
2001 – 2005 
Closure - 
Restart 
2005 – 2006 
Expansion & 
Dam Review 
2010 
Human 
Failures 
2009 – 2012...
Perimeter Embankment 
Main Embankment 
& Buttress 
Failure Zone 
South Embankment 
2010 Tension Crack
Independent Engineering Review Board 
Dirk Van Zyl 
Norbert Morgenstern 
Steven Vick
Materials Description Amount 
Water Supernatant water 10.6 Mm3 
Slurry Tailings solids 7.3 Mm3 
Interstitial water 6.5 Mm3...
Tahltan Elders Blockade Red Chris Mine
The Response 
Mount Polley Mining Company 
Indefinite care and maintenance 
Conceptual Interim Erosion and Sediment 
Contr...
Communication
Remediation Plan
Dyke Construction
Pumping out Polley Lake
22.5 Tonnes of Heli-seeding
Access
How Did it Happen?
Jack Caldwell’s Ideas 
Upstream failure 
Piping 
Embankment crack due to soil creep 
Embankment crack due to differential ...
Forces Driving Failure > Forces Resisting Failure
Dam Breach empirical evidence suggests 80 – 120m breach width
Events Leading to Failure 
Weak lacustrine FOUNDATION (artesian?)  creep, deformation; unstable 
Tailings rise too fast, ...
Weak, wet foundation soils? 
Artesian 
Foundation 
Main Embankment 4mm Displacement  Buttress Required 
2013: Buttressing...
Water Surplus – No Beaching 
2011 2012 2013 
May 2014 June 2014 July 2014
Incidents & Violations since 2012 (from MoE) 
2012 
Failure to report height exceedance for tailings pond 
August: Overflo...
Global Mining 
British Columbia 
Community 
MPMC 
• Tarnished brand image 
• Social license to operate 
• Attracting young...
How many salmon will die? 
Sediment Plume 
Tens of kilometres square near Hazeltine and 
Raft Creek 
Mostly deep (< 65m) 
...
Costs 1: Direct Remediation and Reclamation 
Respected geotechnical engineers: $50 – 500 M 
Imperial Metals estimate: 
Clo...
Costs 2: Indirect Reputational, Social, Political 
Minimum $ 500 M 
My Starting Guess: $ 1 – 20 Billion 
Some Costs: Acces...
A Picture Says a Thousand Words
Disastrous for Brand Image
Lessons, Thoughts, Ideas
Mine Wastes: Black Swans of Mining 
• An expensive, non-productive, complex asset 
• Significant societal risks  In PERPE...
TSFs – Watch the Corners, Manage Water 
Stress wants to flow,; alignment, foundation… 
Waters cause a lot of failures – ne...
Twenty Years of Progress
Failure Rates Improved but are they 
Acceptable? 
(Oboni & Oboni 2014) 
3.5 MAJOR dams breach 
on average per year 
(1974 ...
In the long term, the probability of 
failure of all tailings dams is one. 
Therefore in quantifying risks, all we 
need t...
Disclosure, Discounts & Dry Stacks 
Disclose Data & Reports Online  SOCIAL AUDIT 
Practice of Discounting Closure Costs B...
Conclusion 
Mount Polley was a human failure – Managers, Engineers, Regulators 
Entirely Preventable 
We, Salmon, are Luck...
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
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Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia

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22 Oct 2014 Research seminar at the Camborne School of Mines on the tailings dam failure at Mount Polley mine, British Columbia.

Published in: Engineering
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Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia

  1. 1. Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia Dylan McFarlane
  2. 2. Check Back in January Dirk Van Zyl Norbert Morgenstern Steven Vick Sources • KP Reports (2009, 2010) • Websites (Miner & Regulator) • Media • Blogs (ithinkmining.com)
  3. 3. 1. The Failure 2. Lessons
  4. 4. Mt. Polley
  5. 5. Mt. Polley
  6. 6. A Medium-Sized Copper-Gold Porphyry Mine
  7. 7. Upstream Downstream Centerline
  8. 8. Side-hill Impoundment
  9. 9. Perimeter Embankment Main Embankment & Buttress Failure Zone South Embankment
  10. 10. Fraser River 100 km 5 km Polley Lake Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility Likely Sacred Fire Quesnel River
  11. 11. 42t4hthAJuugluy s2t0 210414 Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
  12. 12. Before Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
  13. 13. After Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
  14. 14. Fraser River 100 km Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
  15. 15. Timeline of Events 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures Quesnel Lake 2009 – 2012 Water Surplus 2014 Disaster Closure
  16. 16. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure
  17. 17. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure
  18. 18. 85 Mt  500 Mt 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure
  19. 19. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure Review risk classification Dam breach and inundation analysis 10-15 m tension crack  stability assessment Lacustrine unit 4mm displacement, buttress Poor beach development (since 2008) 40% piezometers failed (since 2006) Lack of monitoring phreatic surface, flows Water surplus  stochastic analysis 85 Mt ultimate storage capacity exceeded
  20. 20. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2013/2014 Disaster Closure Review water surplus issue Structural engineer needed Sedimentation ponds Groundwater monitoring Emergency preparedness Liberal BC Premier Gordon Campbell Regulatory staff cut 20% Risk burden  consultants
  21. 21. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure Gerald MacBurney: Dam foreman, whistleblower 2013: AMEC said 5 Mt rock buttress needed  but less than 1 Mt received 2014: Media frenzy Eco-babble
  22. 22. Perimeter Embankment Main Embankment & Buttress Failure Zone South Embankment 2010 Tension Crack
  23. 23. Independent Engineering Review Board Dirk Van Zyl Norbert Morgenstern Steven Vick
  24. 24. Materials Description Amount Water Supernatant water 10.6 Mm3 Slurry Tailings solids 7.3 Mm3 Interstitial water 6.5 Mm3 Construction Soil, gravel, agg. 0.6 Mm3 Total 25.0 Mm3 Non-acid generating (ave. pH 8.5) Acute exceedances in total metal contents: • Cu, Fe…..Zn, Se, Cr, V Chronic exceedances: turbidity, suspended solids Physical impacts • Erosion and scour • Deposition of trees and woody debris • Deposition of tailings and eroded earth Plume 25 – 35m below surface extending for tens of square kilometres • Deep station (65 m) = highest concentration (>200 μg Cu vs. Aquatic Life WQG 7 μg) LUCKY!!! No ARD No dissolved, bioavailable metals No impacts beyond Quesnel
  25. 25. Tahltan Elders Blockade Red Chris Mine
  26. 26. The Response Mount Polley Mining Company Indefinite care and maintenance Conceptual Interim Erosion and Sediment Control Plan • Improve water quality • Reduce re-mobilization potential • Manage TSF flows to Springer Pit Ask for money! Mount Polley funding Red Chris Dev. Regulators Order, Emergency, Water Ban Independent Expert Engineering Review Dam Safety Inspections for all permitted mines in BC including: Review of Consequence risk classification Provide a lot of information!
  27. 27. Communication
  28. 28. Remediation Plan
  29. 29. Dyke Construction
  30. 30. Pumping out Polley Lake
  31. 31. 22.5 Tonnes of Heli-seeding
  32. 32. Access
  33. 33. How Did it Happen?
  34. 34. Jack Caldwell’s Ideas Upstream failure Piping Embankment crack due to soil creep Embankment crack due to differential foundation deformation Ithinkmining.com
  35. 35. Forces Driving Failure > Forces Resisting Failure
  36. 36. Dam Breach empirical evidence suggests 80 – 120m breach width
  37. 37. Events Leading to Failure Weak lacustrine FOUNDATION (artesian?)  creep, deformation; unstable Tailings rise too fast, poor beaching TOO MUCH WATER Poor adherence to OSM (Operation, Maintenance and Surveillance) manual Overtopping incidents weaken structure (+/- piping) Borrow pit excavation weakens foundation POOR MANAGEMENT Buttress: too little, too late Overtopping, slip failure, collapse
  38. 38. Weak, wet foundation soils? Artesian Foundation Main Embankment 4mm Displacement  Buttress Required 2013: Buttressing Perimeter Embankment
  39. 39. Water Surplus – No Beaching 2011 2012 2013 May 2014 June 2014 July 2014
  40. 40. Incidents & Violations since 2012 (from MoE) 2012 Failure to report height exceedance for tailings pond August: Overflow of 150 m3 water Groundwater monitoring well data not submitted (twice) 2013 May: Dam breach (unreported, unverified) 2014 April: Overflow (spring freshet – pump blockage) May: Pond height exceedance
  41. 41. Global Mining British Columbia Community MPMC • Tarnished brand image • Social license to operate • Attracting young talent • Reputation, Trust, Legacy • Mandatory regulations • Blockades, permitting • Economic stress • Cultural loss • Sediment Plume – Salmon • Job losses • Bankruptcy Impacts
  42. 42. How many salmon will die? Sediment Plume Tens of kilometres square near Hazeltine and Raft Creek Mostly deep (< 65m) Turbidity, suspended solids: milky, opaque 25 – 35m plume mobilized by sill…? 1 million salmon fry – sensitive at 2 μg Cu
  43. 43. Costs 1: Direct Remediation and Reclamation Respected geotechnical engineers: $50 – 500 M Imperial Metals estimate: Closure bond $ 14.5 M (of $38 M) Total assets (minus liabilities) ~ $ 443 M ( - 50% ) Financing $ 115 M financing Insurance proceeds ??? ~~~ $150 M ??? Minus Red Chris mine commissioning costs ~ $70 M ~ $60 - 300 M
  44. 44. Costs 2: Indirect Reputational, Social, Political Minimum $ 500 M My Starting Guess: $ 1 – 20 Billion Some Costs: Access, Permitting, Delays, Blockades, SLO, Management, External Relations
  45. 45. A Picture Says a Thousand Words
  46. 46. Disastrous for Brand Image
  47. 47. Lessons, Thoughts, Ideas
  48. 48. Mine Wastes: Black Swans of Mining • An expensive, non-productive, complex asset • Significant societal risks  In PERPETUITY Highly Improbable Extreme Impact Explainable in Retro • Nobody wants operational responsibility, “Duty of Care”
  49. 49. TSFs – Watch the Corners, Manage Water Stress wants to flow,; alignment, foundation… Waters cause a lot of failures – never an “Act of God”
  50. 50. Twenty Years of Progress
  51. 51. Failure Rates Improved but are they Acceptable? (Oboni & Oboni 2014) 3.5 MAJOR dams breach on average per year (1974 – 1984) 0.7 MAJOR dams breach on average per year (1994 – 2004)
  52. 52. In the long term, the probability of failure of all tailings dams is one. Therefore in quantifying risks, all we need to consider is consequence. Steve Vick at Tailings and Mine Waste 2014
  53. 53. Disclosure, Discounts & Dry Stacks Disclose Data & Reports Online  SOCIAL AUDIT Practice of Discounting Closure Costs Bad (10% 30 Year LoM = ~ $ 0) Closure Costs Routinely Underestimated Long-term Performance Uncertainty Dry Stacked Tailings Good: Filter, Stack  Soil High CAPEX but Communities Love It! La Coipa, Chile 18ktpd Long-term Value Comparable only if Discount Practice Changes
  54. 54. Conclusion Mount Polley was a human failure – Managers, Engineers, Regulators Entirely Preventable We, Salmon, are Lucky it wasn’t Worse A Picture Says a Thousand Words Indirect Impacts in $$$ Billions Towards Sustainable Mining – Not Quite Yet Managing Mine Wastes Requires Holistic, Long-Term Approach

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