Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
•
4 recomendaciones•2,369 vistas
The Mount Polley mine tailings dam failure in 2014 released about 25 million cubic meters of mining waste and wastewater into nearby waterways. An investigation found the failure was likely due to inadequate design and construction of the dam given the foundation conditions. Key lessons from the failure include the need for more stringent dam design, construction and monitoring practices, as well as improved water management, to prevent such catastrophic failures from occurring. The failure had wide-ranging environmental, social, economic and reputational impacts, costing at least $50 million but potentially billions due to lost salmon habitat and the mining company's damaged brand.
Recomendados
Recomendados
Más contenido relacionado
La actualidad más candente
La actualidad más candente (20)
Similar a Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
Similar a Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia (20)
Último
Último (20)
Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia
- 1. Major Fail: Lessons from the Dam Breach at Mount Polley Mine, British Columbia Dylan McFarlane
- 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. 1. The Failure 2. Lessons
- 4. Mt. Polley
- 5. Mt. Polley
- 6. A Medium-Sized Copper-Gold Porphyry Mine
- 10. Perimeter Embankment Main Embankment & Buttress Failure Zone South Embankment
- 11. Fraser River 100 km 5 km Polley Lake Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility Likely Sacred Fire Quesnel River
- 12. 42t4hthAJuugluy s2t0 210414 Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
- 13. Before Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
- 14. After Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
- 15. Fraser River 100 km Polley Lake 2 km Quesnel Lake Hazeltine Creek Mount Polley Mine Tailings Facility
- 17. 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
- 18. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure
- 19. 1997 Operation 2001 – 2005 Closure - Restart 2005 – 2006 Expansion & Dam Review 2010 Human Failures 2009 – 2012 Water Surplus 2014 Disaster Closure
- 20. 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
- 21. 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
- 22. 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
- 23. 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
- 24. Perimeter Embankment Main Embankment & Buttress Failure Zone South Embankment 2010 Tension Crack
- 25. Independent Engineering Review Board Dirk Van Zyl Norbert Morgenstern Steven Vick
- 26. 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
- 27. Tahltan Elders Blockade Red Chris Mine
- 28. 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!
- 29. Communication
- 31. Remediation Plan
- 36. Pumping out Polley Lake
- 37. 22.5 Tonnes of Heli-seeding
- 41. Access
- 43. How Did it Happen?
- 44. Jack Caldwell’s Ideas Upstream failure Piping Embankment crack due to soil creep Embankment crack due to differential foundation deformation Ithinkmining.com
- 46. Forces Driving Failure > Forces Resisting Failure
- 47. Dam Breach empirical evidence suggests 80 – 120m breach width
- 53. 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
- 54. Weak, wet foundation soils? Artesian Foundation Main Embankment 4mm Displacement Buttress Required 2013: Buttressing Perimeter Embankment
- 55. Water Surplus – No Beaching 2011 2012 2013 May 2014 June 2014 July 2014
- 56. 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
- 57. 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
- 58. 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
- 59. 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
- 60. 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
- 61. A Picture Says a Thousand Words
- 62. Disastrous for Brand Image
- 65. 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”
- 67. TSFs – Watch the Corners, Manage Water Stress wants to flow,; alignment, foundation… Waters cause a lot of failures – never an “Act of God”
- 68. Twenty Years of Progress
- 69. 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)
- 70. 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
- 71. 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
- 72. 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
Notas del editor
- Not really research, but some thoughts and musings on this extraordinary, upsetting, unfortunate failure event.
- The Failure How did it happen? Geotechnical Why did it happen? Human failures leading up to the event Impacts Costs Lessons Failure Rates Engineering Responsibility Managing Mine Wastes ? Risk Uncertainty Future Costs & Solutions For most of you uninterested in F-N curves and risk tolerability this will all be pretty boring so hopefully I’ve included enough pretty pictures for you. Feel free to interrupt at any time.
- Quesnel Lake ~160m deep (up to 600m) largest lake BC. Fjord/glacial lake, with a sill 20km west of lake outlet
- Importance of water flows and managing the water balance
- Dam length ~ 4 kilometers
- Scale and north area and labels!
- BC climate – wet. Deep glacial fjord lakes and watercourses support fishing, tourism, and logging industries.
- BC climate – wet. Deep glacial fjord lakes and watercourses support fishing, tourism, and logging industries.
- BC climate – wet. Deep glacial fjord lakes and watercourses support fishing, tourism, and logging industries.
- Drains measured only once since June 2009, instead of weekly as Operation, Maintenance and Surveillance Manual recommends. Piezometer monthly, or weekly during construction.
- Williams Lake “opposed to any
- Gerald MacBurney “Eco-babble” – This Twittered fish caught in a lake ~400km South, off the Fraser River. “skinned peeled off like never before, sick”.
- Dam length ~ 4 kilometers
- 52% drop in value
- Latest empirical evidence suggests 40m dam breach result in 80 – 120 m wide section, but it is much wider, and different morphology.
- Could easily look at latent and active failures. All human error in engineering or management judgement
- Environmental – not so bad Social – pretty bad Political – very bad, fallout for Liberal party in BC Financial – very bad for Imperial, pretty bad for North America, bad for global mining projects Geotechnical Engineering – bad for AMEC Regulatory – very bad failed oversight No significant, adverse, long term impacts, but uncertainty about sediment plume (monitoring)
- All the stuff nobody wants. Negative connotation. (Waste rock, tailings, low grade and spent ore – leach operation). Geologists say it’s not ore, Metallurgists send it out the mill, Engineers don’t want to see it, and in doesn’t make money for Managers. May also includes industrial wastes (fly ash from coal plants) top soil or overburden (non-reactive), etc. Mine Wastes are not inspiring. When 3rd years do a feasibility study, wastes understandably receive limited attention. Planning and operation typically employs the “observational approach”. Let’s see what happens. NOBODY WANTS RESPONSIBILITY FOR IT. Usually the aspect of development plans that communities protest The importance of mine wastes. Contain all the stuff that we don’t want. The largest risk at mine sites. Facilities much larger than pits and mine infrastructure. Very costly to manage responsibly (managers often cut resources during market downturns). Risk that lasts in “perpetuity” (activist phrase) ie FOREVER. Acid and metal leaching potential. Very complex to design, build, operate, and close. And in long term (as all geos and geotechs here can appreciate), these structures will all fail into soup and flow into our rivers. Managing the risks of mine wastes is paramount to any notion of “responsible” or “sustainable” mining.