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TAILING DAMS RISK ANALYSIS AND MANAGMENT

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  1. TAILING DAMSRISK ANALYSIS AND MANAGMENT Pavel Danihelka Eva Červeňanová UNECE WORSHOP ON TDS, YEREVAN, November 2007

  2. CONTENT: • Examples of historical accidents • Introduction to risk theory • Risk analysis principles • Basics of application of risk analysis to tailing dams safety • Conclusion UNECE WORSHOP ON TDS, YEREVAN, November 2007

  3. EXAMPLES OF HISTORICAL ACCIDENTS At least 221 serious tailing dams accidents reported by UNEP*: * http://www.mineralresourcesforum.org/docs/pdfs/Bulletin121.PDF UNECE WORSHOP ON TDS, YEREVAN, November 2007

  4. Major tailing dams review – cont. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  5. History of major tailing dams accidents Source: „ICOLD Bulletin 121“ UNECE WORSHOP ON TDS, YEREVAN, November 2007

  6. Case study: BAIA MARE January 30, 2000in Baia Mare (Romania) the biggest freshwater disaster in Central and Eastern Europe. Nearly 100,000 m3 of cyanide and heavy metal-contamined liquid spilled into the Lupus stream, reaching the Szamos, Tisza, and finally Danube rivers and killing hundreds of tones of fish and poisoning the drinking water of more than 2 million people in Hungary. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  7. LOS FRAILES April 25, 1998 tailings dam failure of the Los Frailes lead-zinc mine at Aznalcóllar near Seville, Spain, released 4-5 million cubic meters of toxic tailings slurries and liquid into nearby Río Agrio, a tributary to Río Guadiamar. The slurry wave covered several thousand hectares of farmland, and it threatens the Doñana National Park, a UN World Heritage Area. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  8. STAVA On July 19, 1985, a fluorite tailings dam of Prealpi Mineraia failed at Stava, Trento, Italy. 200,000 m3 of tailings flowed 4.2 km downstream at a speed of up to 90 km/h, killing 268 people and destroying 62 buildings. The total surface area affected was 43.5 hectares. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  9. AITIK On September 8, 2000, the tailings dam of Boliden's Aitik copper mine near Gällivare in northern Sweden failed over a length of 120 meters. This resulted in the spill of 2.5 million cubic meters of liquid into an adjacent settling pond. Boliden subsequently released 1.5 million cubic meters of water from the settling pond into the environment to secure the stability of the settling pond. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  10. VARIABILITY OF CAUSES OF ACCIDENT • Inadequate management • Lack of control of hydrological system • Error in site selection and investigation • Unsatisfactory foundation, lack of stability of downstream slope • Seepage • Overtoping • Earthquake MAIN ROOT CAUSE: RISK ANALYSIS AND MANAGEMENT NEGLECTED UNECE WORSHOP ON TDS, YEREVAN, November 2007

  11. Distribution of causes of tailing dams accidents Source: ICOLD Bulletin 121 UNECE WORSHOP ON TDS, YEREVAN, November 2007

  12. VARIABILITY OF CONSEQUENCES • Flooding, wave of slurry • Contamination of surface water, living organisms (biota), intoxication • Drinking and irrigation water contamination (surface) • Drinking and irrigation water (underground) contamination • Soil contamination • As consequence of 2),3),4)ad.5 : Food chain contamination »FREQUENTLY TRANSBOUNDARY EFFECT UNECE WORSHOP ON TDS, YEREVAN, November 2007

  13. Conclusion: • Tailing dam is a risky installation able to cause major accident and so we have to treat it as major risk UNECE WORSHOP ON TDS, YEREVAN, November 2007

  14. 2. INTRODUCTION TO RISK THEORY • Definition of • Hazard • Risk • Risk and its quantification (measurement) • Principles of risk reduction/management UNECE WORSHOP ON TDS, YEREVAN, November 2007

  15. DEFINITION OF TERMS SOURCE OF DANGER = POTENTIAL TO CAUSE DAMAGE UNECE WORSHOP ON TDS, YEREVAN, November 2007

  16. RISK = PROBABILITY x GRAVITY OF ACCIDENT (EVENT) UNECE WORSHOP ON TDS, YEREVAN, November 2007

  17. RISK DIFFERENCE: MANAGEMENT OF RISK UNECE WORSHOP ON TDS, YEREVAN, November 2007

  18. Initial event Other conditions Source system Flux of danger Target system SYSTEM 3 SYSTEM 2 SYSTEM 1 INITIAL EVENT FLUX OF DANGER DOMINO EFFECT: CATASTROPHE Example: Stava accident UNECE WORSHOP ON TDS, YEREVAN, November 2007

  19. Targets system: • Population around tailings dam • Environment • Surface water • Underground water • Soil • Living organisms • Material and financial losses (direct) • Functioning of enterprise (including indirect losses) • Flux of danger: • Movement of material • Flux of energy • Flux of information UNECE WORSHOP ON TDS, YEREVAN, November 2007

  20. Sources of danger: • Having potential (energy) to cause damage • Having potential to weaken structure, resistance, resilience of our system (tailing dam and its environment) • Direct to dam stability • Indirect including human error • To consequences UNECE WORSHOP ON TDS, YEREVAN, November 2007

  21. B C A D QUANTIFICATION OF RISK • RISK MATRIX PROBABILITY A – banal case B – frequent accident with low consequences (minor injury, small contamination, ...) C – disaster with high probability (walking in minefield) D – disaster with low probability (nuclear power plant, major incident) GRAVITY UNECE WORSHOP ON TDS, YEREVAN, November 2007

  22. NON ACCEPTABLE • Acceptability of risk PROBABILITY ACTION NECESSARY ACCEPTABLE RISK MITIGATION ACTION VOLUNTARY CONDITIONALLY ACCEPTABLE GRAVITY UNECE WORSHOP ON TDS, YEREVAN, November 2007

  23. ACCEPTABILITY OF RISK • Decision is socio-politic, not scientific • Decision should include all stakeholders • All types of risk should be evaluation together UNECE WORSHOP ON TDS, YEREVAN, November 2007

  24. How to decrease risk? UNECE WORSHOP ON TDS, YEREVAN, November 2007

  25. Selection of sources of danger Feedback and control Scenarios proposal Risk assessment Goals setting Barriers ofprevention ETA FTA AMDEC FMEA HAZOP WHAT-IF Etc. Risk management IMPACT Residual risk PROBALITY TECHNICAL BARRIERS ORGANISATION BARIERS RISK ANALYSIS PROCESS UNECE WORSHOP ON TDS, YEREVAN, November 2007

  26. SOURCES OF DANGER • Direct to dam stability: • Active environment (rain, snow, freeze…) • Earthquake • Geological conditions • Domino effect • Indirect to dam (including human error): • Wrong conception • Construction failure • Material failure • Bad maintenance • Lack of control • To consequence: • Water and sludge movement • Mechanical contamination by solid particles • Chemical toxicity / ecotoxicity • Radioactivity UNECE WORSHOP ON TDS, YEREVAN, November 2007

  27. SCENARIO PROPOSAL • All plausible scenario should be involved in preliminary conspiration • All stages of life-time must be considered • Those having minor impact omitted • Similar combined to groups • Described as combination of events in time • Finally, we are able to compare limited number of scenarios only UNECE WORSHOP ON TDS, YEREVAN, November 2007

  28. TOOLS HELPING TO DEFINE SCENARIO • Examples of past accidents • Near-misses and accidents on site • Control list • WHAT-IF • ETA • FTA • AMDEC • FMEA • HAZOP • Etc. UNECE WORSHOP ON TDS, YEREVAN, November 2007

  29. Past accidents analysis • In site – during all life of it • In similar places you operate, including near-misses. Mind the necessity of reporting. • In mine industry generally • TAILINGS DAMS, RISK OF DANGEROUS OCCURRENCES, Lessons learnt from practical experiences, ICOLD- UNEP 2001, Bulletin 121, ISSN 0534-8293 • APELL for Mining: Guidance for the Mining Industry in RaisingAwareness and Preparedness for Emergenciesat Local Level, Technical report No. 41, UN Publications 2001, ISBN 92-807-2035 UNECE WORSHOP ON TDS, YEREVAN, November 2007

  30. CAUSES CONSEQUENCES 1 2 „TOP“ EVENT 3 4 (DAM DESTRUCTION) 5 6 7 SCENARIO 1 SCENARIO 2 SCENARIO DESCRIPTION EACH SCENARIO NUMBERED UNECE WORSHOP ON TDS, YEREVAN, November 2007

  31. RISK ASSESMENT: • FREQUENCY x CONSEQUENCES (IMPACT) • FREQUENCY: • From past accidents (high degree of uncertainty) • From initial events frequency and FTA by boolean algebra • Avoid omitting of low frequency events (not to limit only to 100-year water or earthquake) • Human factor extremely important UNECE WORSHOP ON TDS, YEREVAN, November 2007

  32. Frequency of „100 year“ flooding UNECE WORSHOP ON TDS, YEREVAN, November 2007

  33. One mythus:„We operate it long time without accident, so safety is prooved“ UNECE WORSHOP ON TDS, YEREVAN, November 2007

  34. CONSEQUENCES: • Consequences to human lives, health and well being.Evaluation of consequences with stakeholders necessary • Direct costs (remediation, compensation, ...) • Social disturbance • Consequence to environment – short time and long time impacts • Economical consequences and operability • Indirect costs UNECE WORSHOP ON TDS, YEREVAN, November 2007

  35. Costs of Failure Physical failure: recent large failures $30 to $100 million in direct costs Environmental failure: some recent clean-up liabilities to several $100’s of millions Closure liability: some recent examples in $500 milon to $4 billion range Industry/investor impacts: Shareholder value losses and industry imposed constraints and costs amounting to many billions of dollars UNECE WORSHOP ON TDS, YEREVAN, November 2007

  36. CONSEQUENCES II: • The scales of consequences should be defined before analysis is done(4-6 grades) • All possible targets should have the same scales of consequences(e.g. Grade X is comparable in all target systems) • The most serious consequence is selected • Internal values of society/enterprise become to be clarified UNECE WORSHOP ON TDS, YEREVAN, November 2007

  37. Severity of impact – an example (source: Robertson GeoConsultants Inc.) UNECE WORSHOP ON TDS, YEREVAN, November 2007

  38. 1 5 2 4 3 7 6 RISK ASSESSMENT Following frequency and gravity, scenarios are put to the risk matrix PROBABILITY GRAVITY UNECE WORSHOP ON TDS, YEREVAN, November 2007

  39. GOALS SETTING: Non-axeptable (red zone) scenarios: immediate action Conditionally acceptable (yellow zone) scenatios: action envisaged 1 5 2 4 3 7 6 PROBABILITY 1 5 2 7 GRAVITY UNECE WORSHOP ON TDS, YEREVAN, November 2007

  40. Initial event Other conditions Source system Flux of danger Target system SYSTEM 3 SYSTEM 3 SYSTEM 2 SYSTEM 2 SYSTEM 1 SYSTEM 1 INITIAL EVENT INITIAL EVENT BARIERS OF PREVENTION / PROTECTION BARRIER BARRIER REMOTION OF SOURCE BARRIER PROTECTION OF TARGET BARRIER OF FLUX DOMINO EFFECT CATASTROPHE UNECE WORSHOP ON TDS, YEREVAN, November 2007

  41. SAFETY MANAGEMENT • Prevention part (even three part of bow-tie diagram) • Emergency preparedness UNECE WORSHOP ON TDS, YEREVAN, November 2007

  42. NEAR MISSES: „HUNTING FOR DEVIATIONS“ ELIMINATED CATASTROPHE BIG ACCIDENTS / LOSSES SMALL ACCIDENTS/ LOSSES DEVIATIONS UNECE WORSHOP ON TDS, YEREVAN, November 2007

  43. Emergency preparedness • Preparedness to accident, even with low probability • Training and not only desktop one • Information of all potentially involved • Crisis management including training • Open and honest communication with municipalities, emergency response teams, government bodies (inspection…) • Communication with media UNECE WORSHOP ON TDS, YEREVAN, November 2007

  44. RECOMMENDATIONS 1) Detailed site investigation by experienced geologists and geotechnical engineers to determine possible potential for failure, with in situ and laboratory testing to determine the properties of the foundation materials. 2) Application of state of the art procedures for design. 3) Expert construction supervision and inspection. 4) Laboratory testing for “as built” conditions. 5) Routine monitoring. 6) Safety evaluation for observed conditions including “as built” geometry, materials and shearing resistance. Observations and effects of piezometric conditions. 7) Dam break studies. 8) Contingency plans. 9) Periodic safety audits UNECE WORSHOP ON TDS, YEREVAN, November 2007

  45. And something for thinking… UNECE WORSHOP ON TDS, YEREVAN, November 2007

  46. DO WE REALLY NEED ACCIDENT PREVENTION? • You've carefully thought out all the angles. • You've done it a thousand times. • It comes naturally to you. • You know what you're doing, its what you've been trained to do your whole life. • Nothing could possibly go wrong, right ? UNECE WORSHOP ON TDS, YEREVAN, November 2007

  47. THINK AGAIN! UNECE WORSHOP ON TDS, YEREVAN, November 2007

  48. THINK AGAIN! UNECE WORSHOP ON TDS, YEREVAN, November 2007

  49. Thank you for your attention ! UNECE WORSHOP ON TDS, YEREVAN, November 2007