UNECE WORSHOP ON TDS, YEREVAN, November 2007
TAILING DAMSRISK ANALYSIS AND MANAGMENT
Pavel DanihelkaEva Červeňanová
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
EXAMPLES OF HISTORICAL ACCIDENTS
At least 221 serious tailing dams accidents reported by UNEP*:
* http://www.mineralresourcesforum.org/docs/pdfs/Bulletin121.PDF
Mine name/ Location
Incident Date
Impact
Baia Mare, Romania
30.01.2000 100,000 m3 cyanide contaminated water with some tailings released
Baia Borsa, Romania
10.03.2000 22,000 t of tailings contaminated by heavy metals released
Merriespruit, South Africa
22.02.1994 17 deaths, 500,000 m3 slurry flowed 2 km
UNECE WORSHOP ON TDS, YEREVAN, November 2007
Mine name/ Location
Incident Date
Impact
Buffalo Creek, USA
26.02.1972 125 deaths, 500 homes destroyed
Mufilira, Zambia
25.09.1970 89 deaths, 68,000 m3 into mine workings
Omai, Guyana 19.08.1995 4.2 million m3 cyanide slurry released
Placer, Philippines
02.09.1995 12 deaths, 50,000 m3 released
Los Frailes, Spain
24.04.1998 released 4-5 million cubic meters of toxic tailings slurries
Stava, Italy 19.07.1985 269 deaths, tailings flowed up to 8 km
Aitik mine, Sweden
09.08.2000 1.8 million m3 water released
Major tailing dams review – cont.
UNECE WORSHOP ON TDS, YEREVAN, November 2007
History of major tailing dams accidents
Source: „ICOLD Bulletin 121“
UNECE WORSHOP ON TDS, YEREVAN, November 2007
BAIA MAREJanuary 30, 2000 in 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.
Case study:
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
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
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
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
Distribution of causes of tailing dams accidents
Source: ICOLD Bulletin 121
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
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
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
DEFINITION OF TERMS
SOURCE OF DANGER
=
POTENTIAL TO CAUSE DAMAGE
UNECE WORSHOP ON TDS, YEREVAN, November 2007
RISK
=
PROBABILITY x GRAVITY OF ACCIDENT (EVENT)
UNECE WORSHOP ON TDS, YEREVAN, November 2007
RISK
DANGEROUSITY IDENTICAL
RISK
DIFFERENT
DIFFERENCE: MANAGEMENT OF RISK
UNECE WORSHOP ON TDS, YEREVAN, November 2007
INITIAL EVENT
SYSTEM 1SYSTEM 2 SYSTEM 3
FLUX OF DANGER
Source system
Target system
Initial event
Other conditions
Flux of danger
DOMINO EFFECT:
CATASTROPHEExample: Stava accident
UNECE WORSHOP ON TDS, YEREVAN, November 2007
• Flux of danger:Movement of
materialFlux of energyFlux of
information
• 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)
UNECE WORSHOP ON TDS, YEREVAN, November 2007
• 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
QUANTIFICATION OF RISK
• RISK MATRIX
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)
B C
A D
PROBABILITY
GRAVITY
UNECE WORSHOP ON TDS, YEREVAN, November 2007
• Acceptability of risk
PROBABILITY
GRAVITY
NON ACCEPTABLE
CONDITIONALLY ACCEPTABLE
ACCEPTABLE
ACTION NECESSARY
ACTION VOLUNTARY
RISK MITIGATION
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
How to decrease risk?
UNECE WORSHOP ON TDS, YEREVAN, November 2007
RISK ANALYSIS PROCESS
Scenarios proposal
ETAFTAAMDECFMEAHAZOPWHAT-IFEtc.
Selection of sources of
danger
Risk assessment
Goals setting
Barriers of prevention
Feedback and control
Risk management
Residual riskIMPACT
PROBALITY
TECHNICAL BARRIERS
ORGANISATION BARIERS
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
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
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
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 Raising Awareness and Preparedness for Emergencies at Local Level, Technical report No. 41, UN Publications 2001, ISBN 92-807-2035
UNECE WORSHOP ON TDS, YEREVAN, November 2007
SCENARIO DESCRIPTION
(DAM DESTRUCTION)
„TOP“ EVENT
1
2
3
4
5
6
7
CAUSES CONSEQUENCES
SCENARIO 1
SCENARIO 2
EACH SCENARIO NUMBERED
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
Frequency of „100 year“ flooding
UNECE WORSHOP ON TDS, YEREVAN, November 2007
One mythus:„We operate it long time without accident, so safety is
prooved“
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
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
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
Public Concern and Image Health and Safety
Local, international and NGO outcry and demonstrations, results in large stock devaluation: severe restrictions of 'licence to practice';
Fatality or multiple fatalities expected
Local, international or NGO activism resulting in political and financial impacts on company 'license to do business' and in major proceedure or practice changes,
Severe injury or disability likely: or some potential for fatality
Occasional local, international and NGO attention requiring minor proceedure changes and additional public relations and communications
Lost time or injury likely: or some potential for serious injuries; or small risk of fatality.
Infrequent local, international and NGO attention addressed by normal public relations and communications
First aid required; or small risk of serious injury.
No international/ NGO attention No concern
Consequences Severity (Direct Costs)
Biological Impacts and Land Use
Regulatory Impacts and Concerns
Extreme (>$10 M) Catastrophic impact on habitat (irreversable and large)
Unable to meet regulatory obligations or expectations; shut down or severe restriction of operations
High ($1 - $10 M) Significant, irreversible impact on habitat or large, reversable
Regularly (more than once per year) or severely fail regulatory obligations or expectations - large increasing fines and loss of regulatory trust
Moderate ($0.1 - $1 M) Significant, reversible impact on habitat
Occasionally (less than one per year) or moderately fail regulatory obligations or expectations - fined or censured
Low ($0.01 - 0.1 M) Minor impact on habitat
Seldom or marginally exceed regulatory obligations or expectations. Some loss of regulatory tolerance, increasing reporting.
Negligible (<$0.01 M) No measurable impact
Do not exceed regulatory obligations or expectations
Severity of impact – an example (source: Robertson GeoConsultants Inc.)
UNECE WORSHOP ON TDS, YEREVAN, November 2007
RISK ASSESSMENTFollowing frequency and gravity, scenarios
are put to the risk matrix
1
7
6
5
4
3
2
PROBABILITY
GRAVITY
UNECE WORSHOP ON TDS, YEREVAN, November 2007
GOALS SETTING: Non-axeptable (red zone) scenarios: immediate action
Conditionally acceptable (yellow zone) scenatios: action envisaged
1
7
6
5
4
3
2
PROBABILITY
GRAVITY
5
2
1
7
UNECE WORSHOP ON TDS, YEREVAN, November 2007
BARIERS OF PREVENTION / PROTECTION
Source system
Target system
Initial event
Other conditions
Flux of danger
INITIAL EVENT
SYSTEM 1SYSTEM 2 SYSTEM 3
BARRIER
BARRIER
BARRIER
CATASTROPHEBARRIER OF FLUX DOMINO EFFECT
INITIAL EVENT
SYSTEM 1SYSTEM 2 SYSTEM 3
PROTECTION OF TARGETREMOTION OF SOURCE
UNECE WORSHOP ON TDS, YEREVAN, November 2007
SAFETY MANAGEMENT
• Prevention part (even three part of bow-tie diagram)
• Emergency preparedness
UNECE WORSHOP ON TDS, YEREVAN, November 2007
NEAR MISSES: „HUNTING FOR DEVIATIONS“
ELIMINATED
CATASTROPHE
BIG ACCIDENTS / LOSSES
SMALL ACCIDENTS/ LOSSES
DEVIATIONS
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
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
And something for thinking…
UNECE WORSHOP ON TDS, YEREVAN, November 2007
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
THINK AGAIN!
UNECE WORSHOP ON TDS, YEREVAN, November 2007
THINK AGAIN!
UNECE WORSHOP ON TDS, YEREVAN, November 2007
• Thank you for your attention !