TAILING%20DAMS%20RISK%20ANALYSIS%20AND%20MANAGMENT

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TAILING DAMSRISK ANALYSIS AND MANAGMENT

• Pavel Danihelka
• Eva Cervenanová

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CONTENT

• Examples of historical accidents
• Introduction to risk theory
• Risk analysis principles
• Basics of application of risk analysis to tailing
  dams safety
• Conclusion

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EXAMPLES OF HISTORICAL ACCIDENTS

• At least 221 serious tailing dams accidents
  reported by UNEP

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
http//www.mineralresourcesforum.org/docs/pdfs/B
ulletin121.PDF
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Major tailing dams review cont.
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
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History of major tailing dams accidents
Source ICOLD Bulletin 121
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BAIA MARE
Case study
January 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.
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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.
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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.
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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.
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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
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Distribution of causes of tailing dams accidents
Source ICOLD Bulletin 121
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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
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Conclusion

• Tailing dam is a risky installation able to cause
  major accident and so we have to treat it as
  major risk

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2. INTRODUCTION TO RISK THEORY

• Definition of
• Hazard
• Risk
• Risk and its quantification (measurement)
• Principles of risk reduction/management

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DEFINITION OF TERMS
SOURCE OF DANGER POTENTIAL TO CAUSE DAMAGE
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RISK PROBABILITY x GRAVITY OF ACCIDENT (EVENT)
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RISK
DANGEROUSITY IDENTICAL
RISK DIFFERENT
DIFFERENCE MANAGEMENT OF RISK
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FLUX OF DANGER
DOMINO EFFECT
CATASTROPHE
Example Stava accident
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• 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

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• 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

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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)
PROBABILITY
GRAVITY
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• Acceptability of risk

NON ACCEPTABLE
PROBABILITY
ACTION NECESSARY
ACCEPTABLE
RISK MITIGATION
ACTION VOLUNTARY
CONDITIONALLY ACCEPTABLE
GRAVITY
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ACCEPTABILITY OF RISK

• Decision is socio-politic, not scientific
• Decision should include all stakeholders
• All types of risk should be evaluation together

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How to decrease risk?
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RISK ANALYSIS PROCESS
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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

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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

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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.

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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

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SCENARIO DESCRIPTION
EACH SCENARIO NUMBERED
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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

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Frequency of 100 year flooding
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One mythusWe operate it long time without
accident, so safety is prooved
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• 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

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Costs of Failure

• Physical failure recent large failures 30 to
  100 million in direct costs
• Environmental failure some recent clean-up
  liabilities to several 100s 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

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• 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

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Severity of impact an example (source
Robertson GeoConsultants Inc.)
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RISK ASSESSMENT

• Following frequency and gravity, scenarios are
  put to the risk matrix

PROBABILITY
GRAVITY
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GOALS SETTING Non-axeptable (red zone)
scenarios immediate action Conditionally
acceptable (yellow zone) scenatios action
envisaged
PROBABILITY
1
5
2
7
GRAVITY
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BARIERS OF PREVENTION / PROTECTION
BARRIER
BARRIER
BARRIER
REMOTION OF SOURCE
PROTECTION OF TARGET
BARRIER OF FLUX DOMINO EFFECT
CATASTROPHE
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SAFETY MANAGEMENT

• Prevention part (even three part of bow-tie
  diagram)
• Emergency preparedness

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NEAR MISSES HUNTING FOR DEVIATIONS
ELIMINATED
CATASTROPHE
BIG ACCIDENTS / LOSSES
SMALL ACCIDENTS/ LOSSES
DEVIATIONS
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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

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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

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And something for thinking
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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 ?

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THINK AGAIN!
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THINK AGAIN!
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• Thank you for your attention !