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

UNECE WORSHOP ON TDS, YEREVAN, November 2007

TAILING DAMSRISK ANALYSIS AND MANAGMENT

Pavel DanihelkaEva Červeňanová


CONTENT:

• Examples of historical accidents

• Introduction to risk theory

• Risk analysis principles

• Basics of application of risk analysis to tailing dams safety

• Conclusion


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


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.


History of major tailing dams accidents

Source: „ICOLD Bulletin 121“


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:


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.


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.


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.


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


Distribution of causes of tailing dams accidents

Source: ICOLD Bulletin 121


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


Conclusion:

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


2. INTRODUCTION TO RISK THEORY

• Definition of – Hazard– Risk

• Risk and its quantification (measurement)

• Principles of risk reduction/management


DEFINITION OF TERMS

SOURCE OF DANGER

=

POTENTIAL TO CAUSE DAMAGE


RISK

=

PROBABILITY x GRAVITY OF ACCIDENT (EVENT)


RISK

DANGEROUSITY IDENTICAL

RISK

DIFFERENT

DIFFERENCE: MANAGEMENT OF RISK


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


• 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)


• 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


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


• Acceptability of risk

PROBABILITY

GRAVITY

NON ACCEPTABLE

CONDITIONALLY ACCEPTABLE

ACCEPTABLE

ACTION NECESSARY

ACTION VOLUNTARY

RISK MITIGATION


ACCEPTABILITY OF RISK

• Decision is socio-politic, not scientific

• Decision should include all stakeholders

• All types of risk should be evaluation together


How to decrease risk?


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


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


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


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.


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


SCENARIO DESCRIPTION

(DAM DESTRUCTION)

„TOP“ EVENT

1

2

3

4

5

6

7

CAUSES CONSEQUENCES

SCENARIO 1

SCENARIO 2

EACH SCENARIO NUMBERED


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


Frequency of „100 year“ flooding


One mythus:„We operate it long time without accident, so safety is

prooved“


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


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


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


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.)


RISK ASSESSMENTFollowing frequency and gravity, scenarios

are put to the risk matrix

1

7

6

5

4

3

2

PROBABILITY

GRAVITY


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


BARIERS OF PREVENTION / PROTECTION

Source system

Target system

Initial event

Other conditions

Flux of danger

INITIAL EVENT


BARRIER

BARRIER

BARRIER

CATASTROPHEBARRIER OF FLUX DOMINO EFFECT

INITIAL EVENT


PROTECTION OF TARGETREMOTION OF SOURCE


SAFETY MANAGEMENT

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

• Emergency preparedness


NEAR MISSES: „HUNTING FOR DEVIATIONS“

ELIMINATED

CATASTROPHE

BIG ACCIDENTS / LOSSES

SMALL ACCIDENTS/ LOSSES

DEVIATIONS


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


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


And something for thinking…


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 ?


THINK AGAIN!


THINK AGAIN!


• Thank you for your attention !

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

Documents

unece worshop

major risk slide

management of risk slide

stava accident slide

m3 of tailings

tailing dams risk analysis

management neglected

cause damage slide