Tailings Facilities - An Introduction from an Insurance Perspective

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Tailings Facilities - An Introduction from an
InsurancePerspective

• Tailings Dam Failures
• Lessons Learned and Recent Examples

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BASIC TAILINGS DAM CONSTRUCTION METHODS

• Upstream
• Centreline
• Downstream
• Water Retention

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TAILINGS DAM CONSTRUCTION METHODS
A1
UPSTREAM
A2, A22A1
CENTRELINE
A3, A33A1
DOWNSTREAM
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SOURCES OF INFORMATION

• USCOLD 1994 Summary
• UNEP 1996 Summary
• Press Releases
• KC Review Experience

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TAILINGS INCIDENT TYPE SUMMARY USCOLD (1994)
PERCENT OF INCIDENT TYPE FOR EACH ACTIVITY STATUS
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NUMBER OF INCIDENTS BY ORE TYPE
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NUMBER OF INCIDENTS BY DAM HEIGHT
Casapalca, Peru (Structural) Casapalca, Peru
(Seismic)
Cyprus Thompson Creek, USA Unidentified, Eastern
USA
La Belle, USA TN Consolidated Coal No.1, USA
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FAILURES AND ACCIDENTS BY CAUSE
NUMBER OF INCIDENTS, EACH TYPE
PERCENT (TOTAL FAILURES AND ACCIDENTS ONLY)
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INCIDENTS BY DAM TYPE
NUMBER OF INCIDENTS, EACH TYPE
PERCENT (TOTAL INCIDENTS ONLY)
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DAM FAILURES

• Los Frailes, Spain, 1998
• Amatista, Peru, 1996
• Marcopper, Philippines, 1996
• Omai, Guyana, 1995
• Sullivan, BC, Canada, 1991

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LOS FRAILES, SPAIN, 1998

• Failure on April 25, 1998
• 20 m high downstream tailings dam failed
• Foundation shear failure through marl clay
  foundation soils
• Release of 3 to 5 million m3 of pond water and
  tailings into Rio Agrio and Rio Guadiamar
• 2000 to 5000 ha of cropland contaminated by
  heavy metals
• Mine shutdown for several months
• Global press coverage

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Los Frailes Tailings Breach - 1998
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Merrispruit Tailings Breach - 1994
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AMATISTA, PERU, 1996

• Failure on November 12, 1996 due to M6.4
  earthquake, 135 km SE
• 45 m high side hill upstream tailings dam failed
• Seismic liquefaction of upstream tailings dam
• 2 Inactive tailings dams did not fail
• Flow runout of about 600 m
• Inundated small river, contamination downstream
  affecting croplands
• Remediation limited to excavating channel for
  river

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AMATISTA TAILINGS DAM
Toe of Runout
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MARCOPPER, PHILIPPINES, 1996

• Failure on March 24, 1996 on Marinduque Island,
  Philippines
• Tailings released from worked-out Tapian open
  pit
• Concrete plug failed in 2.2 km Makulapnit
  drainage tunnel inundating 27 km stretch of the
  rivers
• 4 million tonnes of tailings flowed into
  Makulapnit and Boac rivers
• Mine shutdown permanently
• Criminal charges pending

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OMAI, GUYANA, 1995

• Failure on August 19, 1995
• Tailings pond released through 45 m high
  downstream tailings dam
• Filter failure likely concentrated around
  through-dam diversion conduit
• 1.3 million m3 of pond water released into
  Omai/Essequibo rivers
• Minimal environmental damage despite contrary T
  press coverage
• Mine shutdown for 6 months
• On-going class action suit in Canada

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Omai Tailings Dam No. 1 Configuration
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Omai Tailings Dam No. 1
Forensic trench mapping with stress and
displacement patterns
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SULLIVAN MINE BRITISH COLUMBIA, 1991

• Failure on August 23, 1991 near Kimberley, BC
• Downstream slope failure of upstream tailings
  dam
• Static liquefaction during dyke raising
• No tailings released
• Failure involved 300 m section of 12 m high
  dyke, 75,000 m3 of material

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RECENT COST EXPERIENCE
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LESSONS LEARNED

• Retain experienced tailings engineering
  consultants
• Retain review board with authority to change
  design
• Perform third party audits of tailings
  operations regularly
• Document everything
• Install, read and react to instrumentation
• Maintain simple, dynamic emergency response plan