Mining, Tailings and Dam Safety: the Mt. Polley Disaster and Next Steps Dr. Andrea Kennedy, Ph.D. Bridgeway Consulting for Adams Lake Indian Band 11 August 2014
Presentation Outline General Introduction Background: Tailings Dams and Causes of Tailings Dam failure Mt. Polley failure Mt. Polley disaster what next? Four key factors that influence mine tailings dam safety Ideas for Secwepemc to prevent this ever happening in Secwepemc territory
Disclaimer Dr. Andrea Kennedy and Bridgeway Consulting Inc. has had no direct involvement with the Mt. Polley mine, Mt. Polley tailings dam nor the Mt. Polley disaster. All information presented in this presentation is available from public sources. Any opinions provided by Dr. Kennedy are hers alone and based on her previous experience, not based on knowledge of the Mt. Polley mine and disaster directly. The information provided is presented as background only and not as advice. No decisions of any kind should be made based on this presentation. Dr. Andrea Kennedy is a professional engineer (nonpracticing ) with a Masters of Applied Science degree in civil engineering, water resources. Her research focussed on mine tailings impoundments and water management.
Background Tailings Tailings are extremely fine waste rock produced through the milling process at mines. High water content makes tailings difficult to manage, store and control. Tailings ponds or Tailings Storage Facilities TSFs are: embankment type dams, often built with a starter core of clay and till to prevent seepage. TSF sometimes used to store other waste or submerge PAG The relative volume of tailings from mines is increasing as ore quality and availability is decreasing.
Background Tailings and Dams Nearly 2,000 total dams in BC, most are earth-fill Possibly 200 are tailings dams Approximately one failure per year, mostly small dams and low consequence (for the years 1980-2010, MoE memorandum). ICOLD reports 36,000 large dams world wide with a failure rate of 1%. ICOLD reports tailings dams have double the failure rate of other large dams.
Typical Mechanisms of Failure The #1 cause of tailings dam failures has been unusual weather followed closely by management, in the period 2000-2009. 1. Overtopping as a precursor of dam failure, or primary cause. Overtopping can be due to inadequate spillway design, debris blockage of spillways, or settlement of the dam crest 2. Foundation defects, including settlement and slope instability 3. Piping which is internal erosion caused by seepage, is the third main cause. Seepage often occurs around hydraulic structures, such as pipes and spillways; through animal burrows; around roots of woody vegetation; and through cracks in dams, dam appurtenances, and dam foundations. 4. Structural failure of the materials used in dam construction 5. Inadequate maintenance. Source: ICOLD
Background: Mt. Polley Imperial Metals is a mid-sized BC-based mining company with extensive mine operating experience. Mt. Polley mine is a copper, gold mine and has held permits since 1992. There are still many unknowns Unknowns include: what led to the breach of the dam how severe the environmental damage will be when Imperial Metals will be able to stop the flow of fluid and tailings from the tailings storage pond consistency of the sediment/tailings content of the tailings who is responsible how the damage will be cleaned up and/or remediated
Mt. Polley Disaster What We Know Mt. Polley tailings dam breached August 4, 2014 10 million cubic metres of wastewater and 4.5 million cubic metres of contaminated tailings were released.
Mt. Polley Disaster What We Know Mt. Polley tailings dam breached August 4, 2014 10 million cubic metres of wastewater and 4.5 million cubic metres of contaminated tailings were released. 300 Imperial Metals employees are working on site, particularly on the temporary dyke to contain the tailings. Drinking water quality guidelines are currently met in most of Quesnel River. Ministry says Fraser River and Fraser River fish not affected.
Mt. Polley Disaster What We Know Much of the information about mine tailings ponds and dams is only available through FOI. BC MoE Reputable engineering firm, Knight Piesold completed their stint as engineer of record with the following warning sent to government and Imperial Metals: The embankments and the overall tailings impoundment are getting large and it is extremely important that they be monitored, constructed and operated properly to prevent problems in the future, Knight Piesold, managing director Ken Brouwer Technically, experts say that pore water pressures, freeboard and exposed beach are important factors in stability. According to public sources, Imperial Metals had begun research into water treatment with UBC for the discharge of water.
Mt. Polley What We Know The Ministry of Energy and Mines conducted a geotechnical inspection at the mine in September 2013, which resulted in no inspection orders related to the tailings facility. May 24, 2014: The ministry issued an advisory to Mount Polley Mining Corporation for exceedance of the height of effluent within the tailings impoundment. The effluent level returned to authorized levels commencing June 30, 2014. Brief extreme weather experienced in the Kamloops region at end of July, 2014. Link to Mt. Polley disaster unknown. Last measurements in early August 2014 indicated water levels were acceptable. At the time of the May incident, the distance between the water elevation and the crest of the dam (freeboard) was less than 1 meter. The water returned to authorized levels and freeboard was approximately 2.4 meters when last measured on Aug. 3. Mine records show that the operation was carrying out visual dam inspections and measuring freeboard at an acceptable frequency.
What next? For the Mt. Polley case, the path forward is unknown. Based on other dam failures: Multi-year clean up, largely funded by government. (Note that an August 9 th government bulletin said all clean-up would be funded by Imperial Metals.) Excavation of slurry / sediment Finger pointing in all directions Court cases and appeals Los Frailes tailings dam failed in Spain in 1998. Still in court in 2013. (15 years). Mining company Boliden. Boliden experienced another failure at Atitkek Sweden in 2000.
Four Key Factors 1. Regulations and Enforcement (what must be done) 2. Company Policies and Procedures (what corners are cut or what extra can be done) 3. Quality of Professional Services (Quality of advice, design, and maintenance work) 4. Natural effects (rain, floods, climate, embankment material variation, earthquakes, etc.)
Factor 1: Regulations Multiple Ministries with responsibilities for mine tailings ponds Dam safety regulations that apply to tailings dams are somewhat unclear, but typically the CDA Dam Safety Guidelines 2007 (and 2013 update). 2010 - MoE Dam Safety Program suggests there are risks related to the regulation and management of tailings dams outside the MoE. 2010 MoE suggested an internal review of all consequence classifications of dams. 2013/2014 Renewed MOU between Ministries renewing the MEMPR responsibility for tailings dams.
Factors 2 and 3: Company Policies and Procedures and Quality of Professional Services Unknown for Imperial Metals Evidence from other disciplines: Working with First Nations, consultation and consent.
Factor 4 Natural elements Reinstate meaningful regional hydrologic monitoring. Create some predictive capability that considers uncertainty of climate change for many elements. Review flood estimation practices.
Thoughts on Steps for Secwepemc Within a detailed Secwepemc mining policy, require: First Nation consent on the Hazard Classification of all dams. Best practices or clear minimum standards for design, maintenance, etc. Advocate for clear, specific mine tailings dam and TSF guidelines including for closure, specific to tailings. Provide Input Into Existing Regulations Inspection frequency Penalties