Mount Polley – Canadian Tailings Dam Failure

Read WaterLegacy’s commentary piece in the Star Tribune, Counterpoint: ‘Modern Mining’ Isn’t the Plan Here. Advocacy Director, Paula Maccabee, explains:

“PolyMet is a bargain basement project that would fail to protect northern Minnesota’s priceless water resources and that would put public health at risk.”

“More than six years ago, before PolyMet’s first draft environmental-impact statement was released to the public, PolyMet and the “responsible” agencies rejected tailings-waste improvements, even as they admitted that placing tailings in a lined facility or reducing water in tailings would mitigate environmental harms. These better technologies to reduce water-quality impacts were screened out in 2009, because the operational costs “would be high.” Neither of these safer alternatives has been analyzed since.”

News on the bottom line one year after the Mount Polley tailings dam collapse:

Recent reports show that, as a result of the Mount Polley disaster, mining in British Columbia could cost taxpayers more than a mine produces in its entire lifetime!

“Mount Polley Mine will never produce enough profitable ore to pay back the public for the damage done to the environment. Two engineering firms estimated the damage at around $600 million dollars.”                                               


READ R. Manning, One Year Later from Common Ground

One year after the Mount Polley disaster, impacted Hazeltine Creek now resembles a dry canyon. Photo by Kim Goforth.


Mount Polley tailings dam was designed by the same engineers designing the PolyMet tailings disposal facility.

Figure from the Report on Mount Polley Tailings Storage Facility Breach


What happened at Mount Polley?

On Monday, August 4, 2014, a sunny summer day, the tailings dam at the Mount Polley copper-nickel mine collapsed. The breach released an estimated 24.4 million cubic meters of tailings and wastewater – or 6.3 billion gallons (there are 264 gallons in a cubic meter) – into Polley Lake in central British Columbia. The Mount Polley mine tailings spill was nearly 70 percent bigger than first estimated.

Loss of containment was sudden, with no warning.

The spill caused Polley Lake to rise by 1.5 meters (4.9 ft) – Hazeltine Creek, which flows out of Lake Polley, was transformed from a 2-metre-wide (6.6 ft) stream to a 50-metre-across (160 ft) “wasteland” and Cariboo Creek was also affected. By August 8, the spill had reached Quesnel Lake, considered until then one of the cleanest deep-water lakes in the world.

Learn more about what happened when the Mount Polley tailings dam collapsed.

Mount Polley ‘s tailings dam was designed by Knight Piesold, the same engineers designing the PolyMet tailings disposal facility.

And like PolyMet, Imperial Metals, the mining company responsible for Mount Polley, claimed it was using modern technology.

TAKE ACTION NOW: Send a letter to Governor Dayton and the Minnesota Department of Natural Resources requesting that PolyMet be required to analyze dry tailings disposal alternatives and that no permits be granted to PolyMet allowing wet tailings disposal on the existing LTVSMC tailings site.

Why did the Mount Polley Tailings Impoundment fail?

The British Columbia government, along with tribal governments, hired an independent panel of investigators who concluded that the very design of the project with water-saturated tailings was the cause of the failure. As the Independent Expert Engineering Investigation and Review Panel concluded in its January 30, 2015, Report on Mount Polley Tailings Storage Facility Breach:

“[T]he dominant contribution to the failure resides in the design.”

What did the Independent Review Panel for Mount Polley recommend to prevent future disasters at tailings impoundments?

The Independent Review Panel recommended dry stack tailings disposal as Best Available Technology to prevent catastrophic failure of sulfide mine tailings dams:

“[T]he future requires not only an improved adoption of best applicable practices (BAP), but also a migration to best available technology (BAT). Examples of BAT are filtered, unsaturated, compacted tailings and reduction in the use of water covers in a closure setting.”

The Panel explained, “There are no overriding technical impediments to more widespread adoption of filtered tailings technology.”

The Panel also challenged the practice of maintaining a water cover over tailings to reduce reactivity, stating that so-called water cover runs counter to best available technology principles.

The Panel acknowledged that capital costs for dry stack tailings are more than they are for unfiltered piles of wet tailings, but criticized as a “limited view” cost comparisons that do not include risk costs, both direct and indirect, associated with failure potential. The panel advised, “Full consideration of life cycle costs including closure, environmental liabilities, and other externalities will provide a more complete economic picture.”

Read the complete Independent Expert Engineering Investigation and Review Panel, Report on Mount Polley Tailings Storage Facility Breach here.

What are the implications of the Mount Polley disaster for the PolyMet sulfide mine project?

First, the PolyMet project proposes wet, unfiltered tailings disposal approximately 200 feet high on top of an existing four square miles of tailings piles, created by LTV Steel Mining Company. The LTVSMC tailings piles are heaped on top of three streams, compressed peat, and up to 42 feet of glacial sediments.

This map shows the wetlands and streams beneath the existing LTVSMC tailings disposal site.

The PolyMet tailings would be saturated and covered with water. This schematic drawing of the PolyMet tailings disposal site from the PolyMet Supplemental Draft Environmental Impact Statement shows how PolyMet tailings would be heaped on top of LTVSMC tailings and covered with water.

In other words, the PolyMet design strongly resembles the tailings disposal methods used at the Mount Polley copper-nickel mine. And as First Nations Summit Grand Chief Ed John noted earlier this year as he reflected on the Mt. Polley catastrophe, “The best available technology (not the best practices standard) is required for existing and future mines instead of water/tailings storage and the use of lakes.”

WaterLegacy Seeks Best Available Technology Alternative to Protect Minnesota Waters – Dry Tailings Disposal for PolyMet

In comments on the PolyMet Supplemental Draft Environmental Impact Statement in March 2014, the Grand Portage Band of Lake Superior Chippewa (Read the complete comments) and WaterLegacy (Read the complete comments) requested that alternatives for PolyMet tailings waste, including dry tailings disposal, be studied in order to reduce impacts on water quality from polluted seepage.

WaterLegacy has updated our request to the State and Federal agencies responsible for analyzing and approving permits for the PolyMet sulfide mine project and tailings waste facility:

“WaterLegacy explicitly requests that, in the Final EIS, the Co-Lead Agencies analyze alternatives for dry stack tailings, both on and off the site currently proposed for PolyMet tailings disposal…

“WaterLegacy further requests that the analysis of dry stack tailings alternatives for the PolyMet project include a rigorous cost-benefit analysis focused on long-term costs during operations, reclamation and closure. The long-term benefits of dry stack tailings disposal for PolyMet could include reductions in adverse effects to water quality and wetlands as a result of tailings basin seepage, reduced costs for long-term water quality treatment, reduction in adverse impacts to water quality and wetlands in the event of a catastrophic impoundment failure, and avoided financial and ecological costs of remediation.”

Read the complete March 18, 2015 letter from WaterLegacy to Co-Lead Agencies. WaterLegacy’s letter requests the use of the best available technology — that is, the use of dry stack tailings — based on the Mount Polley Report.