Skip to main content

 

Mount Polley spill blamed on design of embankment

Independent investigation finds foundation of earthen dam failed because of unstable underlying layers

CBC News Posted: Jan 30, 2015 5:56 AM PT Last Updated: Jan 30, 2015 12:32 PM PT

         

An earthen dam containing the Mount Polley mine tailings pond gave way early on the morning of Aug. 4, discharging 25 million cubic metres of contaminated water and mining waste into creeks and rivers near the town of Likely, B.C.

          An earthen dam containing the Mount Polley mine tailings pond gave way early on the morning of Aug. 4, discharging 25 million cubic metres of contaminated water and mining waste into creeks and rivers near the town of Likely, B.C. (Ministry of the Environment)         

Close

Looking ahead to Mount Polley report 7:26

 


  

Looking ahead to Mount Polley report 7:26

51 shares
 
Facebook
 
 
Twitter
 
 
Reddit
 
 
Google
 
 
Share
 
 
Email
 

Related Stories

An independent investigation has determined the breach of the Mount Polley mine tailings dam in B.C. was caused by a failure to detect a weak layer in its foundation, likening the massive embankment to a "loaded gun."

The report, which was released on Friday morning in Victoria, said the design failed to take into account the complexity of the instability of underlying glacial and pre-glacial layers under the retaining wall.

But the authors, geotechnicians Norbert Morganstern and Steve Vick, did not blame provincial inspectors for not detecting the problem beforehand. 

The investigators said the dam was built on a weak layer of glacial deposits that was undetected at the time, making the dam like a 'loaded gun."

They said the construction of a steep slope in the embankment as the dam was raised was "like pulling the trigger," causing the failure last summer.

They also concluded that massive volume of water in the tailings dam did not cause the dam to fail, but it did result in more tailings being released when it did breach.

Just eight days before the dam failed, a plan was approved to raise the dam further, but on the condition that a buttressing wall was put in place and the slope decreased, they said.

The investigators also made several recommendations to improve the safety of tailings dams, including updating the way they are designed, monitored and regulated in B.C.

Minister reacts to report

B.C.'s Minister of Energy and Mines Bill Bennett said he was thankful the panel was able to narrow down the failure to a specific cause.

"I am relieved that we have a cause," said Bennett. "Now that it has been identified, we can move forward."

hi-bc-120517-bill-bennett-4col

B.C.'s Minister of Energy and Mines Bill Bennett says the government will take action to prevent future tailings dam failures.  (CBC)

Bennett said the government would take action based on the report, including the inspection of about 100 existing tailings dams for similar risks, the establishment of review boards for existing dams and a core review of existing regulations.

"There should be zero failures of this nature.â€Ķ Everything must be done to ensure this does not happen again."

"This was a spectacularly horrible failure and it is one of a kind," said Bennett.

Bennett said there are still two other reports due later this year that will examine the failure of the dam.

One report by the chief inspector of mines, which is due in June, would identify those responsible for any mistakes made, said Bennett.

The other report would be coming from the Ministry of Environment's Conservation Officer Service.

Dam failed in August

When the dam at the Mount Polley tailings pond breached last August, it released 25 million cubic metres of contaminated water and mining waste, contaminating lakes, creeks and rivers near the town of Likely in the B.C. Interior.

The spill also raised questions about the inspection process for mines in the province. NDP Leader John Horgan has previously claimed a report from four years ago that detected a crack in the dam was hidden away.

mtpolley-feature

Investigators say the dam was built on a weak layer of glacial deposits that had been undetected.

Replies sorted oldest to newest

Engineering firm in collapsed Omai tailings pond fingered in another failure

August 20, 2014 | By | Filed Under News 

Canada – The engineering firm that designed the Mount Polley tailings pond containment system that collapsed on August 4, also designed a tailings dam that failed catastrophically in South America on Aug. 19, 1995.

A team at the Omai site shortly after the pond failure.

A team at the Omai site shortly after the pond failure.

Knight Pisold designed the tailings containment facility for the Canadian-owned Omai gold mine in Guyana. Before the accident, it had handed off operational responsibility to the mining company, which then hired another engineering consultant, the Canadian firm Golder Associates.
The Omai tailings dam collapse spilled an estimated 2.9 million cubic metres of toxic waste into the Essequibo River, the country’s biggest and most important watershed. (Some estimates run higher.)
Guyana’s President Cheddi Jagan, whose government held a five per cent share of the mining venture — it was the poor country’s largest private sector employer — and had been championing its economic benefits, called it “the country’s worst environmental disaster.”
A subsequent inquiry found no criminal liability and a civil class action suit was later dismissed.
It’s worth noting, perhaps, that by comparison the Mount Polley tailings dam failure, which B.C.’s Mines Minister Bill Bennett has equated with a simple natural landslide, spilled 14.5 million cubic metres — about five times as much contaminated waste as at Omai — into the Fraser River system, B.C’s biggest and most economically important watershed.
The most hazardous component in the Guyana accident was cyanide. The accident at Mount Polley released sediments contaminated mostly with arsenic and heavy metals.
Environment Canada lists on-site tailings disposal totals for the Mount Polley mine as including 969,993 kilograms of arsenic, 625,322 kilograms of lead, 19,940 kilograms of cadmium and 5,197 kilograms of mercury.
Environment Canada says of these listed compounds:
“Arsenic has been consistently demonstrated in numerous studies to cause cancer in humans” and “there is believed to be some chance of adverse health effects at any level of exposure.”
“Cadmium compounds have been classified as ‘probably carcinogenic to humans’ â€Ķ there is believed to be some chance of adverse health effects at any level of exposure.”
“Lead is a highly toxic metallic elementâ€Ķeven small amounts of lead can be hazardous to human health.
“Mercury is toxic and has the ability to pass the blood-brain barrier and affect the central nervous system.” The most common form of mercury uptake is eating contaminated fish. It’s of particular concern for pregnant and lactating women and small children whose developing nervous systems are vulnerable.
So, however one might choose to characterize the Mount Polley spill — and even if water quality levels are safe for now with river levels at summer lows — seeking to quell public concern with a simplistic comparison to a landslide seems curiously insensitive.
In one eerie foreshadowing of the current situation near Quesnel Lake, Knight Pisold warned the mine operator in Guyana when it handed off responsibility that modifying the tailings containment structure to increase volume might exceed its designed capacity and safety margins.
The Guyanese newspaper Stabroek News reported from the inquiry into the Omai tailings dam collapse that “Knight Pisold has told foreign media that the dam failed at a height at which they were no longer responsible, having been replaced at the end of 1992 by Omai’s current dam consultants, Golder Associates.” After Knight Pisold had ended its relationship with the Omai mine, the dam was raised significantly, and subsequently failed.
At the Mount Polley mine, Knight Pisold says that in 2011 it warned both the B.C. mine’s owners, Imperial Metals, and the provincial government that its original engineering was designed to accommodate a significantly lower water volume than was reportedly present when the dam breached.
“Knight Pisold informed Imperial Metals that we would not continue as the engineer of record for the Mount Polley Mine on Feb. 10, 2011, and subsequently ceased to perform that role,” the company said in a statement posted to its website last week.
“During the time we acted as engineer of record, the tailings storage facility at Mount Polley operated safely and as it was designed.”
The engineering firm says the facility was subjected to an independent third party assessment in 2006 and was found safe and structurally sound.
However, the company says, the tailings containment was designed to accommodate “a significantly lower water volume than the tailings storage facility reportedly held at the time of the breach.”
“Significant engineering and design changes were made subsequent to our involvement.”
Knight Pisold says that it wrote the B.C. government in 2010, just before leaving the operation, to warn that “the embankments and the overall tailings impoundment are getting large and it is extremely important that they be monitored, constructed and operate properly to prevent problems in the future.”
The B.C. government says it inspected the dam 33 times after Knight Pisold raised its concerns, including a geotechnical survey in 2013 and eight inspections in 2014.
This would mean that any modifications to structure, volume or operation in the three years before the dam’s collapse occurred under the regulatory oversight of the provincial Mines Ministry.

FM

An independent investigation has determined the breach of the Mount Polley mine tailings dam in B.C. was caused by a failure to detect a weak layer in its foundation, likening the massive embankment to a "loaded gun.

 

The report, which was released on Friday morning in Victoria, said the design failed to take into account the complexity of the instability of underlying glacial and pre-glacial layers under the retaining wall.

 

But the authors, geotechnicians Norbert Morganstern and Steve Vick, did not blame provincial inspectors for not detecting the problem beforehand. 

 

The investigators said the dam was built on a weak layer of glacial deposits that was undetected at the time, making the dam like a 'loaded gun."

 

They said the construction of a steep slope in the embankment as the dam was raised was "like pulling the trigger," causing the failure last summer.

 

 

Mount Polley spill blamed on design of embankment, Independent investigation finds foundation of earthen dam failed because of unstable underlying layers, CBC News Posted: Jan 30, 2015 5:56 AM PT, Last Updated: Jan 30, 2015 12:32 PM PT

While an integral part of the pre-ongoing and post-construction activities, unfortunately these conditions can exist for dams.

 

The glacial deposit area surely is not miniscule, hence it is extremely difficult to understand why this area was not detected, at least, during the construction period.

FM
Originally Posted by Churchill:

Wasn't Ramouthar a member of the OMAI board ?......he should be able to shed some light on this ......

Ramotar was a member of the OMAI Board and the GuySuCo Board.

GuySuCo fared worse while Ramotar sat on its board. Remember that Ramotar was PPP leader at that time, and he failed to uplift GuySuCo's performance.

FM

Add Reply

×
×
×
×
×
Link copied to your clipboard.
×
×