Archive for the ‘Tailings’ Category


Last night we played dominos.  Somebody remarked that the failure of the Mt Polley tailings facility was like a line of dominos standing on end and all lined up: push the first one over and it topples the next one that knocks over the next, until they all fall down and flow to Hazeltine Creek.

The first domino at Mt Polley was the clay that was too weak to resist the loads on it. The second domino at Mt Polley was the steep slope of the embankment—it had been designed to be inclined at two horizontal to one vertical—but because of a shortage of materials, had been built much steeper, namely at 1.3 horizontal to one vertical.

The third domino was the presence of water upstream of the embankment: the official report notes that if the elevation of the water had been but one meter lower, there would have been time & opportunity to fix the failing embankment.

The forth domino was the fluid tailings that were able to flow out and flow far once the embankment failed. The official report notes that if the pool of supernatant water had been kept far away from the perimeter , the tailings might have dried & consolidated and not been susceptible to flow in the absence of embankment containment.

In short, the dominos were perfectly lined up to fail en masse and catastrophically. And they did.  For the line had a factor of safety of 1.3 and a probability of failure of one.


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Still ploughing through the main report and many appendices.  The report focuses on the role of the foundation clays in initiating failure and even Bill Bennett has said this was the cause.  In the few minutes before I duck out to meet friends for a drink, let me comment on another issue that seems to be to be equally a important.

I refer to the amazing fact that the factor of safety was 1.3.  To quote the report on this:

The larger issue of what minimum factor of safety should be required was addressed in a September 19, 2012 communication from MEM to MPMC that deserves to be quoted at length:
The factor of safety for the main embankment is only marginally above the short-term design criteria of 1.3… AMEC has interpreted Table 6-2 from the 2007 Dam Safety Guidelines somewhat differently than I have seen in the past. This table recommends a minimum factor of safety of 1.3 at the end of construction and ‘before reservoir filling’ and a factor of safety of 1.5 at the ‘normal reservoir level.’ AMEC has interpreted the construction period as the entire pre-closure period, and this is open to debate. However, I consider that sufficient mitigation measures are in place (i.e., piezometer trigger thresholds) to support this more liberal interpretation in this instance.
Although questioning AMEC’s interpretation of the Dam Safety Guidelines, MEM was prepared to accept FS = 1.3, but only in conjunction with the Observational Method.

MEM accepted, with hesitation, the factor of safety of 1.3 when they knew it should have been 1.5 or higher.  The report says the Observational Method was misapplied.  The report says more on this issue:

Commenting on the implications of this value, MEM’s remarks on July 29, 2013, echoed its previous concerns:
The stability analyses indicate that the FOS for the ‘Main Embankment’ only marginally achieves the short term CDA design criteria of 1.3. … Previous correspondence from MEM has highlighted the difference in interpretation of the CDA Guidelines. AMEC has considered the construction period to be the entire ‘pre-closure’ period while CDA Guidelines, Table 6-2 recommends a minimum FOS of 1.3 ‘before reservoir filling,’ and a FOS of 1.5 at the ‘normal reservoir level.’
MEM requires a commitment from Mount Polley that they are moving toward increasing these FOS for the main embankment as part of subsequent dam raises in an effort to move toward achieving a long term FOS equal to 1.5. It is expected that Mount Polley will continue their transition to centerline construction and provide additional buttressing with time.
This marked a major change in direction. A factor of safety of 1.5, not 1.3, would become the governing criterion. Moreover, buttressing could no longer be deferred for either embankment.

But buttressing was deferred.  The factor of safety was not increased.  The dam failed.

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Mt Polley Report Availability

Here is the link to the site where you get the entire report just issued on the Mt Polley failure. https://www.mountpolleyreviewpanel.ca/

I have not read it yet, so refrain from comment.  Other than to remark that on the basis of the video by Morgenstern and Vick that it seems the factor of safety was too low and the embankment outer slope too steep.

As is said in the report:

The Panel concluded that the dominant contribution to the failure resides in the design. The design did not take into account the complexity of the sub-glacial and pre-glacial geological environment associated with the Perimeter Embankment foundation. As a result, foundation investigations and associated site characterization failed to identify a continuous [glaciolacustrine layer] GLU layer in the vicinity of the breach and to recognize that it was susceptible to undrained failure when subject to the stresses associated with the embankment.

The specifics of the failure were triggered by the construction of the downstream rockfill zone at a steep slope of 1.3 horizontal to 1.0 vertical. Had the downstream slope in recent years been flattened to 2.0 horizontal to 1.0 vertical, as proposed in the original design, failure would have been avoided. The slope was on the way to being flattened to meet its ultimate design criteria at the time of the incident.

The Panel reviewed the roles and responsibilities of the B.C.Ministry of Energy and Mines (the Regulator) and its interactions related to the MPMC TSF. The Panel found that inspections of the TSF would not have prevented failure and that the regulatory staff are well qualified to perform their responsibilities.The Panel found that the performance of the Regulator was as expected.

The Panel has examined the historical risk profile of the current portfolio of tailings dams in B.C.and concluded that the 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. Examples of BAP bear on improvements in corporate design responsibilities, and adoption of Independent Tailings Review Boards. Specific recommendations are made in the body of the report.



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He marched into my office and declared: “I am too old to consult at altitudes of 14,000 ft.”

I replied: “Many wonder if you do not have a severe case of BDSM sublimated in peer review at high altitudes.”

Today on the phone I spoke to someone later described to me as very influential in mining.  We agreed on nothing.  His job precludes him from rocking the boat.  His job demands assuaging potential clients.  He is nevertheless honorable in that he seeks to make mining good to the benefit of society.

We sought to establish what should be done to prevent a future Mt Polley.  Here are some ideas we did not agree on:

Professional Certification:  Screw P.Eng.  Make it necessary to be a T.Eng. (Professional Tailings Engineer). In short do what is done in California:  P.E. is OK.  But if you want to practice as a geotechnical engineer get registered as a professional geotechnical engineer–my daughter is thus registered and it makes a difference, I attest.  If you want to be a structural engineer, register as a professional structural engineer.  I have good friends who are registered as such and they are good.  And you have to pass examinations to become a Californian professional geotechnical engineer or a professional structural engineer. Afterall, you do not need to be a geotechnical engineer to be a tailings engineer—in fact it may be an impediment to try to be a tailings engineer based on ability as a geotechnical engineer.  As Sean Wells reminded us a long time ago, a tailings engineer needs to deal with fluids as well as solids.  A good geologist, environmental engineer, hydrogeologist and so on may become a better tailings engineer than a geotechnical engineer.

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On-Site T.Eng.  I visited fourteen tailings facilities last year.  There was a perfect correlation between the condition and safety of the tailings facility and the competence of the on-site tailings engineer.  Where no engineer, of any type, was on site, the tailings facility was a disaster waiting to happen.  Where there was an engineer on site or at least in the company, the tailings facility was well designed, well operated, and safe—at least in my opinion.

Peer Review.  I have never come across a safe tailings facility that did not have an independent peer review team.  Most tailings facilities I know where there is no peer review team are in danger of imminent failure, in spite of certification by the Canadian Mining Association–witness Mt Polley as a prime example.  The only problem with demanding a peer review team is that the folk who are peer reviewers are old and they snooze through meetings.  They jealously guard their assignments and exclude others.  They should be seeking instead to groom the fifty-year olds to be peer reviewers.  For the current crop of old peer reviewers will die and leave a vast vacuum behind. Common decency and moral professionalism, in my opinion, dictates that they should be grooming the next generation of tailings facility peer reviewers, those who are now fifty or so. And the old snoozers should fast move to lower altitudes.

Public Reports.  After the failure of the South African slimes dams at Bafokeng and Merriespruit, the government made it mandatory that every four months an independent consultant prepare and submit to the government a report that was made public on the condition of the slimes dam.  Four years or so ago I went to the SRK office in Johannesburg.  There was a large space with thirty or so young engineers of every persuasion working on preparation of such reports.  The young Whites, the young Blacks, the young Indians, the young Coloureds (to use South African terminology in its best attitude), the male and female and gay, were all doing what engineers should do:  tame the forces of nature to the benefit of mankind.


Public Disclosure.  All designs, all inspection reports, all qualms and concerns from everybody should be submitted to the public authorities/regulators and soon thereafter made public.  None should be kept secret as is the common practice in BC, but not in Alberta or many USA jurisdictions.  For the only check is public transparency and public scrutiny.  The good old British Empire secrecy based on the believe that there is an upper class and a lower class and that the upper class knows what is best for the lower class, should be dead.  It is not, sadly, dead in BC or for that matter Canada.  My telephone talk today confirmed that my co-talker is committed to the British Empire conviction of the upper classes’ right to decide for the lower class.

Active Lawyers.  I believe in lawyers.   Without them we would not be free or safe.  The more lawyers suing those committed to secrecy, upper-class devotion, incompetence, veniality, stupidity, unprofessional conduct, and so on —the better.   The fear of being sued is the best force to good conduct I know of.  Thus the success of the U.S, system of adversarial conflict as compared to the Canadian, cigar-smoke-filled, room-of-consensus in cleaning up contaminated sites.  Giant Mine and Faro would have been dealt with long ago in an adversarial setting.  Instead they continue for decades and billions to fester in closed covens of self-interest.

Lean, Learned Regulators.   I was recently in a meeting with regulators.  There were four-times as many of them as there were of us.  Most had nothing to say or contribute.  They were professional committee queens.  They talked as we smoked outside of the next meeting; they bragged of the many meeting they had to attend.  Not one had a single insight into what the meeting was about.  We need no more, ten million dollar additional regulators.  We need a few lean, learned regulators.  For laws and regulations are essential: they set in stone what we have to do, how we have to act, and what is necessary & appropriate for public safety.  Laws without active, lean, learned regulators are smoke & mirrors.

So be it.  Tomorrow or the next day or the next we will see the report on Mt Polley.  I have here stated what I think needs to be done to prevent future Mt Polleys.  It will be interesting to see if MVV agree.  I suspect the report’s conclusion will be that the failure was unpredictable, unavoidable, and just one of the inevitable statistics of tailings facility failure.  One in four every year or one in a million?  Dirk Van Zyl has said it was one in a million.  I wonder if he will stand by this in the report?  Or will he go with Steve Vick who says that in the goodness of time all tailings facilities will fail and therefore we should strive only to mitigate the impacts of inevitable failure.  By Monday we know, we hope.



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It is late and maybe I should go to bed.  But before I do I am compelled to write about the Mining Association of Canada’s (MAC) decision not to release it rating of the Mt Polley tailings facility compiled just before the failure. Below I repeat what Gordon Hoekstra writes.  He is a pretty intelligent and informed reporter, so read it carefully and consider.  What is all boils down to is this: (more…)

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Today I took the ferry across the bay from Puerto Santa Maria to Cadiz.  Took a bike and rode around the city sea-wall and around the old city center.  It is a great ride around the sea-wall.  It reminds one of the age of some engineering works. For here we have fortifications that have been four hundred years in the making.  I saw forts and castles built three hundred years ago to defend the city from the French, the Brits, and the Dutch, who attacked at different times.

It reminds us that closure of tailings facilities for 100 or even 200 years is but the outcome of the short history of North America, and not something founded in a profound perspective of real long-term history.  Clearly we can build facilities that last four-hundred years.  The people of Cadiz did.

True defense of their small city was a survival issue.  And true that closure of most mine tailings facilities is not anybody’s defense or survival issue.  I accept that social  utility may be the basis of a rejection of a long closure performance period.  But after seeing what I saw today, I cannot accept the reason too often given: we do not know how and cannot do it.




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I have spent the past few weeks in Rota, Spain with my son and family.  The sun shines on the house patio—most times. Athough some days the mist endures all day and it is cold.   Today the sun overcame the mists by about eleven a.m., and it was fun to sit in the sun and read John Grisham’s book The Last Juror.Sometimes I come inside and work on the computer.  I read what is written on Mt Polley and update an EduMine course that I am writing on Risk Assessment, Decision Making, and Management of Mine Geowaste Facilities.  For the failure of Mt Polley tailings facility is the best possible current example of the failure of risk assessment, decision making, and management of geowaste facilities we know of. (more…)

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