What Happens When I Respond to an Emergency (Part 1)

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A website provides a database of world-wide tailings dams failures from 1915 to present (https://worldminetailingsfailures.org/).  That website indicates that they support global research in tailings failure root cause, loss prevention and trend analysis.  Their database lists the following TSF failures that have resulted in more than 100 deaths: 

FACILITY                                                    COUNTRY      YEAR       DEATHS

Mir mine, Sgorigrad                                      BULGARIA      1966         488

Los Cedros, Tlalpujahua, Michoacán             MEXICO         1937         300

Prestavel Mine – Stava, North Italy, 2, 3         ITALY             1985         269

Lixi Tailings Dam (Tahsan Mining Co.)           CHINA            2008         254

El Cobre Old Dam                                        CHILE             1965         200

Huogudu, Yunnan Tin Group Co., Yunnan      CHINA            1962         171

Aberfan, South Wales Colliery                       U.K.                1966         144

Buffalo Creek, West Virginia                         USA                1972         125

Hpakant, Kachin state                                   MYANMAR     2015         113

The database hasn’t been updated to include Vale’s latest failure in Brazil. 

The devastating consequence of a catastrophic TSF failure is obvious. 

Fortunately, some of the best minds in the world are involved in the design, construction and monitoring of tailings dams, and the mining industry is leading the way.  I realize that this sounds like false positivity, given the horrible failures in the past few years, but I am quite positive that in this post-Mount-Polley world, things will get better. 

Okay, back to the topic.  I can relay to you one example of my response to an emergency call.

A colleague was at a mine site in Latin America, completing an environmental assessment.  Their TSF started showing signs of distress, so my colleague contacted me, and off I went.  Upon arrival, the conditions and chronology of events were explained to me.  A visit to the TSF revealed that there was a failure of the embankment, but a very narrow portion of the crest had been preserved.  Fortunately, the surface water pond was at a considerable distance from the dam crest.  

The in-country expert advised the owner to place fill on the embankment so that the crest of the dam could be reestablished.  In fact, he indicated that the fill should consist of cemented soil.  The owner’s team had tried on several occasions to place fill, but each time they made any progress, further slippage occurred. 

I directed them to halt the filling activity and began gathering the information I would need to conduct a “back-analysis” of the failure, so that I could develop best estimates of soil strength parameters.  [A back-analysis is rather akin to reverse-engineering.]  Together, we decided to evacuate the villagers who were residing below the TSF.  I had the owner gather all of the available design documents so that I could establish an accurate pre-failure cross-section profile of the dam. 

The facility had been designed and expanded in several construction campaigns over the years.  Most of that was represented in the various design reports that had been provided to me.  However, there was a relatively detailed cross-section of the TSF dam on one of the engineer’s whiteboards that varied drastically from the design.  I was told that the design on the whiteboard was a good representation of what had actually been built.  This is a good place for me to get on my soapbox and remind everyone of the tremendous value it is to have the design engineer on site during construction and for a set of “as-built” drawings and a “record-of-construction” report to be developed so that these design changes don’t disappear with a swipe of a dry-erase eraser. 

With all of the information collected, I began to develop a slope stability model.

More next time!  

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