Tailings and mine waste 2015 (TMW2015) is about to start.

Tailings and mine waste 2015 (TMW2015) is about to start.

Oct 14th, 2015

Tailings and mine waste 2015

At this conference we will present a paper on Tailings Facility Failures in 2014 and an Update on Failure Statistics. In addition we will give a short course on Risk Assessment, Decision Making, and Management of Mine Waste Facilities.

Mount Polley Tailings Dam Breach

Mount Polley Tailings Dam Breach

In the paper we are looking at statistics of tailings dam failures. 2014 reportedly had three major tailings facilities failures:

2015 so far does not have any reported TD failure. However recent record-breaking rains in the Carolinas (last: 9th October 2015) are accentuating problems at Duke Energy dams. The situation is becoming more and more worrisome:

  1. An embankment on the dam at the Belews Creek Steam Station in Stokes County was seeping water.  Belews Creek is a tributary of the Dan River. 
  2. A sinkhole formed at the base of the dam at the Marshall Steam Station on Lake Norman. Lake Norman supplies drinking water for parts of Charlotte and other nearby communities. The sinkhole was on the side slope of a roadside ditch near the dam. Duke Energy responded by excavating the site, placing a liner in the hole and then filling the sink hole with crushed stone.

If no TD major failures would happen in 2015, would this new data alter the historic estimated frequency of failure?

The answer is: not necessarily.

As a matter of fact, if we look at the time window between the year 2000 and 2009 there were 15 serious (major) failures. However, within that same time frame, 2005 and 2007 had no failures fitting the serious (major) criteria.

We can explain and show an example (15 events over 10 years leading to a frequency of 1.5 failures/years) of this by showing the graph below. It displays the probability to see any number of events during a single year. On the vertical axis one reads the probability to see an event, whereas the horizontal axis shows the number of events.

Trailing dam failure probability

Trailing dam failure probability

The probability to see 0 event remains 22% although the frequency is above 1.  For more statistics, proper definitions and TD reliability you have two solutions. Either you come to our paper presentation and our course  at the TMW 2015 or you come back to this website once the conference is over.

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Category: Consequences, Hazard, Mitigations, Probabilities, Risk analysis, Risk management, Tolerance/Acceptability

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