Background:
The Bingham Canyon Mine near Salt Lake City, Utah experienced the largest highwall failure in mining history on April 10th of 2013 when 144 million tons of material literally exploded out of the highwall and rushed to the bottom of the historic mine. As significant of an incident this was, the amazing part was that no one was injured or killed. There were several critical control measures that prevented injuries or fatalities, such as knowing the greatest risk the mine faced and having great geotechnical monitoring systems. Just as important as these measures were, employee communications with tools such as the Target and Response Plan (TARP) and the Daily Manefay Status Updates were also critical. This article discusses the importance and content of these communications.
We knew it was coming:
On February 12th of 2013 the geotechnical engineering department had warned the management that they had observed signs that the mine would likely experience a massive highwall failure, sometime in the future, on a bed of weakness called the Manefay Fault. At the time, they did not know just how large the failure would be or when it would occur. It could be several months – more data would have to be collected to get a better estimate. It was known that the movement rates were smaller than the mine’s previous highwall failures and that it would not fail immediately. The mine had experienced many failures previously and they all followed a trend of building acceleration until the mass went into progressive failure. The Manefay mass was accelerating but had not reached the progressive failure region yet.
Shortly after the potential for the failure was identified, everyone at the mine site was notified through a Geotechnical Bulletin that a potential highwall failure mass had been identified and they were asked to keep an eye on the area and report any unusual events in the area. In the meantime, the Mine Planning team started to evaluate ways to prevent the failure, by either removing rock from the top of the mass or buttressing the toe of the mass.
Before and After Bingham Canyon Mine
Over the next few weeks more physical signs of the movement appeared with cracking on the surface and the geotechnical data showed that the mass was continuing to accelerate at a relatively constant rate. The mine planners were working on plans to prevent the failure, believing that there would be several months to complete the work. On March 19th, a meeting was set to decide on the preferred prevention method, but as the meeting started the Geotechnical Team made an announcement – the failure would likely happen in a matter of six weeks and not six months. This timeframe changed everything and the decision was made that preventing the failure was not an option and that all efforts would towards preparing for the inevitable. During that meeting, many decisions were made regarding how to prepare for the slide such as the need to move offices and even complete buildings away from the failure area but the work on trying to prevent the failure was discontinued. However, one of the most important decision was to create a Target and Response Plan (TARP) so the everyone would know what should be done as we moved closer to the highwall failure.
The first draft of the TARP was completed in just a few days and by the 27th of March was sent out to all employees and contractors that worked at the mine. The TARP was broken down into five trigger levels, each with its own color coding. The trigger levels included:
- Level 0 or Blue – indicated that the highwall was under normal or stable conditions. The mine was already past this level when the TARP was created.
- Level 1 or Green – indicated that a potential significant failure mass had been identified that had low levels of acceleration. The failure was expected in weeks to over a month and mining operations would continue, but monitoring and management of the situation would be increased.
- Level 2 or Yellow – indicated that the failure mass acceleration had started to increase. Failure was expected in days to a week and the operations would be modified to either reduce or close access to critical areas of the mine.
- Level 3 or Orange – indicated that the acceleration had increased to the point it was near progressive failure. Failure was expected within hours to a couple of days. The failure zone of the mine would be evacuated.
- Level 4 or Red – indicated an unexpected acceleration rate or active failure of the mass had occurred. This would result in an emergency evacuation of the pit.
For each level, there was a separate Operations Response, Management Response as well as an External/Security Response. The actual TARP can be seen in the following table. In addition to the overall TARP there were more detailed TARPs for both the Mine Operations and Maintenance teams.
Bingham Canyon Mine – Trigger and Response Plan – March 2013
Keeping Everyone Informed:
Every morning at the mine management team meeting, the first question asked was about the movement of the mass from the day before. After the TARP was created it was decided to share that information daily, will all employees, so that everyone had a sense of the acceleration.
Per Bingham Canyon’s safety standards, no employee had to work in an area that they felt was unsafe. Employees knew that they could request to work in another area of the mine with no repercussions. By sharing the movement of mass and tying that movement to the TARP in a daily status update, workers in the mine had a much better idea of the situation and could make an informed decision as to whether they wanted to work in the mine that day or not. In fact, no one/few, if anyone requested to work in a different area.
In the Daily Manefay Status Updates that were available at the start of each shift, every employee could quickly see what level the mine was at, the amount of movement from the previous day as well as what actions were needed for the current response Level.
At the start of the daily status updates the mine was in Level 1 (Green), but on April 5th the acceleration increased to the point that the level was increased to Level 2 (Yellow). At this point access was limited in critical areas and the operations were modified.
In the early morning of April 10th, the acceleration of the mass increased significantly and the mine went to Level 3 so the pit was evacuated in a planned and orderly manner. At 9:30 pm the Manefay mass failed in an explosive manner, covering the entire floor of the mine with debris. Although the failure acted differently than expected in the way it failed, which damaged and destroyed a significant amount of equipment, there were no injuries or lives lost because we everyone was aware of and followed the TARP.
A year after the landslide the Bingham Canyon Mine Management held a breakfast for all employees to celebrate the fact that the company had experienced the largest slide in mining history with no injuries or fatalities and had returned to full production ahead of schedule. During that celebration, the memory that was most often shared by the hourly employees was the Daily Manefay Status Report. Sharing that information eliminated the rumors and built up trust between management and the entire work force. They knew that management was not hiding information that was important to them and that they were a part of the mine’s success. This trust was critical in the mine being able to recover from the Manefay as quickly as it did as all parts of the operation worked together to recovery from this huge event.
Conclusion;
How often do we focus on our issues in a situation and not think about sharing information that may be important to others or asking for input? The Manefay showed the importance of having a plan and the value keeping people informed to change what could have been one the largest disasters in mining history to a crisis that was managed with good decisions, teamwork and leadership.
If you would like to learn more the critical control measures used before and after the Manefay landslide you can go to my previous LinkedIn articles: #1 Knowing the Greatest Risk, #2 Independent Experts, Black Hats, and Sharing Lessons, and #3 Geotechnical Monitoring Methods. You can also visit my website RiseToTheOccasion.net to read these articles and more. To get the full story, refer to my book, ”Rise to the Occasion – Lessons from the Bingham Canyon Manefay Slide”.
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Robotic Theodolite Prism Network – With these systems, a robotic theodolite continuously scans the locations of a network of prisms that are placed on the high walls of a pit. The location of each prism is tracked over time and the velocity of each prism can be calculated. A single theodolite can track over one hundred prisms, however, the greater the number of prisms the longer it takes the theodolite to scan all the prisms. The following photo shows a robotic theodolite automatically scanning for prisms.
These photos show the before and after view of the bottom of the pit from nearly the same location. For scale, each one of the benches is 50 on the highwall is 50 foot tall.
