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Rise to the Occasion by Brad Ross

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Category Archives: Critical Control Series

Target & Response Plans – Sharing Critical Control Measures #4

Rise to the Occasion by Brad Ross avatarPosted on July 12, 2017 by Brad RossJuly 12, 2017

Target & Response Plans – Sharing Critical Control Measures #4

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

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.

Response Levels Bingham Canyon Mine

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.

Keeping Everyone Informed, Bingham Canyon Mine

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”.

If you liked or found this article useful, please like or share it with others. Add a comment to share your own experiences, have a question or want to know more about an article. Topics for future articles are influenced by these comments.

Posted in Critical Control Series, Geotechnical

Sharing Critical Control Measures #3 – Geotechnical Monitoring Methods

Rise to the Occasion by Brad Ross avatarPosted on June 9, 2017 by Brad RossJune 9, 2017

Rise To The Occasion
This is the third in a series of articles that share some of the critical control measures learned from the largest highwall failure in mining history – the massive Manefay Slide at the Bingham Canyon Mine in 2013. This article discusses types of geotechnical monitoring systems including those that were used at Bingham Canyon to predict the failure nearly two months before the event. The early warning provided by this monitoring was a key critical control that prevented injuries and fatalities that could have occurred in this immense event.

There are several methods to monitor geotechnical movement or changes in open pit mines. Some of these methods are low tech and based on human observations, such as having all employees go through geotechnical hazard training so they can detect and report geotechnical problems as soon as they are observed. Others are extremely high tech – involving sophisticated measurement systems. In the case of the Bingham Canyon landslide, some of the earliest indications of a problem were first observed in the field by engineers and operators. However, to determine the size, scale, and timing required high precision radar systems. This article describes and compares 16 methods of geotechnical monitoring. A robust geotechnical monitoring program normally requires multiple systems – depending on the size of the operation, complexity of the geology, and amount of risk for geotechnical failures.

A summary of the various monitoring methods can be seen in the table “Geotechnical Monitoring Method Comparison”. This table compares the various monitoring methods based on the following seven qualifiers:

  • Measure – What does the system measure? Ranges from observation to amount of movement.
  • Type – Is the measurement taken at a point, over an area or a linear distance?
  • Geometry – Is the measurement made on the highwall, on top of the surface or within the subsurface?
  • Continuous – Is the measurement taken continuously or intermittently as needed?
  • Portable – Is the monitoring system portable and easily moved or based in a fixed location?
  • Initial Cost – Is the initial cost relatively low (thousands) or high (hundreds of thousands of dollars)?
  • Alarmed – Can the monitoring be alarmed to initiate an evacuation of the mine in case of exceedance?

Geotechnical Monitoring Method

The field of Geotechnical monitoring is a critical control measure designed to keep miners safe. This is a field that continues to rapidly expand and improve. New technologies, such as radars and laser scanners, continue to be introduced on a regular basis. If you are aware of new geotechnical monitoring technology, please share with the author so that this table can be updated.

Geotechnical Monitoring Method Descriptions
Following is a short description of each monitoring method along with the key advantages and disadvantages of the method.

  1. Geotechnical Monitoring Method

    Geotechnical Hazard Training – This method trains employees that work in the mine how to identify geotechnical hazards and what to do if a hazard is observed. This method has a low upfront cost since it is usually part of the required MSHA or other required safety training. The key is to have the procedures and expectations in place for all employees to report and act upon hazards, including the authority to stop operations if a serious issue is detected. The following photo shows dust from falling rock, which is one of the geotechnical hazards that miners are trained to look for and report.

    Advantages: Employees are typically in all parts of the mine and are familiar with normal conditions so they can detect changes or unique situations that other monitoring systems may not detect. Bingham Canyon had 800 pairs of trained eyes looking for geotechnical problems.

    Disadvantages: There are periods when employees are not in an area and therefore changes may not be observed. This method is qualitative and small changes may not be noticed or reported.

  2. Documented Inspections – Like Geotechnical Hazard Training, this method relies on observations, but in this case observations of professionals such as trained geotechnical engineers, mining engineers, geologists and supervisors.

    Advantages: Inspections are performed by a professional who has a higher level of knowledge and understanding of geotechnical hazards. As part of the inspection, the amount of movement or risk for failure can be further quantified with professional observations and measurements.

    Disadvantage:  The intermittent inspections are usually performed once per shift or per day and therefore changes would not always be detected in real time.

  3. Synthetic Aperture Radar

    Synthetic Aperture Radar – Geotechnical radar systems can detect very small levels of movement or velocity changes over a large area on the surface of highwalls, in near real time. The radar systems can then be used to trend the movement over time to help predict failures or alert operations of impending highwall failures. Synthetic Aperture Radar systems have typically been semi mobile and placed in a fixed location for relatively long periods. These systems are set up to scan large areas of a pit from long distances (over 2 miles away). The following photo shows a synthetic aperture radar system in operation at the Bingham Canyon Mine.

    Advantages: The fixed system acts like a sentinel, watching over a large area and reporting changes and potential hazards. The Bingham Canyon mine used Synthetic Radars to help determine the size of the Manefay and the fact that the slow-moving mass was actually accelerating and headed towards failure.

    Disadvantages: Fixed radars are line of site and any areas screened from the radar will not be monitored. In addition, as the monitored area is increased, either the data resolution is decreased or the time between scans is increased, resulting in less information for the entire area.

  4. Real Aperture Radar  – These systems have many of the same attributes of the stationary synthetic aperture radars, but are normally mounted on trailers or trucks. If a problem is detected, the radars are moved closer to areas of concern. The photo at the top of this article shows a real aperture radar system monitoring the Manefay scarp at the Bingham Canyon Mine.

    Advantages: Since they are closer, a smaller area is monitored with a higher resolution with shorter times between scans. This provides excellent monitoring of troubled areas that are of high risk of failure.

    Disadvantages: Mobile systems cannot be relied upon to continuously monitor large areas. If the mobile system is moved to monitor a problem area, then larger areas of the mine would not be monitored and protected.

  5. Robotic Theodolite Prism NetworkRobotic 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.

    Advantages: Robotic theodolites measure the movement of a specific point so it is simple to trend the movement and acceleration over time for each point. Radars on the other hand measure broad areas instead of tracking specific points, so calculating trends and cumulative displacement is more problematic.

    Disadvantages: The scattering of points may not reveal movement of smaller blocks and the movement of a few points may not be representative of an entire area. Also, there may be slight errors in the data due to diurnal or weather changes. Although these errors average out over longer time periods, velocity calculations can be influenced in the short term.

  6. Surface Extensometers – One of the oldest methods of geotechnical monitoring is the use of extensometers to monitor changes in surface cracks. Modern surface extensometers often use a cable reel anchored to one side of the crack with the cable stretched and anchored across the crack. Any movement will pull cable from the reel, which is measured and automatically recorded. Unusual movement can then be detected and appropriate personnel alerted. The following photo shows a extensometer set up at the Bingham Canyon Mine.

    Surface Extensometers

    Advantages: This system is a relatively simple and inexpensive way to monitor surface cracks that can be precursors to a problem. Measurements are in real time and if an unusual movement is detected an alert can be automatically sent.

    Disadvantages: A crack may not be identified or accessible and thus cannot be monitored with this method. Surface extensometers also monitor only a single point and are subject to error as temperature changes impact the length of the cable.

  7. Time Domain Reflectometry

    Time Domain Reflectometry (TDR) – A TDR is a co-axial cable that is extended down a drill hole and then attached to an instrument that sends an electric pulse down the cable. The instrument can detect if there has been any distortion or changes in the cable and the location of that distortion. If there is any earth movement down the hole, the TDR can detect the location and indicate relative magnitude of that movement. However, the amount of movement is not quantified with the TDR. The following figure is an example of data from a TDR over a five month period. The small tick marks show when movement is detected on the top of Bed 1 beginning on March 17 and the movement continues to increase over time. The values in the tick marks show the change in impedance and not displacement.

    Advantages: TDRs monitor subsurface movement; are relatively inexpensive if installed in holes drilled for exploration or piezometers; and the entire length of the drill hole can be monitored.

    Disadvantages: TDRs do not record the actual movement in the drill hole and the readings are often taken manually (although the process can be automated).

  8. Piezometers – Water pressure is a critical aspect of rock stability and piezometers are used to measure water levels and pore-water pressure, critical aspects to rock stability. Often water pressure is not studied until there is already a geotechnical problem, which is too late.  Vibrating wire piezometers can be installed in a drill hole at either single or multiple locations to monitor changes in water levels and pressure. The data from these monitors are critical in calculating the stability of the highwall. The following photo shows a drill hole with sensors whose data is automatically sent to a central location.

    Advantages, Although piezometers do not measure ground movement, they can be a key leading indicator of a potential problem by measuring changes in water levels.

    Disadvantages: Piezometers only measure pressure at the hole location. The water depth and pore pressure of perched water tables or geologic irregularities may be missed if piezometers are not placed in those locations.

  9. Microseismic Monitoring – A microseismic monitoring system uses geophones or accelerometers that detect seismic energy (the sounds of rocks moving underground).

    Advantages: Multiple Microseismic monitors can be used to determine the location of underground earth movement in 3D space with triangulation.

    Disadvantage: Unfortunately, the processing requirements are so extensive in these systems that they have been more useful in determining the location of movement afteran event. Additional research with this method could improve its usefulness.

  10. GIS Data Display – The geographic information display (GIS) allows the information measured by the various monitoring systems to be stored on a network server and then displayed at any location in the network. Often this information can be combined with data from multiple sources to help geotechnical engineers detect/determine trends and understand changing situations.

    Advantages: GIS Data Display systems make other measurement systems useful and effective.

    Disadvantages: These systems depend on networks which may have reliability issues at some locations.

  11.  Drone Photogrammetry – One of the fastest growing monitoring methods is the use of aerial drones to take high resolution photos anywhere in the mine. With these photos, engineers can observe conditions of the entire mine. By using photogrammetry, changes in surfaces can be detected and measured from the photos.

    Advantages: Drones can safely get information from inaccessible or dangerous areas.

    Disadvantages: Post processing time does not allow for real-time monitoring and alerts. This disadvantage should improve as the technology matures.

  12.  GPS Prism System – similar to a robotic theodolite prism network, the GPS prism system tracks the movement of individual points on highwalls and benches using satellites instead of theodolites.

    Advantages: GPS do not rely on line of sight like a theodolite, (although their signal can be blocked at times).  Also, true movement vectors can be calculated to determine/improve the understanding of the mechanics of a failure mass.

    Disadvantages: GPS prism system cost per point is more expensive than a theodolite prism system and results are not as accurate. These systems also rely on a base station to adjust for induced errors in GPS signals. This limits the distance that the GPS prisms can be located from the base station. There are times that GPS satellites are not available so the GPS system is not operational.

  13. Downhole In-Place Inclinometers – Sensors are placed in drill holes to monitor ground movement as well as the direction of movement. Often multiple sensors will be placed in a single drill hole to better determine the location of movement.

    Advantages: The direction and amount of underground movement can be measured continuously and an alarm can be set for when unusual movement is detected.

    Disadvantages: Movement is only measured at specific points in a drill hole.

  14.  InSAR – (Interferometric Synthetic Aperture Radar) uses radar from orbiting satellites to scan the surface, which are then compared to previous scans to calculate the amount of movement in any area.

    Advantages: InSAR originates from space so there should be very few areas that are not in line of sight.

    Disadvantages: InSAR is only available when the right satellites are overhead and the significant amount of postprocessing time. This system is good for developing an understanding of overall movement, but not practical for real time monitoring.

  15. Laser Scanner – laser scanners have the same benefits as radar systems. They can be configured for continuous monitoring of highwalls and set to send alerts if a problem is detected. They can be set up at either portable or fixed locations.

    Advantages: Many mines already own laser scanners for planning purposes and the data can be used for multiple purposes.

    Disadvantages: Lasers are impacted by dust and precipitation. During significant events, it may be difficult to gather data.

  16. Downhole Inclinometers Probes – unlike in-place inclinometers, these probes measure the changes in the diameter of a drill hole that has been fitted with special tracks for the probe to follow. The shape of the drill hole is compared to previous scans to determine if any movement has occurred.

    Advantages: This system measures movement along the entire length of the drill hole and it is relatively inexpensive for initial cost

    .

    Disadvantages: Scanning is generally performed manually. The time required for post processing of the data prevents real time monitoring and alerting capabilities.

Conclusion
Because of the significant risk and impact of geotechnical events in the mining industry, there is a demand for monitoring methods to continue to expand and improve. Each mine has its own unique circumstances and therefore may require a unique combination of monitoring methods that meet those circumstances. Additional information can be found in my book, Rise to the Occasion – Lessons from the Bingham Canyon Manefay Slide.

To see other articles in this series go to Sharing Critical Control Measures #1 – Knowing the Greatest Risks or Sharing Critical Control Measures #2 – Independent Experts, Black Hats, and Sharing Learnings. You can also visit my blog for these and other articles at RiseToTheOccasion.net.

If you found this article on geotechnical monitoring methods to be useful and/or interesting, please like or share with others. The genesis for this article was the result of a comment from a reader that was posted in an earlier article – so your comments make a difference.

All photos in this article come from the book Rise to the Occasion – Lessons from the Bingham Canyon Manefay Slide and are copyrighted by Rio Tinto.

Thank you.
Brad Ross

Posted in Critical Control Series, Geotechnical

Sharing Critical Control Measures #2 Independent Experts, Black Hats and Sharing Learnings

Rise to the Occasion by Brad Ross avatarPosted on March 30, 2017 by Brad RossMarch 30, 2017

In this second article of my series of Sharing Critical Control Measures, I discuss the importance of three critical control measures to help prevent unexpected “Black Swan” events, including:

  • Using independent experts.
  • Challenging the basic assumptions of experts (wearing a “black hat).
  • Sharing learnings to prevent similar events.

At 144 million tons, the Manefay Landslide at the Bingham Canyon Mine in 2013 was the largest in mining history. As noted in my article “Sharing Critical Control Measures #1 – Knowing the Greatest Risk”, the geotechnical team did a fantastic job of predicting the failure nearly two months before it happened, resulting in the planned evacuation of the mine, which prevented loss of life and injuries. However, predicting how the Manefay would fail did not go nearly as well, resulting in damaged and destroyed equipment. Manefay Landslide at the Bingham Canyon Mine

Before the Manefay, all of the mine’s highwall failures followed a typical wedge or circular failure model. The mass would start to accelerate over time until it would go into a “progressive” failure state. The acceleration of the mass would increase exponentially, ending with the highwall losing its structural integrity and a frictional rock slide would take place. In a matter of hours or days the mass would move downward until it achieved the rock’s natural angle of repose. At that point the mass would be stable and stop moving.

The Manefay was different. Although it began accelerating like all the previous failures, when it went into progressive failure, it ultimately failed in a catastrophic event. At 9:30 pm on April 10, 2013, the accelerating mass literally exploded out of the highwall. Instead of taking hours or days, tens of millions of tons of rock flowed like an avalanche (volellmy properties versus frictional properties) nearly 1 ½ miles to the bottom of the pit – in just 90 seconds. To make matters worse, an hour and 35 minutes later, a second episode occurred and once again tens of millions of tons of rock exploded out of the highwall and flowed into the bottom of the pit, just like the first.Manefay Landslide at the Bingham Canyon Mine

The way that the Manefay failed was a surprise as it traveled much further and faster than anticipated. Anything in the path of the enormous mass was either destroyed or was simply picked up and shoved out of the way. This resulted in the damage and destruction of three large mining shovels (including a P&H 4100C), thirteen 320 ton haultrucks, three drills as well as a multitude of spare parts, support equipment and supplies. The photo shows one of the haultrucks that was shoved by the slide, as shown in the opening photo of the article.Manefay Landslide at the Bingham Canyon Mine

We knew a portion of the only haulroad going into the mine would be destroyed. Therefore, the plan was to be able to quickly resume mining ore and sending it to the inpit crusher and conveyor after the failure. To achieve the plan we stationed equipment and supplies on and behind the “Moly dome” which was 300 feet above the bottom of the pit and away from the Manefay mass. But because the failure traveled so fast and far it not only covered the Moly dome, it deposited another 300 feet of debris on top of it. The results of the failure were clearly not anticipated.

Manefay Landslide at the Bingham Canyon MineThese 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.

So how is it that a geotechnical team that did such a great job of predicting the failure could be surprised with how it failed?

Unlike all previous highwall failures at the mine, the Manefay was an active/passive block failure instead of the typical wedge or circular failure. This, and the fact that the Manefay was so large that it built up a tremendous amount of pressure, resulting in the force needed to propel the rock out of the wall, defying expectations. The technical experts had relied on their extensive experience and understanding of the typical failures at the mine when planning for the Manefay and did not consider other failure mechanism scenarios. The Manefay could be classified as a “black swan” event, as described by Nassim Nicholas Taleb in his 2012 book, The Black Swan: The Impact of the Highly Improbable. Per Taleb, a “black swan” event is one that is unexpected, has a major impact and is the first recorded instance (but is often rationalized that it could have been expected, even if it couldn’t). The Manefay fits these criteria since the way it failed was unexpected, it had a major impact to both the Bingham Canyon operations as well as the mining industry understanding of possible failure modes, and there was no documented highwall failure avalanche events having occurred in open mines.

This leads to the next question – if the way the Manefay failed is classified as a black swan event, what critical control measures can be used to prevent or at least anticipate such events?

A black swan event is only a black swan because no one considered the real possibility of the event occuring. The first critical control measure that could have been implemented before the Manefay is the use of independent experts to review work on critical issues. We knew the Manefay was larger than the historic failures at the mine and it was acting differently than any previous failures. But we were confident in our knowledge and understanding of failures at the mine and relied on our own extensive experience to analysis the potential outcome. The use of independent experts could have increased the breadth of experience and understanding of different failure modes. In addition, independent experts may not have been blinded by the previous successes and biases of the operation. However, it is not a given that independent experts would have actually made a difference in anticipating the ultimate failure mode.

After the Manefay, the mine created and relied heavily on a team of independent experts called the Mine Technical Review Team (MTRT). This team reviewed the geotechnical analysis and remediation plans before we progressed on each phase of that work. The MTRT challenged our basic assumptions and were key to the success the mine had in quickly and effectively recovering from this massive event.

The second critical control measure is for leaders in the company to challenge the assumptions and work of technical experts (or “wear a black hat” as Edward De Bono describes in his book “Six Thinking Hats”). This can be difficult but essential to do in situations like the Manefay where the geotechnical team did such a good job of predicting the failure, but were still faced with conditions that they had never experienced before. I think about myself, coming in to lead the mine planning team, just six weeks before the failure and being so impressed that the geotechnical team had found the Manefay in the first place, that I did not question the analysis or conclusions. However, I was the perfect person to question or “wear a black hat”, since I did not have as the same history, experiences or preconceived expectations as other people in the company. Wearing the black hat should not be looked at as being judgmental or not trusting, it is just one more important critical control measure designed to keep people safe.

Although the first two methods may or may not have made a difference to the outcome, the third critical control measure, which is sharing and documenting our experiences about critical learnings, is the best way to prevent black swan events. Unfortunately, these learnings may be the result of experiencing a black swan or traumatic event, but sharing what is learned is a way prevent others from experiencing the same fate.

To the credit of Rio Tinto/Kennecott, they took the position of sharing what they experienced, to benefit the entire industry. There are other examples of companies sharing their learnings of large scale events such as the investigation reports from BHP/Vale in the Fundão Tailings Dam Investigation Report or Imperial Metal’s Mount Polley Investigation Report. However, not all parts of the industry are as willing or able to share what they have learned. If our industry is going to continue to improve its safety record and prevent large events, we must learn from each other and share both the good things we do as well as the hard lessons. That is the purpose of this series of articles. In addition of the University of Arizona, through the Mining Engineering and Public Health Departments, is evaluating ways to capture and document these critical control measures and learning to be shared throughout the industry. Please consider sharing your experience so we might all learn without going through a crisis.

Posted in Critical Control Series

Sharing Critical Control Measures #1 Knowing the Greatest Risk

Rise to the Occasion by Brad Ross avatarPosted on March 14, 2017 by Brad RossMarch 14, 2017

This is the first in a series of articles intended to share some of the critical control measures that were used at the Bingham Canyon Mine to keep people safe from the largest mining highwall failure in history – the massive Manefay slide. Critical control measures are the equipment, systems, procedures, and policies that an organization uses to prevent injuries and death. The hope is that by sharing the critical control measures from actual situations (like the Manefay), that others can use the same methods to keep people safe.

The Manefay happened on April 10th of 2013, when 144 million tons of material literally exploded out the highwall and traveled nearly 1 ½ miles – filling the bottom of the pit with 600 feet of debris. This failure happened in two episodes, each taking just 90 seconds from start to finish. The failure destroyed equipment and severely damaged the mine – but there were no injuries or fatalities because the mine had already been evacuated.

The first critical control that kept people safe during the Manefay is that Kennecott Utah Copper understood that highwall failures were the single greatest risk to people at the mine. This was based on their experience of having literally hundreds of much smaller failures over the mines 107-year history. Because they understood this risk, they invested in 10 different methods to monitor the highwalls and predict potential failures. The mine considered these methods as levels of protection so each is a critical control method and included:

  • IBIS Slope Stability Radar
  • GroundProbe Radar
  • Geotechnical Hazard Training
  • Routine, Documented Inspections
  • Prism Network
  • Extensometers
  • Time Domain Reflectometry
  • Microseismic Monitoring
  • Geographic Information System Data Display
  • Piezometers

After the Manefay, Bingham Canyon added two additional systems that included a global positioning prism system and downhole inclinometers.

Critical Control Measures

Critical Control Measures

Because of the monitoring and the skills of the geotechnical team, the Manefay was predicted nearly two months before it actually occurred. This allowed the mine to prepare for the eventual failure by keeping people informed, moving buildings/infrastructure, implementing a response plan and ultimately evacuating the mine before the highwall failure.

Finding and predicting the Manefay took a combination of tremendously high-tech radar systems as well as human field observations to be successful. Relying on just one method or even two monitoring systems may not have provided the information to keep people safe. More detail will be given on individual methods in the future.

Special thanks to Kennecott Utah Copper and Rio Tinto for being willing to let me use their photos and share the critical controls and other learnings in my book “Rise to the Occasion – Lessons from the Bingham Canyon Manefay Slide”. Their willingness to let others learn from the Manefay is impressive.

In future articles, I will take more examples from the book about these and other critical control methods that were used before, during and after the Manefay. If you want to learn more, please follow me on LindedIn or go to my website risetotheoccasion.net.

If you believe it is important to share critical control measures such as these, consider liking or sharing this article, or better yet, share some of your critical control experiences in the comments.

Posted in Critical Control Series, Geotechnical
©2019  &nbsp90 Degrees Consulting    Brad Ross, PhD, PE    brad.ross@risetotheoccasion.net   Tucson, AZ
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