On April 10th this year, one of the world’s largest landslides tumbled 150 million tons of rock and dirt down the northeastern pit wall of Kennecott Utah’s Bingham Canyon copper-gold-molybdenum mine, likely becoming one of the more expensive landslides in modern history.
The U.S. Geological Survey estimated that the landslide unleashed 128 million cubic yards of rock and dirt into a pit nearly a mile deep, equal to about two-thirds of the material removed for the construction of the Panama Canal. Put another way, however, the largest landslide in modern history, the 1980 Mount St. Helens eruption, loosened 3.7 billion cubic yards.
Perhaps the biggest victory of this event was the ability to forecast and plan for it. Pit wall movement for the 24-hour/7-days-a-week operation was first detected in early February. A combination of radar, prisms and geotechnical sensors was employed to gather data used in mine planning. Mine employees were trained to observe and make slope stability determinations in areas that impacted their work.
By April 10th the accelerated trend of the slide had reached a velocity value of 2 inches per day; all mine personnel were evacuated from the area surrounding and below the slope. The slide occurred at 9:30 p.m. that evening.
Despite the extensive monitoring and data gathering, the size and travel distance of the landslide was not anticipated. The first slide was predicted; however it generated a second event which traveled further into the pit than expected—both events unfolded over a 20-30 minute time period.
Jobs, buildings and heavy equipment were lost; however, the 350 employees who normally work the night shift had been previously evacuated and were safe. “Nobody was hurt. That was a very big deal for us,” said Kennecott spokesman Kyle Bennett
However, three shovels out of a 13-shovel contingent, 14 trucks out of a 100-truck fleet, and ancillary equipment including drills, bulldozers and graders were damaged or buried by the slide.
Limited operations resumed the next day on the southeast portion of the mine that was not impacted by the fleet. The in-pit crusher and conveyers were not damaged but the primary access road to the operation was destroyed. A hair-pin corner of a secondary road had to be fixed before safe access to the pit was viable.
In what was probably the first use of a corporate Facebook page by a global mining company for emergency communications, Kennecott launched in-house, daily news coverage on Facebook of the landslide from April 11th. Numerous photos of the slide and its impacts were posted by Kennecott on the website flickr.com to ensure unfettered media access. Videos have been posted by the company on the website vimeo.com
In an interview Thursday with Mineweb, Kennecott spokesman Kyle Bennett estimated one million people worldwide are now part of Kennecott’s social audience, thanks partly to a Facebook page that was only one-year old when the landslide occurred. “We elected to drive the dialog” and made sure we were “on early and on often,” he observed.
FISCAL IMPACTS GO BEYOND KENNECOTT
Within 16 days of the event, Kennecott was mining new ore from the pit at reduced levels. A five-mile conveyor belt and an in-pit crushing system now transport some of the ore. Nevertheless, this year’s production is expected to be halved.
Perhaps the most intriguing strategy employed at Bingham Canyon is converting 20 pieces of heavy equipment to remote control to assist in clean-up of the slide. The robotic equipment is used to get closer to the slopes to move dirt and rock. “It allows us to do the really critical work here in the mine where we are…not putting our people in a dangerous situation,” Bennett recently told Salt Lake City television station KUTV.
Despite paying $150,000 for each conversion to robotics, Kennecott says the investment is worth it to clean up the slide and to get Bingham Canyon back on track.
Kennecott’s state-of-the art smelter lost some feed, but the company has purchased small amounts of concentrate, as well as utilized stockpiled ore, to help compensate.
Cash cost impacts on the smelting operations and mining operations are not yet known.
Initially, to ease the impact on workers after the slide, Kennecott asked them to take vacation and voluntary time. The United Steel Workers union negotiated early retirements and other plans.
Bennett told Mineweb 130 employees out of 270 workers chose the one-time retirement incentive of $20,000 per person.
Some work reassignments took place across the operation including 34 smelter and concentrator workers who were offered jobs for comparable pay at the tailings pond and the mine, Wayne Hollands of the United Steelworkers told the news website KSL.com.
The number of salaried employees, mostly supervisory, had been reduced by 100 in May by Kennecott. Initially it was feared the company was looking at a 35% reduction in its workforce.
At least one contractor, mining construction company Cementation USA, laid off 45 miners in April. The company was digging tunnels as part of a mine life expansion project, KSL.com reported.
The financial impacts of the landslide may also go well beyond mining. By 2015 Salt Lake County, local schools and a fire district may lose a portion of tax revenue paid by Kennecott Utah Copper—estimated at $53 million last year, Salt Lake County CFO Darrin Casper told KSL.com.
Even high-end jewelry retailer Tiffany & Co. may eventually feel the impacts of the landslide. Tiffany purchased about half of the total silver mined at Bingham Canyon in 2011. Tiffany buys from Kennecott partly because of their mutual commitment to sustainable development and responsible mining. In a March 2012 interview with the Deseret News, Precious Metals, Copper Group Vice President of Marketing, Vania Grandi, said 400-ounce gold bars and 1,000-ounce silver bars are produced by Kennecott and shipped to Tiffany & Co.
University of Utah geologist Jeffrey Moore recently observed that the main lesson to be learned from the Bingham Canyon landside “is that large rock slope failures like these are not unpredictable.”
“They typically show many precursory warning signs, and with the right monitoring system and proactive approach, the time of failure can be forecasted with reasonable accuracy. This is a real success for the mine and a lesson to others in the community,” he stressed.
In a blog published April 16th, Dr-Dave, aka Dave Petley, Wilson Professor of Hazard and Risk in the Department of Geography at Dunham University in the United Kingdom, wrote, “In landslide terms this even was a major success, with one substantial caveat, in that the detailed monitoring allowed the event to be predicted, which meant that the mining operations were stopped and the mine was evacuated prior to the event.
“Interpretation of the movement patterns can be used to forecast and even predict a failure vent,” he observed. “I suspect we need to undertake more research on the ways that we can extract this sort of information from these datasets—my colleagues and I have also been working in this. It would be fascinating to back analyze the dataset from this event to see if we can develop better techniques”.
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