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46 E&MJ; • MAY 2014 www.e-mj.com S LO P E S TA B I L I T Y Recovering from Bingham Canyon's Record-setting 2013 Slide Rio Tinto's Utah copper operation rebounded rapidly to regain full production By Russell A. Carter, Managing Editor When a massive slab of material high on the northeastern wall of the huge Bingham Canyon open-pit copper mine broke loose last year, it was probably the least-unexpected event to occur in the mine for some time. Geotechnical per- sonnel at the northern Utah mine, owned by Rio Tinto and operated by Kennecott Utah Copper (KUCC), had been monitor- ing ground movement in that part of the pit, known as the Manefay fault area, for months; meanwhile, mine operations teams had identified areas of possible major impact in case of a slide and had developed an escalating set of "threat levels" to limit or halt access to the mine in response to worsening conditions. By February 2013, the mine knew from ground-movement data—collected from a 220-prism network, extensome- ters, time domain reflectometry, micro- seismic array, IBIS and GroundProbe slope stability radars—that a slide was inevitable and imminent. What surprised everyone, when it finally occurred at 9:30 p.m. on April 10, was its overall size and scope, involving an estimated 147 million tons of material that buried more than 95% of the pit floor under 100–400 ft (30–122 m) of dirt and rock. In just min- utes, the slide drastically changed the size and shape of the pit, covering much of the exposed ore zones and rendering production plans and schedules almost useless. The slide route extended 2,400 vertical ft (732 m) down the pit wall, cre- ated an escarpment up to 400 ft high at the top of the slide, and left a 20-million- ton block of rock in place on the pit rim, perched on the fault line and subject to failure at any time. It also tore out a 1,500-ft-long sec- tion of the main haul road—known as the "ten percent" road and the only major route in and out of the pit—and buried 13 haul trucks, three rope shovels and 60,000 lb (27, 215 kg) of diesel fuel stored at the pit bottom. It essentially split the production fleet into two groups: equipment that was stranded below the damaged section of the main haul road, and equipment that was located above the damaged road segment. Because of extensive monitoring and preparation prior to the slide, the mine evacuated workers and some equipment from threatened areas well before the dis- aster took place, and no one was injured. The in-pit crusher, crusher ore conveyor, and conveyor tunnel to the Copperton concentrator stockpile shed were undam- This post-slide photo provided by Kennecott Utah Copper shows how the 2013 Manefay slide damaged infrastruc- ture and changed the size and shape of the century-old Bingham Canyon pit in minutes. EMJ_pg46-51_EMJ_pg46-51 5/6/14 2:08 PM Page 46