At 9.30 p.m. on the 10th April 2013 the northeast wall of the open-cast Bingham Canyon copper mine, the largest man-made excavation in the world, collapsed, sending more than 165 million tons of rock almost 3000 feet (~900 metres) into the centre of the mine.
The collapse damaged 13 shovels, 14 haul trucks, and a number of drills, bulldozers, and graders, but no one was hurt. Creep of the wall had been noted by geotechnical monitoring in February, with slip of around 1 millimetre per day. By the morning of the collapse creep had increased to ~5cm per day and the site was evacuated at 11.00 am (arguably an HSE success story).
Bingham Canyon mine is owned by Kennecott Utah Copper, a subsidiary of Rio Tinto. The mine has produced more copper than any mine in history – about 19 million tons.
On April 16th Kennecott invoked Force Majeure for copper supply. The 2,500 mine workers have been invited to take unpaid leave of book vacation time off. Mining operations could be suspended for up to a year, with between 80,000 and 160,000 tonnes of copper output lost this year. However, as copper inventories are rising (up 190% in LME warehouses since Oct ’12) Kennecott maybe be able to provide some supply from stockpiles if required.
Kennecott produced ~17% of US copper supplies in 2012, with output close to 163,000 tonnes of refined copper (and 200,000 ounces of gold). Last June Rio Tinto sanctioned investment of $660 to extend the life of the mine from 2018 to 2029.