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Project Manager : June July 2011
21 www.aipm.com.au Project Manager COVER STORY • W hen BHP blasted away a section of the wall of Koolan Island main open pit mine in 1993 to allow the ocean to flood in, it would have been difficult to believe the mine would ever be operational again. Less than two decades later ROCK Australia Operations Manager Mike Moore was handed the task of turning back the seas, draining the mine and providing access to its valuable high-grade iron ore. Between 1959 and 1993, BHP had taken almost 70 million tonnes of hematite from the remote site off the northern Kimberley coast of Western Australia. When it closed its operations, BHP allowed 10 billion litres of seawater to flood in as part of the island’s rehabilitation process , leaving the coral, marine life and the tiger sharks that remain today to claim the pit. However, 67.7 million tonnes of iron ore remain underground, and Mount Gibson Iron recommenced mining on Koolan Island, which has four deposits, in 2007. ROCK was brought on board to drain the 100-metre deep waters and rehabilitate the main pit, a task that would demand innovation and a number of world firsts, including the use of remote control drill rigs operated from floating barges. “This project is unique in many ways – the proximity to the ocean, and the fact that ultimately they will be mining below sea level,” Moore said. “Normally in a new mine you are working from the floor of the pit. Here, we were going to be working from water.” He added that the continuous nature of the pit wall, without ‘benches’ or ledges on which to work from and collect debris, made the reclamation job even more difficult. “I think we can safely say it’s probably the most complex mining geotechnical project ever undertaken. When you throw in the water, it really does complicate issues.” Innovative approach “In terms of the products we are using, there are a number of world firsts,” Moore continued. “ We’re building three debris flow barriers, one of which is the largest ever attempted in the world. It’s also the largest scale mesh job in any mining environment in the world.” Moore’s main material supplier, based in Switzerland, produces the debris flow barriers, which are normally used in alpine environments where melting snows and glacial waters can create massive landslides. ( PHOTO:SHUTTERWORKSPHOTOGRAPHY
April May 2011
Project Manager Aug Sep 2011