From 1991 to 1996 I was one of the first regionally based Environmental Officers with the then Department of Resources Industries. My regional extended from Bowen across to the Queensland/Northern Territory and all the way the north to the Torres Straits. My role was the regulation of all the metalliferous mines (non-coal mines) in the region ranging from small family owned alluvial gold operations in the Palmer River gold fields to large scale hard rock coal mines around Charters Towers and Bauxite mines on the west coast of Cape York. I was fortunate to work in some of the most remote parts of Cape York and the Gulf of Carpentaria and got to see some spectacular if not incredibly harsh country. Part of my role was rehabilitating derelict mines. The region was riddled with hundreds if not thousands of derelict hard rock and alluvial tin and gold mines as well as base metal mines. This included the derelict mines in the Wet Tropics World Heritage Area from Townsville to Cooktown.
One of the largest derelict mines was on Horn Island in the Torres Straits. Gold was first found on Horn Island in 1894 with the first serious hard rock mining in 1907. Torres Strait Gold Pty Ltd commenced open cut mining on the east side of Horn Island in 1987 and the mine shut in 1989 due to poor gold grades, poor grade control and water supply issues. The Department cancelled the mining leases in 1990 and ceased all of the assets that were auctioned to increase the funds available to rehabilitate the site. When the mine ran out of fresh water they used sea water as process water in the process plant. Not surprisingly this destroyed much of the processing plant substantially decreasing its value to scrap only.
I commenced a comprehensive monthly ground and surface water monitoring program on site in 1992 in order to understand the extent of acid drainage on site and to develop a rehabilitation strategy for the site to minimize the impact of the acid drainage and associated heavy metal contamination on the surrounding fringing reef and fishery. One of the scariest things I had to do was wade through waste level croc infested swamps to collect water samples and download water flow loggers. That was character building stuff well before the days of SWMS and health and safety.
I also commenced consultation with Horn Island residents in order to determine an agreed post rehabilitation land-use for the mine which was extremely challenging given the mistrust for the QLD Government that approved the mine in the first place.
The first phase of rehabilitation was to remove all the toxic chemical from site. That was an adventure in itself given that the only semi-trailer on site was unregistered with no brakes. I can’t tell you the relief when that last drum of Xanthate was loaded on a barge to make its way back to Brisbane for appropriate disposal. The second phase was to remove all the remaining infrastructure from site. The photo is me in front of the old processing plant just before it was demolished and removed from site.
Phase three was capping of the tailings dam and installation of an artificial wetland to treat acid mine seepage from the process water dam and phase four was diversion of Spring Creek into the mine pit to flood the exposed acid producing waste rock in the pit wall to prevent it oxidizing. This worked well with pit water quality returning close to background levels.
When I left the Department there was still a huge amount of work to do including capping the low grade ore stockpile and waste rock dumps which has been partially completed. With record gold prices, two companies Alice Queen and St Barbara have formed a joint venture to explore and potentially mine Horn Island. I can only hope that if the new mine is approved contemporary mining and rehabilitation practices will be employed to resolve the legacy acid drainage issues resulting from the mine.
By Michael Frankcombe,
Associate Director, Land, Water and Rehabilitation
02 9493 9500