On Tuesday 27 December 2011 as train carrying 1500 tonnes of copper concentrate was derailed when it attempted to cross a bridge over the Edith River. The bridge had apparently had its foundations washed away by flooding related to Cyclone Grant, and gave way as the train passed over it. Two members of the train crew were airlifted to hospital in Darwin. About 1200 tonnes of the copper concentrate are thought to have been lost.
The remains of the train at the Edith River Crossing. Picture by photographer Michael Franchi.
Copper concentrate is an early stage product of the copper extraction process. It is formed by taking copper ore, grinding it up, and then exposing it to chemicals that bind to copper and float (such as pine oil or long chain alcohols), so that the copper bearing minerals are separated from the rest of the medium. Typically the resultant mix contains about 25-35% copper, as well as a variety of copper and iron sulphides. It is greenish, slimy, toxic and valuable; the 1200 tonnes lost was probably worth about US$6 million (Au$5.9 million).
Copper compounds are extremely toxic, so this level of loss into a natural water system presents a serious threat to wildlife and agriculture. The Northern Territory's Environmental Protection Agency has launched an investigation of the spill, and has warned prosecutions may follow. The owner of the concentrate, mining company OZ Minerals, has stated that it will mount a cleanup operation once it is safe to work in the area. The company hopes that it should be able to recover any material remaining at the derailment sight, and that any material washed away will become to dilute to present a hazard. Copper compounds tend to be foul tasting as well as poisonous, so there is little danger of large animals drinking contaminated water, though there is a distinct danger to organisms that cannot avoid the chemicals, such as plants and aquatic invertebrates, which may then have an impact on animals higher in the food chain.
The prompt adoption of ownership for the situation by OZ Minerals does bode well for the cleanup. OZ Minerals has stated that the lost material is not significant compared to the size of the companies operations, and that it hopes to complete all shipments for export due in the first quarter of 2012 by March 31. Nevertheless the companies shares had fallen by 13¢ by 3pm on the 27th.
The materials were being transported from OZ Minerals' Prominent Hill mine in South Australia to the Port of Darwin in the Northern Territory for export, aboard a train operated by Genesee and Wyoming Australia. It appears that the operator erroneously believed the route was safe after Cyclone Grant was downgraded to a tropical storm. The closure of the line effectively cuts the Port of Darwin off from the rest of Australia, a major problem for exporters; Australia is unique among developed economies in that it is largely dependent on the export of raw materials. The Environment Centre Northern Territory (an environmental group) has expressed relief that the train was carrying copper concentrate, as trains from the Roxby Uranium Mine also use the route. The Chief Minister of the Northern Territory, Paul Henderson (Labor) has announced an official investigation into rail safety in the state, and has said he will accept any recommendations.
The rail link between Darwin and the rest of Australia.