Sulphide-bearing tailings from the Ok Tedi mine in Papua New Guinea have begun to turn into acid on the banks of the Middle Fly River, confronting thousands of villagers with a major environmental crisis.
This development creates the prospect of worsening environmental impacts following dieback problems affecting 15-hundred sq km of forests that could persist for some 200 years.
Overseas experts suggest severe acid rock drainage could be an even greater long-term environmental hazard that could have devastating impacts on the local ecology without preventive measures.
Ok Tedi Mining Ltd managing director Keith Faulkner says numerous studies are being carried out on ways to tackle the problem and mitigation costs could be as high as 100 million-US dollars.
Options will be explained to villagers next year so they can decide if mining should be halted or allowed to continue, a dilemma they had also faced five years ago under the previous operator, BHP Billiton.
Mr Faulkner says significant environmental damage from acid rock drainage was only likely under certain climatic conditions such as during long dry spells.