Ok Tedi battles problems

A preliminary consultant’s report on waste management at the Ok Tedi copper-gold mine in the western interior of Papua New Guinea has not provided any solutions to the mine’s environmental problems, and leaves open the possibility that the mine may have to close.

Ok Tedi, managed by Broken Hill Proprietary (BHP-N), is faced with the problem of disposing of a growing mountain of mill tailings from the 83,000 tonne-per-day operation. Tailings had been dumped into the Ok Tedi River, making their way into the larger Middle Fly River, since the mine opened in the 1960s. As a result, the river bed was raised, causing widespread flooding in the river valleys.

The mine also represents a major source of revenue for Papua New Guinea, and the national government, which owns a 30% stake in the mine, would be loath to force Ok Tedi out of production. Toronto-based Inmet Mining (IMN), with 18%, is the other minority shareholder. Ok Tedi provides about 10% of Papua New Guinea’s gross domestic product and about 20% of exports, and is a major employer in the Western Province.

To determine the best means of managing the wastes, Ok Tedi hired consultants, who initially identified four options: continue dredging the rivers; build a storage pond for future tailings while continuing to dredge; suspend dredging; or close the mine.

The preliminary study concluded that waste disposal from the mine would have a greater impact on the environment than earlier assessment work had indicated. Over the remaining mine life of 10-15 years, flooded areas around the river will spread and existing vegetation will die back throughout the flooded areas. Flood-tolerant plants could be expected to replace the dead jungle vegetation in time.

The study noted that, given changes that had occurred in the profile of the river bed, not even mine closure would prevent flooding and die-back problems. Closure would, however, allow the river system to recover more quickly.

Dredging the river creates channels for water flow, which would reduce the volume of water the valley receives, but trials of dredging suggest that the benefits would be “limited,” says Inmet. The other possible intervention, building a tailings pond, would require the mine to use up a large tract of land, probably displacing several riverside communities in the process. The social disruptions are unattractive to both the government and the shareholders.