Ok Tedi Environment - Impacts
In Chile, where the largest copper mines of the world are operated, waste is just set aside, and will remain in a desert climate for a long time. On New Guinea, the situation is more difficult. Tropical rainfall may wash away any disposals, if not confined by a dam or in a deposit, that is built and maintained as a building. The government of PNG imposed to build a tailings reservoir, and OTML started the construction of a dam south of the mine. However, a landslide damaged the foundation of the dam in 1984. Considering the impact of a sudden burst of the dam, caused by landslide or earthquake, the plan of a tailings dam was dropped without any alternative. PNG government, overriding the advice of its technical staff (see "Smoking Gun Files"), set levels of pollution, that allowed OTML to discharge tailings without any treatment.
On the upper Ok Tedi, coarse rock and sand aggraded the river bed. Ok Mani and Sulphide Creek, just below the dead rock dumpsite, are elevated 50 - 80 m. The Ok Tedi at Tabubil has a river bed elevated 10 - 20 m. Miners never miss an occasion, to mention the landslides in the mountain areas, that may fill a river bed in an instant. However, the singular landslides must not be compared to the steady dumping of mine waste. River bed and floodplain are never given a break by the mine to recover. The landslide soil and rock is different in composition from mine waste. No comparable impacts of landslides at other rivers are observed, like an aggradation of the Upper Ok Tedi in the course of 90 km, and a massive forest die back in the floodplain for another 100 km of the Lower Ok Tedi.
A helicopter flight down Ok Tedi
Massive aggradation of the Ok Tedi river bed at Tabubil
When the Ok Tedi enters the lowlands, it descends more smoothly and slower through its wide floodplain. Here the smaller grains of mine waste precipitate in such quantities, that the river bed is filled to the rim. The water floods the plain completely anytime the discharge is a bit higher than normal. Sand walls trap the water in ponds and oxbows, that it cannot retreat after a flood. Though vegetation is used to temporary inundation, it cannot stand that much. The rainforest has died in the plain on an area exceeding 500 km2 today. The Peer Review Group expressed concern, that ongoing impact may increase the dieback area to more than 2000 km2. Natural sediments were welcome to the gardeners along the river as a fertilizer. Because of the physical impact and unsuitable composition of mine waste, gardening along the dieback area has become impossible.
Ok Tedi and dieback area at Bige
The Fly River near Kiunga, upstream its junction with Ok Tedi. The river and rainforest are visibly intact. See it in the movie.
Copper is not completely extracted by flotation, so 120 tons/day of copper flow down Ok Tedi. Chemically, copper is tightly bound as insoluble sulphide on lime particles. If sulphides are exposed to air, they are converted to copperoxides, and sulfuric acid is set free. OTML says, one should not worry about that, because copperoxide is still insoluble in water, and lime, the prevalent rock from the pit, will neutralize the acid. This sounds plausible, if the tailings were disposed, e.g. on the Bige dredge site. In the river system, however, many biological processes take place, that may lead to mobilisation of copper and make it available to organisms. Some are very sensitive to copper, e.g. snails and prawns. Even undissolved copperoxide has a massive effect on mollusks: sea vessels are painted with copperoxide as a substitute for organic tin compounds, to prevent fouling. The effects of an annual load of 30,000 tons of a toxic metal cannot be covered by the present knowledge, and be predicted as not dangerous.
Hettler concludes from his investigations of sediments in the Middle Fly River area (1992 - 1995, PhD Thesis, sponsored by UNEP):
The areas of the innundation plain (of the Middle Fly)... play a central role for reproduction and feeding of fish. This part of the river ecosystem is most sensitive for changes of the ecological situation, caused by the mining project.
... it may last for centuries, till the copper enriched layer will be covered by an uncontaminated layer of sediment.
Original issue April 2001
Ok Tedi Environment - Rehabilitation?
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