River Pollution and Ecosystem Damage at Ok Tedi Mine, Papua New Guinea

Problems

• Severe Environmental Degradation from Mining Activities

   The Ok Tedi Mine has caused severe environmental damage since operations began in 1984. According to UNEP, the mine has discharged approximately 70 million tonnes of waste rock and tailings annually into the Ok Tedi River, with impacts extending more than 1,000 km down the Ok Tedi and Fly river system, raising riverbeds and causing widespread sedimentation, flooding, and forest damage. Since 2008, Ok Tedi Mining Limited has implemented mitigation measures including sulphide removal from tailings and sediment dredging at Bige, though treated tailings continue to enter the river system as the company studies a transition to a conventional tailings storage facility that could eventually eliminate riverine tailings discharge.

• Impact on Local Biodiversity

  Mine-derived sediment and changes to river habitat have caused major declines in fish abundance and species diversity in parts of the Ok Tedi and Fly River system. Long-term studies found reductions in fish biomass of roughly 65-96% at some affected sites relative to pre-mine levels, though many species have persisted in tributaries or elsewhere in the river system rather than becoming extinct. Because fishing is central to subsistence and livelihoods for many river communities, this decline in fish abundance has significantly affected traditional diets, food security, and ways of life. In a positive sign, Ok Tedi Mining Limited reported in December 2024 that it had rediscovered fish species in the Fly River that had not been recorded for roughly 40 years.

• Pollution Pathways and Water Quality Deterioration

  Mine waste has introduced large quantities of sediment and metals into the Ok Tedi-Fly River system. Copper is the most directly relevant pollutant given the mine's copper-gold operations, and Ok Tedi Mining Limited continues to monitor dissolved copper along roughly 1,000 km of the river system, reporting that concentrations have decreased over time due to lower ore grades, improved recovery, and sulphide removal. The environmental story is centered on surface water and floodplain contamination; there is no specific hydrogeological study establishing broad groundwater contamination from the mine. Claims of arsenic and mercury contamination, or of a resulting public-health crisis with elevated heavy metals in residents' blood, are not supported by credible, Ok Tedi-specific evidence and should be treated with caution absent a documented study.

• Socioeconomic Impacts on Indigenous Communities

  The environmental degradation caused by the Ok Tedi Mine has significantly affected the indigenous communities living along the Ok Tedi and Fly rivers. An assessment associated with the mine's compensation area estimates roughly 50,000 residents across around 120 villages affected by mine-derived waste, with declines in fish stocks and changes to agricultural land disrupting traditional livelihoods for many families. The mine has also generated substantial economic benefits alongside these environmental and social costs, producing a long history of compensation arrangements, benefit-sharing, and legal disputes. In 1994, landowners filed a lawsuit against BHP, the mine's then-majority owner, in Australia's Supreme Court of Victoria over environmental and livelihood damage; a settlement was reached in June 1996 that included a compensation package and commitments to reduce tailings-related environmental impact.

• Corporate Withdrawal and Changes in Mine Ownership

  Ok Tedi's environmental damage has a well-documented corporate and legal history. In February 2002, BHP Billiton withdrew entirely from the mine, transferring its 52% stake to the newly established PNG Sustainable Development Program (PNGSDP), which was created to direct future mine proceeds toward development projects for Papua New Guinea. In 2013, Papua New Guinea passed legislation restructuring ownership of the mine: it cancelled PNGSDP's shares and issued new ones to the state, bringing Ok Tedi under full government ownership. This history of changing ownership and legal accountability, alongside the 1994-1996 litigation and settlement with BHP, is central to understanding how the mine's environmental impacts have been addressed over time.