IDI and the North Sumatra Advocacy and Legal Aid Association (Bakumsu), a local NGO, helped residents file their CAO complaint in October.

The dead and displaced: Indonesia counts cost of wave of natural disasters

Building a tailings dam “in the middle of one of the riskiest places in the world for earthquakes” means that villagers living downstream from the mine site “will be forever living in fear of dam collapse and water contamination,” said David Pred, IDI’s executive director. “Dam collapses in other areas of the world – even without such high earthquake risk – have destroyed villages, killed hundreds of people and poisoned the environment for generations.”

He said in a recent press release that the CAO’s acceptance of the complaint was “an important step in avoiding a similar disaster in North Sumatra”, though in its internal letter, the CAO said its decision “does not imply any judgment”.

Work on the zinc mine has already begun. Last June, an explosives storage facility was built just 50 metres away from a small settlement called Sipat, according to lawyers from Bakumsu and the Mining Advocacy Network (JATAM) that provides local communities with legal aid.

Merah Johansyah from JATAM said they suspected this facility, which has the capacity to hold some 5,000kg of dynamite and 100 tonnes of ammonium nitrate, was built without a valid environmental impact assessment or disaster risk analysis being carried out.

In 2005, a blast at an explosives factory in Zambia owned by an African subsidiary of China Nonferrous Metal Mining Group killed at least 50 workers. The same subsidiary was among seven mine investors investigated by the Zambian government in 2016 following accusations they had polluted the country’s drinking water.

In May, Indonesia’s parliament passed a controversial new mining law that allows operators to extend permits and seek expansion of their operations beyond current legal limits.

Sugianto Hasugian, a representative of the complainants, said in a statement released through local NGOs working on the case that residents needed more detailed information about the planned mine and an independent expert who could help them understand the technical aspects “because no one can be sure if … [it will] cause a big risk”.

The accidental release of “millions of tonnes of toxic waste in our fertile area” would be devastating for local agriculture, said fruit farmer Rainim Purba of Pandiangan village, who worried that her children and grandchildren would be left with nothing to inherit. “This can ruin our lives,” she said.

Andreas Harsono, a researcher with Human Rights Watch Indonesia, which was not involved in filing the CAO complaint, said a lack of consultation or any official response was common in the country’s land disputes.

“Conflicts related to land are pervasive and have frequently been linked to oil palm plantations and mining companies,” he said, adding that opposing such developments are often arrested or jailed “under various laws including anti-communist provisions, public order laws, and criminal defamation”.

In a written statement, the IFC said it supports the CAO’s work, “is committed to environmental and social sustainability” and welcomes “a productive dialogue” to address issues associated with its investments.

Dairi Prima Mineral, which did not respond to emailed requests for comment, says on its website that it “commits to the highest standards of environmental care, occupational health and safety and corporate governance”.

NFC, Bumi Resources Minerals and Indonesia’s environment ministry did not respond to requests for comment.