Background

Dairi Prima Mineral was planning to build an underground mine to commercially extract zinc, lead and silver ore in a mountainous area of North Sumatra, Indonesia. Zinc would be the focus of the mine.

Dairi Prima Mineral claimed that most of the waste from the mine will be mixed with cement and injected back underground. However, millions of cubic meters of remaining toxic waste would be stored in a tailings dam located 2 kilometers from the mine. Initially DPM have said a 25-meter high dam wall is required for mining period of 8 years. There was is considerable uncertainty about how much tailings could be put back into the underground cavity (mixed with cement) and how much will be left to be stored in a tailings dam. Technical experts said DPM is seriously under-stating just how much tailings will need to be stored in a dam.

The big issue was, if not properly located, constructed and maintained, tailings dams could fail, releasing toxic waste into the surrounding environment. Even those companies that claim to implement more modern security measures have a high failure rate (2 to 5 per year worldwide). One major tailings dam collapse in Brazil was captured on camera (https://www.youtube.com/watch?v=NK6EDKOys5E). In that Brazilian disaster 272 people were killed and hundreds of kilometers of river system were poisoned. This was the sort of disaster the proposed DPM tailings dam could create.

An expert report commissioned by a consortium of NGOs on the seismic risk posed by Prima Mineral's Dairi project concluded that “The Dairi Mine is located in one of the highest risk areas in the world,” located near the Sumatra subduction Megathrust which in 2004 and 2005 produced earthquakes respectively power 9 and 8+ respectively. The mine site is also only 15 kilometers from the Great Sumatran Fault which produces long-term or repeated earthquakes, known to be capable of damaging civil structures such as tailings dams (especially “wet tailings”, such as will be generated in Dairi). These factors, combined with the region's torrential annual rainfall, led the study authors to estimate that “within decades of deposit 'closure',” a sudden tailings dam failure caused by an earthquake would send “a wave of liquid mud over the region” downstream to the north.”

The social and environmental impacts of a collapse would be catastrophic. Dam collapses in other regions of the world – even without a high risk of earthquakes – have destroyed countless villages, killed hundreds of people, and poisoned the environment for generations. There are at least around 11 villages around or downstream of the proposed Dairi Prima Mineral mine. Study by Dr. Richard Meehan reviewed the 2022 DPM AMDAL Addendum concluded that not only were the risks not adequately weighed, the geological information on the location of the proposed tailings dam appeared to be being withheld – further increasing concerns about the DPM’s commitment to safety and environmental protection.

A study of the 2022 Dairi Prima Mineral AMDAL Addendum by technical expert Dr. Steve Emerman concluded that the Dairi Prima Mineral mine, if built in China, would violate new Chinese regulations created after the tailings dam disaster in Brazil. This practice is illegal in China because it can pose unacceptable risks to human life – yet Dairi Prima Mineral apparently intended to build its mine and tailings dam in Dairi - within 400m of a settlement, with churches and mosques where large numbers of people could congregate.

Lead-zinc mines such as those owned by Dairi Prima Mineral are some of the most environmentally problematic mines in the world. The mine will extract sulfide ore, which can form sulfuric acid when it reacts with water and oxygen. Acidic conditions can cause acidic mine drainage where heavy metals dissolve in the water and then spread throughout the water system. Technical expert Dr. Steve Emerman found that the 2022 EIA DPM Addendum did not account for these risks according to international standards. The risk of flooding was underestimated and there was no adequate provisions for containing toxins. He estimated that the tailings dam, if completed, would have overflowed, emptying untreated water into water supply streams 15% of the time.