VietNamNet Bridge - The tailings dam break at Corrego do Feijao in Brazil in January has raised the fear that a similar disaster may occur at the red mud reservoirs in the Central Highlands of Vietnam.

A report from Greenpeace about the accident, which killed more than 120 people, showed that mercury and arsenic content in the red mud on the site was ‘surprisingly high’.

The accident has once again sparked worry about the safety of the red mud reservoirs at Nhan Co and Tan Rai bauxite mines, though Vinacomin, the investor of the projects, has reassured the public that the reservoirs are safe.

An analyst said Vale, the owner of Feljao mine in Brazil, is the second largest mining group in the world and the biggest iron exploiter and pellets processor. Feijao is an open cast mine.

“This means that incidents may occur even when the mining is carried out by a large corporation.”

Local newspapers reported that in 2018, due to the high rainfall, deep holes appeared next to the tailings dam at Nhan Co bauxite project in Dak Nong province, which may lead to subsidence and dam failure. This once occurred in Hungary in 2010

In Vietnam, an incident at the bauxite tailings reservoir occurred at Tan Rai mine in Lam Dong province on October 8, 2014.

The discharge from sorting workshops to iron containing reservoirs includes iron pieces w smaller than 1 mm, mud and water from sludge settling machines. If the waste water spills into ponds, lakes and fields, it will kill fish, microorganisms, rice and crops.

Scientists said there is a risk of alkaline leaking into underground and rainwater, which may lead to the spillover at the Tan Rai and Nhan Co red mud reservoirs.

The waterproofing panels used to line the bottom of the reservoirs are mostly geotechnical membranes.

Experts advise against using this membrane in an alkaline environment and for a long time. Studies have found that this membrane is only suitable for waterproofing chemicals for 50 to 100 years.

HDPE film has very good resistance against chemicals, but it will crack in the environmental pressure and heat. The Tan Rai project uses this type of membrane.

Scientists have warned of the possible pollution to the water underground system.

Designers and contractors of reservoirs in Vietnam all say they strictly follow technical regulations. 

However, accidents still occur. The accident at Na Lung mine in Cao Bang in 2010 buried hectares of rice fields and houses.

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Thanh Lich