Satellite imagery has prompted the BHP Billiton and Vale-owned Samarco to claim that the volume of waste material released into the Rio Doce river system when its tailings dam in Brazil’s Minas Gerais state collapsed is less than first thought.
Initial reports after the devastating November collapse put the volume of tailings (a non-toxic mix of water, silica, fine iron ore and manganese) at more than 50 million cubic metres. That has now been downgraded to about 32 million cubic metres.
The lower figure nevertheless represents one of the biggest ever tailings dam failures. It was also one of the most deadly, with 17 people killed and two still listed as missing.
The reach of the torrent of material that hit the valley floor and all but wiped out the nearby town of Bento Rodrigues has also been scaled back.
While the turbid red stain made its way to the Atlantic more than 600km down the river system, Samarco estimates 85 per cent of the material either pulled up, or was contained, within an 85km downstream stretch.
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