BHP-Vale Dam in Breach Was Upgraded With First Rubber Top

  • Concrete spillway raised one meter at Santarem dam in 2014
  • UK's Dyrhoff has been in touch with Samarco to offer help

One of the two dams that burst at an iron-ore mine in southeast Brazil Thursday had been upgraded with an inflatable rubber top that was the first of its kind to be used in Brazil, according to its designer, Dyrhoff Ltd.

Samarco Mineracao SA, a joint venture between BHP Billiton Ltd. and Vale SA, commissioned Dyrhoff to design and supply the rubber dam in 2014, according to Dyrhoff’s director, Don Mason. Mason said he doesn’t know which of the two failed dams, Santarem or Fundao, burst first and has no information yet about the cause.

The ruptured structures, which triggered mudslides that buried dozens of homes, were deemed “totally safe” by authorities in July, according to Samarco. The inflatable rubber top is meant to provide an advantage in times of high water flow because it can deflate, reducing the pressure on the underlying concrete structure, Mason said in a telephone interview from Kent, in the U.K., on Friday.

“But having said that, it’s up to the dam safety people, or the engineers, to calculate the impact of any additional load that would be placed on the structure by raising the water level by one meter,” he said.

“We designed and we supplied an inflatable rubber dam which was one meter high and 30 meters wide, and that was installed on the spillway of the Santarem dam,” Mason said. “There was a concrete spillway, and it raised the level of the spillway by one meter.”

Safety Laws

Samarco also performs its own inspections according to federal safety laws, it said Friday in a statement posted on its Facebook account.

Before the rubber dam was installed on the pre-existing concrete dam, “about 70 percent of the reservoir capacity had been used up by tailings disposal, thus reducing the availability of water to be abstracted,” according to a December 22, 2014 post on the Dyrhoff website.

BHP’s Chief Executive Officer Andrew Mackenzie told reporters in Melbourne that a full investigation would be required to establish the cause of the incident in Brazil, and the company would fully cooperate with local authorities. In an e-mail statement on Friday, Vale said it has offered support and assistance to local authorities.

Rescue Workers

Samraco said it was working with police, firefighters and other rescue workers to attend to the injured and homeless in and around the traditional mining town of Mariana in the state of Minas Gerais. It couldn’t confirm the number of victims and missing or the cause of the accident. A local hospital confirmed one death while a mining union reported 15 to 16 fatalities and 45 people missing.

The wall of mud hit Bento Rodrigues, a village with about 600 inhabitants, and the number of people affected in the area could rise to 2,000, the Globo news website reported, citing estimates from the prefecture where the mine is located. The mud flow is 8 kilometers (five miles) long and 2.5 meters (8 feet) deep, Globo said, citing military police.

The waste material, known in the industry as tailings, is mostly silica from iron-ore processing and doesn’t contain chemicals that are harmful to health, Samarco said.

In an e-mailed statement Friday, Vale expressed solidarity with those affected and said it has offered support and assistance to local authorities.

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