Brazilian regulators plan to tighten rules on dams used in the mining industry after a breach last year caused the nation's worst environmental disaster but the changes, while opposed by struggling companies, look unlikely to improve safety.
Environmental authorities say they will demand an increase in the number and focus of audits for hundreds of dams holding mining waste, known as tailings.
They also want to limit the size of dams and how often their walls can be raised to store more waste.
But engineers, prosecutors and tailings dam experts interviewed by Reuters say the changes will do little to prevent another tragedy if Brazil's chronically under-resourced regulators are not themselves improved.
When the Fundao dam burst in November at the Samarco mine, owned by BHP Billiton and Vale SA, enough mud to fill 12,000 Olympic swimming pools flattened an entire village, killed 19 people and left hundreds homeless.
The sludge flooded the Rio Doce river, choking fish and spitting them lifeless to the surface.
"Fundao is the Chernobyl of the mining industry. There is a before and there is an after," said Geraldo Abreu, head of licensing at the Semad environmental agency for the state of Minas Gerais where the spill occurred.
Abreu and the task force he joined to revise state and national rules for the industry in the wake of the disaster, is focusing on dams built the same way as Fundao, a design known as upstream.
It costs about half the price of other dams but is regarded as having a greater risk of failure because its walls are built on a foundation of mining waste rather than external material or solid ground. It is also the most common, holding back waste at mines across the world.
"We now understand that this type of dam needs to be treated carefully," Abreu said.
It is still not known exactly why Fundao failed, but Abreu says it was probably the result of a loss of stability in the tailings foundation, a process known as liquefaction.
This is usually caused by earthquakes but can result from other factors such as rapidly raising the dam's walls, which in an upstream design are built inwards on top of more dried tailings.
Under new rules to take effect this month or next, Abreu said miners will have to pay for an extra annual audit to check for liquefaction.
Licensing will also set a height limit on the dams and require companies to specify from the outset how much waste the dam will hold and set a date for closure. Existing dams and mines that do not comply could be forced to close.
Abreu said he initially backed an outright ban on upstream dams but others on the task force persuaded him against it, saying it would be an over-reaction.
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