The cracking wall of an industrial plant reservoir could collapse at any moment and send a new wave of caustic red sludge into towns devastated by a deluge this week, Hungary's prime minister said Saturday.
A crack in the concrete wall widened by 2.76 inches (7 centimeters) overnight, Prime Minister Viktor Orban told reporters gathered at a fire station near the alumina plant that dumped up to 184 million gallons (700,000 cubic meters) of highly polluted water and mud onto three villages in about an hour Monday, burning people and animals. At least seven people were killed and hundreds injured.
Orban did not say how wide the crack had been, but he described collapse as imminent.
"Probably today, the wall could come down. I cannot say that it will happen surely, but already the risk is there," he said. "Cracks have appeared on the northern wall of the reservoir, which makes it very likely that the whole wall will collapse."
Red sludge is a byproduct of the refining of bauxite into alumina, the basic material for manufacturing aluminum. Treated sludge is often stored in ponds where the water eventually evaporates, leaving behind a largely safe red clay. Industry experts say the sludge in Hungary appears to have been insufficiently treated, if at all, meaning it remained highly caustic.
Most of what spilled Monday when the northeast corner of the reservoir collapsed was water, leaving behind slower-moving mud that has been kept in place by the remaining walls and barriers hastily erected in front of the ruptured section.
Orban said officials have started to build dams to the north, in the direction of lower-lying populated areas, to slow the mud in case of a second rupture.
The neighboring town of Kolontar, which was hit hardest in Monday's spill, has been evacuated. Officials believe they will have time to evacuate the next town of Devecser, 2.5 miles (4 kilometers) further north.
The prime minister said experts had estimated that an estimated 500,000 cubic meters of red sludge could escape from the reservoir if the wall collapsed, but said exact figures were hard to calculate.
"We have no exact information about the nature of the material because a catastrophe like this has never happened before anywhere in the world," Orban said. "We have only assumptions about how far and with how much force the material can come out of the storage container."
The reservoir, one of several at the Ajkai Timfoldgyar plant is about 650 yards (meters) long and 500 yards at its widest point. It's formed by walls at least 50 yards high that look like flat-topped hills, tapering from roughly 65 yards at their base to 45 yards at their tops, which are covered in vegetation and trees.
Zoltan Bakonyi, the CEO of MAL Rt., the Hungarian Aluminum Production and Trade Company that owns the plant told Hungarian news website Index.hu that the the walls are "medium-hard concrete." Authorities have not speculated about why they are cracking.
According to MAL, at least 95 percent of the sludge is still in the reservoir.
In Devecser, where the main street was deserted and an alcohol ban was in effect, Maria Gyori was having difficulties coming to grip with the evacuation plans.
"My husband and I want to stay until the very last moment and even then I'm not sure we'll leave," said the 79-year-old homemaker. "If another wave comes, I was thinking of standing on top of the kitchen table. Maybe the sludge won't go that high"
Gyori said she was exhausted and had been called by her son's family to join them at their home in Lake Balaton, 55 kilometers east of Devecser.
"I'm so tired and nervous, my mind isn't clicking like it usually does," said Gyori, a lifetime Devecser resident. "Of course I'm scared but abandoning our home will happen only as a final resort."
The red sludge devastated creeks and rivers near the spill site and entered the Danube River on Thursday, moving downstream toward Croatia, Serbia and Romania. Monitors were taking samples every few hours to measure damage from the spill but the volume of water in the Danube appeared to be blunting the red sludge's immediate impact.
The concentration of toxic heavy metals where the spill entered the Danube has dropped to the level allowed in drinking water, authorities said, easing fears that Europe's second-longest river would be significantly polluted.
Test results released by Hungary's disaster agency show the pH level of the water where the slurry entered the Danube was under 9 — well below the 13.5 measured earlier in local waterways near the site of the catastrophe. That is diluted enough to prevent any biological damage, Interior Minister Sandor Pinter said.
Despite the apparent good news, the risk of pervasive and lasting environmental damage remained at the site of the spill, with Greenpeace presenting laboratory tests that it said showed high concentrations of heavy metals in the sludge.
MAL Rt. has rejected criticism it should have taken more precautions at the reservoir.
Hungarian police have confiscated documents from the company, and the National Investigation Office was looking into whether on-the-job carelessness was a factor in the disaster.
Authorities began questioning people in the case and were looking for witnesses who could provide information about the reservoir's operations and maintenance work.
Orban said that the incident could have been avoided and that "there was no information diminishing the responsibility" of human error as a causing factor.
"Hungary has never experienced any tragedy like that and we are all astonished," Orban said. "Human errors and mistakes must exist ... and the (legal) consequences will be very serious. Someone has to answer for this."
He said a request from the company to allow production to begin again would not be granted at least until a government Cabinet meeting on Monday.
"We still have to gather a lot of information before we can decide whether to allow ... the plant to continue its operations," Orban said at Saturday's news conference in Ajka.
There are red sludge storage sites at several other locations in western Hungary, holding at least 30 million cubic meters (1 billion cubic feet) of the material.
Gorondi reported from Ajka.