DEVECSER, Hungary — The cracking wall of an industrial plant reservoir appeared on the verge of collapse late Saturday, and engineers were working to blunt a possible second wave of the caustic red sludge that has already deluged several towns in western Hungary and killed seven.
Residents of one nearby town were evacuated, others were ordered to be ready to evacuate, and everyone was bracing for a new onslaught of toxic material. Engineers feared a second wave could be even more toxic than the first because the sludge remaining in the reservoir was more concentrated.
"If another wave comes, I was thinking of standing on top of the kitchen table," said Maria Gyori, a 79-year-old homemaker in the town of Devecser. Maybe the sludge won't go that high."
Prime Minister Viktor Orban said the northern wall of MAL Rt.'s storage pool, which released at least 700,000 cubic meters (184 million gallons) of caustic red sludge and water five days ago after one of its corners ruptured, was showing numerous cracks and seemed ready to fail completely.
"Because it may happen at any moment, but it's also possible that it won't happen ... there's only one thing we can do – we have to behave as if this could happen any minute," Orban told reporters in Budapest. "There's no technical equipment that could really stop this process and the only thing we can do is prepare ourselves to stop the damage it would cause."
Engineers were building retaining walls around the previous breach and the weakened wall of the reservoir just outside Kolontar, the town hardest hit by the sludge flood. Kolontar's nearly 800 residents were evacuated early Saturday as a preventive measure.
On Monday, the highly polluted water and mud flooded three villages in less than an hour, burning people and animals. At least seven people were killed and at least 120 were injured. Several of those who were hospitalized were in serious condition.
Orban said the latest dams, in the direction of lower-lying populated areas, were meant to slow the mud in case of a second rupture and give officials time to warn the population.
The roughly 6,000 residents of Devecser, 2.5 miles (4 kilometers) north of Kolontar – and that much further away from the reservoir – were told by police to pack a single bag and get ready to leave at a moment's notice.
The prime minister said experts had estimated that some 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 Saturday morning at a fire station in Ajka, a city where many Kolontar residents were taken. "We have only assumptions about how far and with how much force the material can come out of the storage container."
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 was water, leaving behind slower-moving mud that has been kept in place by its own mass, as well as the remaining walls and barriers hastily erected in front of the ruptured section.
The reservoir, one of several at the Ajkai Timfoldgyar plant, is about 650 yards (600 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 thick 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 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, the 79-year-old homemaker, was having difficulties coming to grip with the evacuation plans. She 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.
"My husband and I want to stay until the very last moment and even then I'm not sure we'll leave," said Gyori, a lifetime Devecser resident.
"I'm so tired and nervous, my mind isn't clicking like it usually does," she said. "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.
The BBC reported that in the Marcal River, one of the feeder streams to the Danube, "all life ... is said to have been extinguished." It said emergency crews were adding gypsum and other chemicals to try to reduce the toxicity in another feeder, the Raba River.
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 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.
Orban said special attention was being paid to block any new sludge spill from reaching the Duna, as the Danube is called in Hungary.
"We have taken the precautions and accumulated the materials needed to prevent the contamination from reaching the Danube," Orban said. He was referring to the retaining walls as well as chemicals that could be poured into waterways to neutralize the highly alkaline mixture.
Still, the risk of pervasive and lasting environmental damage remained at the site of the spill. Greenpeace presented laboratory tests 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 have begun questioning people in the case and looking for witnesses who can provide information about the reservoir's operations and maintenance work.
Orban said the incident could have been avoided and "there was no information diminishing the responsibility" of human error as a factor.
"Hungary has never experienced any tragedy like that and we are all astonished," Orban said. "Huge damage has occurred, we've lost lives, and the region's future livelihood has been lost. Someone must be to blame for this. The responsibility and the punishment ... must be commensurate with the damage caused and the costs of those damages."
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 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.