"todayonline: The cracking wall of an industrial plant reservoir appears on the verge of collapse, and engineers have been working to blunt a possible second wave of the caustic red sludge that has already deluged several towns in western Hungary and killed seven. Engineers fear a second wave could be even more toxic than the first because the sludge remaining in the reservoir was more concentrated. Prime Minister Viktor Orban said the northern wall of MAL Rt.'s storage pool is showing numerous cracks and seems ready to fail completely. Engineers were building retaining walls around the previous breach in 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. "