Soon after a failed coal-ash pond at a Tennessee Valley Authority powerplant in 2008 spewed waste onto 300 surrounding acres, Stantec Inc. senior engineer Alan Rauch was on a plane to Tennessee. Eventually, he took the lead to design a unique slurry wall around the failed dike, which saved TVA more than $473 million. His innovation may become a fix for utilities nationwide.
After running thousands of computer models on possible solutions, Rauch and his engineering team designed an 80-ft-deep segmented slurry wall, including perpendicular support walls, that will withstand 200,000 lb per linear ft of lateral load when project work finishes in 2014. "The really hard part in this closure is that we had to make sure the landfill could withstand an earthquake," says Rauch, noting the lakeside site's weak foundation and the risk that millions of cubic yards of ash set to be stored would liquefy. The liquefaction prediction expert is optimistic. "This technology can be used elsewhere," he says.