There was supposed to be a three-month window. It didn’t materialize. Instead, the old water filtration plant in Hendersonville, Tennessee, closed at 10:09 a.m., and at the same time, a new one started up 1,000 feet away. It was Aug. 26, during the peak demand season. “Needless to say it was an interesting day,” says John Wunner, water treatment superintendent in Hendersonville, about 18 miles from downtown Nashville.