Duke Energy said Friday that it was diverting the flow of coal ash away from the Dan River, but the company could not yet declare the huge spill fully contained nearly a week after it was discovered. Meghan Musgrave, a company spokeswoman, said that engineers at the Dan River Steam Station had designed a containment system that is capturing nearly all of the toxic runoff and pumping it back into a storage basin. Duke says up to 82,000 tons of coal ash mixed with 27 million gallons of contaminated water have escaped since a drainage pipe collapsed Sunday under a 27-acre waste pond. Officials 20 miles downstream in Danville, Va., said they were successfully filtering arsenic, lead and other toxins from drinking water.