The Tennessee Department of Environment and Conservation also released a statement saying there was no indication of risk unless the ash was ingested.

Image The area around the Kingston Fossil Plant in Harriman, Tenn., where 5.4 million cubic yards of coal ash spilled on Monday.

But residents like Deanna Copeland were thinking further into the future.

“Our concern is, what happens if this liquid dries out?” Ms. Copeland said. “There are huge health concerns. It’s going to get in our house. We’re going to breathe it in. It would be like walking through a dust bowl, and we don’t know what’s in the dust.”

A round-the-clock cleanup effort continued on Friday, much of it clearing roads and railway tracks that were blocked by the sludge. Several booms, or skimmers, were installed on nearby rivers to catch floating cenospheres, a valuable component of the ash used to make bowling balls and other manufactured goods. A weir, or underwater dam, that would keep settled ash from moving downstream was about one-fifth completed, T.V.A. officials said.

Some nearby residents said that the authority had done little to address their concerns.

“We’re terribly frustrated,” said Donald Smith, 58, a laboratory facilities manager who lives in the affected area. “It seems like T.V.A. is just throwing darts at the problem, and they don’t have a clue how to really fix it.

“It was nice that they came by to talk to us. They’re making an effort. But what upsets me is they didn’t have a plan in place. Why hadn’t anybody thought, ‘What happens if this thing bursts?’ ”

Residents said they were stunned by the new figure for the size of the spill.

“That’s scary to know that they can be off by that much,” said Angela Spurgeon, whose dock and yard are swamped with ash. “I don’t think it was intentional, but it upsets me to know that a number was given of what the pond could hold, and the number now is more than double.”

Authority officials offered little explanation for the discrepancy, saying the initial number was an estimate based on their information at the time.