KNOXVILLE, Tenn. (AP)  The Tennessee Valley Authority has spent more than $20 million buying up 71 properties tainted by a major coal-ash spill and is negotiating to buy more. But the public utility, the nation’s largest, has also turned down 160 property owners hoping to sell out.

“We are trying to balance between doing the right thing by the people that were impacted by this,” said Peyton T. Hairston Jr., a senior vice president at the Tennessee Valley Authority.

Mr. Hairston said the utility was also “keeping in mind that this is ratepayer money.”

The agency has received more than 200 requests from property owners wanting to sell tracts that they felt were damaged or devalued by the release in December of 5.4 million cubic yards of coal ash after a retaining wall breach at Kingston Fossil Plant, about 40 miles west of here.

“As we work through this process,” Mr. Hairston said, “we have been able to determine that some people are just outside the area that we feel has been impacted.”