Duke Energy has withdrawn a request for state permission to use an additive at its coal-fired power plants that caused problems two years ago with Charlotte's drinking water. Environmental groups had sued, and celebrated the move. Duke said its decision was unrelated to the challenge.
Duke told state environmental regulators in a letter last week it will no longer use a chemical called calcium bromide to remove mercury from coal before it's burned. The idea was to keep mercury out of the air, said Duke spokeswoman Erin Culbert.
"We thought that might be one of the options that we needed for mercury removal, to meet air standards. But since then, we have had really good operational experience and we know that we can meet those standards consistently without the use of bromide," Culbert said.
Duke began using the chemical at plants on Lake Wylie and Lake Norman four years ago. Bromide in the leftover coal ash found its way into the lakes, and into Charlotte's water supply.
Bromide by itself isn't a problem. But when it combines with chlorine used to treat drinking water, it creates cancer-causing compounds called trihalomethanes.
Charlotte Water found those compounds two summers ago. Duke voluntarily changed its process and the system returned to normal.
But environmentalists worried Duke could start using the chemical again, said Catawba Riverkeeper Sam Perkins.
"Duke said they would stop using bromides, yet at the exact same time they were starting the re-permitting process for their power plants, and they continued, with these permits, asking for the ability discharge more bromides," Perkins said.
So this spring, the Southern Environmental Law Center challenged the permits on behalf of the Riverkeeper and another group, Clean Air Carolina.
After Duke's announcement, environmental groups cheered. But Culbert said there’s no connection between Duke’s decision to withdraw the permit language and the legal challenge.
"It was a decision that we made because we understood that downstream water users were sensitive to the issue and we wanted to reassure them that that was not an option for us," she said.
The Southern Environmental Law Center said despite Duke's move, other threats remain from coal ash ponds near waterways around the state.