Tennessee environmental regulators Monday slapped TVA with an $11.5 million penalty for its "catastrophic coal ash release" 18 months ago at the Kingston Fossil Plant.

The fine is the largest ever levied by state environmental regulators, and federal penalties also are possible, Tennessee Department of Environment and Conservation spokeswoman Tisha Calabrese-Benton said.

"These are appropriate penalties in response to an unprecedented event," TDEC Commissioner Jim Fyke said in a prepared statement.

The state's order says the Tennessee Valley Authority violated the Tennessee Water Quality Control Act and the Tennessee Solid Waste Disposal Act. Officials said TVA could additionally be fined for future natural resource damage.

For now, TVA must pay TDEC $2.5 million of the penalty by July 15, and at least $2 million in supplemental environmental projects to benefit the environment must be proposed by TVA and approved by TDEC by Dec. 31. If acceptable projects equaling at least $2 million are not proposed by Dec. 31, TVA must pay any remaining balance.

In addition, TVA must pay TDEC:

* Another $2 million by July 15, 2011.

* And still another $2 million by July 15, 2012.

Anda Ray, TVA senior vice president, environment and technology, said the federal utility has received Commissioner James Fyke's order and will comply with it, "as we remain fully committed to a complete cleanup of the Kingston ash spill."

A failed earthen landfill wall on the 50-year-old wet ash dump broke on Dec. 22, 2008. In the dark of night, a 5.4-million-cubic-yard wall of oozing ash - 1.2 million gallons - filled river sloughs, shoved onto residential farmland and into the Emory River's main channel. The spilled ash covered 300 acres and pushed one house across a road.

In the year and a half since, TVA has bought more than 100 properties touched or devalued by the toxics-laden ash spill.

Randy Ellis, a Roane County resident and member of two committees that worked with TVA and the U.S. Environmental Protection Agency to plan cleanup efforts, said he was glad to see the penalty but didn't think it was high enough.

"The $11.5 million fine by TDEC is a slap on the wrist considering the size and scope of the TVA ash disaster," he said. "But I am glad TVA was treated the same as any private company would have been treated in a situation like this."

He said the spill affected Roane County in a major way, and grants or environmental programs could help.

"I want to see that money find its way back to Roane County," he said.

Ms. Calabrese-Benton said TVA already has reimbursed the state $3 million in separate regulatory oversight costs as required by a January 2009 emergency commissioner's order. TVA must continue to pay these oversight costs over and above the $11.5 million total assessment, she said.

Ms. Ray said ash recovery work has progressed around the clock for more than 17 months and nearly three-fifths of the spilled ash has been recovered. It is being shipped to a disposal site approved by both state and federal authorities, she said.

"We are committed to make things right for the people of Roane County, and that will remain our priority until the job is done," she said.

EPA spokeswoman Davina Marraccini said EPA and TVA signed a consent agreement that says TVA will pay for all of the cleanup as well as EPA's oversight.

"If they violate any terms of the order we could at that point assess stipulated penalties against them," she said.

The cleanup has been estimated to cost $1.2 billion, and to date TVA has been estimated to have spent $500 miliion, she said.