The Tennessee Valley Authority's inspector general says a company overbilled the federal utility for work to clean up a 2008 ash spill at the Kingston Fossil Plant.
The inspector general's office audited costs billed to TVA by AMEC Environment and Infrastructure Inc., based in London, England.
It says the company overbilled TVA by nearly $2.2 million.
A summary of the report says AMEC loaded coal ash onto rail cars or trucks for off-site disposal under terms of a contract with TVA.
The audit looked at $19.3 million in costs billed to TVA from June 2, 2009, through Jan. 13, 2011.
TVA spokesman Duncan Mansfield said Monday that TVA is evaluating the findings and its response. AMEC said it takes its responsibilities seriously in working on public projects and disagrees with the audit's findings.