The Tennessee Valley Authority said today it may have to spend up to $975 million to clean up the ash spill at its Kingston Fossil Plant — $150 million more than what the utility estimated a month ago.

In a securities filing today, TVA said it has spent $77 million already on its initial cleanup and ash removal efforts in Kingston. But the agency now says the cleanup ultimately will take years and is likely to cost between $675 million and $975 million. Previously, TVA had estimated the maximum cleanup cost at $825 million.

Most of the extra cost included in today’s estimate is due to higher-than-expected expenses to transport and store the ash once it is removed from the Emory River and adjacent property. More than 5.4 million cubic yards of ash spilled out of a storage pond on Dec. 23. The ruptured pond had stored ash residue from the Kingston coal plant for more than a half century.

“TVA currently believes the recovery process will take several years,” agency officials said in a filing with the U.S. Securities and Exchange Commission. “The revised estimate (for the higher ash cleanup costs) reflects an increase in the number of cubic yards of ash that will need to be transported offsite versus what could be stored on site.”

TVA still is searching for a permanent storage site for the spilled ash being removed from the river.

In the three-month period ended March 31, TVA reported net income of $133 million on revenues of more than $2.9 billion. A year ago, TVA earned $135 million on revenues of $2.5 billion.

For complete details, see tomorrow’s Chattanooga Times Free Press.