(Source: The Knoxville News-Sentinel)
By Scott Barker, The Knoxville News-Sentinel, Tenn.
Jun. 25--KNOXVILLE -- A combination of factors, including a previously undetected layer of unstable ash sludge, led to the failure of the Kingston Fossil Plant fly-ash pond Dec. 22, an engineer contracted by the Tennessee Valley Authority said this morning.
The sludge layer, referred to as "slimes" by engineer Bill Walton of AECOM, consisted of ash, water and sediments underneath the ash pond. The unstable layer -- Walton compared its consistency to yogurt -- went undetected for decades by TVA engineers conducting stability analyses on the pond, he said.
Other factors included the looseness of the ash, the steepness of the retaining walls and the pressure exerted by the stacked ash, Walton said during a briefing at TVA headquarters.
"These four factors were leading to this problem," Walton said. "It's almost a perfect storm."
Walton's team discounted heavy rains in December and seismic activity as factors. Walton said the breach initially occurred at the northwest corner of the ash pond and took less than an hour to occur.
The analysis cost TVA nearly $3 million, utility spokesman John Moulton said, and comes six months after the disaster about 40 miles west of Knoxville.
A panel of federal and state regulatory experts will be reviewing it. So will lawyers suing TVA on behalf of hundreds of residents.
More than 5 million cubic yards of coal ash breached an earthen dike at Kingston, sending a wave of toxic-laden ash and sludge into the Emory River and 26 lakeside homes, covering 300 acres. TVA expects the cleanup could cost as much as $1 billion.
-----
To see more of The Knoxville News-Sentinel or to subscribe to the newspaper, go to http://www.knoxnews.com.
Copyright (c) 2009, The Knoxville News-Sentinel, Tenn.
Distributed by McClatchy-Tribune Information Services.
For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA.
NYSE:ACM,
A service of YellowBrix, Inc.
