TVA finishes massive ash spill retaining wallMar 4 - McClatchy-Tribune Regional News - The Knoxville News-Sentinel, Tenn.
It's the largest wall of its type -- almost 64,000 linear feet -- and it was finished nearly a month ahead of schedule, according to TVA officials. The utility giant on Monday observed what officials called a "significant milestone" in its ongoing cleanup of the disastrous ash spill at its Kingston Fossil Plant -- the completion of the retaining wall to store the remaining ash that burst from a holding cell in December 2008. The work wrapped up late last month. More than 200,000 tons of cement and other materials were used to build the underground wall, which is embedded as deeply as 70 feet into bedrock. It's built to withstand a magnitude 6.0 earthquake. Construction of the wall, equal to 12 miles in length, began in the summer of 2011 and involved the use of special long-reach excavators to dig 4-foot wide trenches ranging from 40 to 70 feet deep, according to TVA. "Construction of the wall is an impressive engineering achievement," said Craig Zeller, on-site administrator for the U.S. Environmental Protection Agency. The remaining cleanup project is now concentrating on the completion of the cap that will go over the remaining ash from the 5.4 million cubic yard spill. The wall encloses the 240-acre containment cell. According to TVA, the project remains under budget and on schedule, with completion scheduled by the end of the year. The ash spill, expected to cost more than $1 billion to clean up, prompted a huge shift in TVA's game plan for storing the residual, toxic ash from its coal-fired plants. Wet storage of ash is being phased out, and dry storage systems are being installed at TVA's coal-burning power plants at an estimated cost of $1.5 billion to $2 billion. That conversion should be finished by the end of 2022. |