The cost of repairing the 65-year-old Boone Dam in Northeast Tennessee has risen by at least 50 percent from what the Tennessee Valley Authority estimated the fix would cost when the work began in 2015.
To shore up seepage problems in the TVA dam on the South Fork Holston River, TVA estimates it will now likely cost the utility $450 million and take another five years to complete. When work began, TVA estimated more than two years ago the Boone Dam repairs would cost between $200 million and $300 million and could be completed as soon as 2020.
TVA started investigating problems at the dam in October 2014 and launched construction of the composite seepage barrier in July 2015.
"As we got farther into the work there, we learned more about what is actually happening and that provided us the data to make a more robust estimate," TVA President Bill Johnson told analysts during a conference call last week. "As design and construction plans are finalized for this ongoing, multi-year project, the estimated costs and duration are being refined and we expect to invest in the range of $450 million to secure the Boone project completion in 2022."
The repair project is one of the most expensive ever at a TVA dam, but Johnson said the seepage problem at the Boone dam does not indicate any systemic or widespread problems across TVA's network of 49 dams on the Tennessee River and its tributaries.
"These dams were built in different times, on different geologies and with different construction methods," Johnson said. "Some are earthen, some are concrete and some are both. There is no systematic extent of condition here that would make us concerned about other dams."
Over the next five years, TVA expects to spend another $200 million on safety inspections and repairs on its dams across its seven-state service region.
"When you are looking at all of the 49 dams and their embankments, occasionally we will find these challenges," TVA spokesman Jim Hopson said. "These are all unique and all different, but we repair them as we find them. The cost of the Boone Dam repairs has gone up, but this is the first real estimate of what it would cost."
Johnson said TVA's ongoing dam inspection program has uncovered problems at a couple of other dams, including some being addressed at the 79-year-old Pickwick Dam in southwest Tennessee. But the costs of repairing the other dams will be significantly less, Johnson said.
Boone Dam Project Manager Sam Vinson said in a recent TVA report that a lot of progress has been made during the past year and a half of work. About 800 holes have been drilled and grouted in the earthen embankment and will provide important data for the remainder of the project and for the final design.
"Like similar aging facilities we have relied upon for decades for hydroelectric production and flood control, Boone is an important part of the infrastructure our country relies upon every day," the TVA CEO said in his quarterly earnings report last week. "These assets require regular maintenance and repairs to stay at peak performance and TVA is committed to maintaining the dams that have been entrusted to us."
Contact Dave Flessner at firstname.lastname@example.org or at 423-757-6340.