Just ahead of the start of the summer boating season and the Memorial Day weekend, the Tennessee Valley Authority on Wednesday celebrated the completion of its biggest and most expensive repair of one of its 29 hydroelectric dams to restore full hydro generation and lake levels at the Boone Reservoir in Northeast Tennessee.
After 2 million hours of work and $326 million of dam remediation expenses, TVA crews completed the construction of a seepage barrier beneath and around the Boone Dam on the South Fork Holston River. The repairs made over the past seven years will limit water leaks at one of the three hydro units at the 70-year-old dam.
Although the repairs were the costliest ever for a TVA hydroelectric facility and forced the shutdown for more than seven years of one of the three hydroelectric generating units at the Boone Dam, the project was ultimately done within budget and on time, TVA officials said.
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"At the onset of this project, we made a commitment that we would complete this effort safely within seven years and we would do it right the first time with a high-quality repair," TVA Chief Operating Officer Don Moul said in prepared remarks during a ceremony Wednesday afternoon at TVA's Boone Dam. "Boone Lake is a local treasure, and I want to thank everyone for their patience as we completed the important dam safety work."
In October 2014, TVA discovered a sinkhole near the base of the embankment at Boone Dam, and water and sediment was found seeping into the riverbank below the dam. While sinkholes are not uncommon in East Tennessee, the location of the sinkhole and the muddy discharge were indications of potential safety problems at the dam. Such internal erosion is one of the leading causes of dam failures around the globe, TVA spokeswoman Mary Ellen Miller said in a phone interview.
To correct the problem, TVA constructed a composite seepage barrier in several phases, including an underground cutoff wall. Following completion of the underground work, TVA restored the crest of the dam to its previous elevation and constructed a floodwall. Paving and fencing, along with site restoration, round out the project.
Moul said the project is a major geotechnical engineering feat.
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"TVA has delivered on its promise to the Tri-Cities region," he said in a statement Wednesday. "The recreation area provides the community with opportunities for summer fun, and the improvements we made will enhance the experience for our neighbors."
TVA expects to resume power generation at its Unit 1 hydroelectric generator in early June. Lake levels on Boone Lake, which had to be lowered during most of the past seven years while the dam repairs and seepage wall were completed, returned to summertime pool levels of 1,382 feet earlier this month ahead of the usual June 1 target date, Miller said.
"The Boone Dam project exemplifies all three aspects of TVA's mission of service," TVA President Jeff Lyash said in a statement about the completion of the dam repairs. "Environmental stewardship by providing a beautiful recreational area for families to picnic, swim and relax this summer; economic development with a lake that helps communities in the Tri-Cities region prosper from fishing tournaments to boating activities and much more; and electricity that is clean, reliable and generated right here at the Boone Dam hydropower facility."
After several years of lower lake levels on the Boone reservoir during the dam repairs from 2015-20, TVA was able to bring the lake up to normal summertime levels for most of last year and again this month for the summer season ahead. That is helping give a boost tourism in upper Northeast Tennessee, according to Frank Lett, the senior associate executive director for Visit Kingsport.
"People are excited that the lake is back to full pool again, and we expect that will help to boost some of the marinas and boating activity on the lake this summer," Lett said in a telephone interview Wednesday. "Gas prices will be a bit of a challenge this year, but we're still expecting a better tourism year."
Contact Dave Flessner at dflessner@timesfreepress.com or at 423-757-6340. Follow him on Twitter at @dflessner1.
About Boone Dam
History: Construction of the dam began in 1950 and was completed in 1952.Location: Kingsport, Tenn., on the South Fork Holston River.Size: The dam is 160 feet high and stretches 1,697 feet across the river.Lake storage: The reservoir has a flood-storage capacity of 75,800 acre-feet. In a year with normal rainfall, the water level in Boone Reservoir varies about 25 feet from summer to winter to provide seasonal flood storage.Power generation: Boone Dam has three generating units with a summer net dependable capacity of 114 megawatts.Name: The dam and reservoir are named after Daniel Boone, an 18th-century American pioneer and frontiersman who blazed the Wilderness Road through the Cumberland Gap and into Kentucky.Source: Tennessee Valley Authority