by Bill Mardis
Work continues below Wolf Creek Dam to extend a cutoff wall to protect the nearby switchyard area, and on the upstream side of the dam the work platform created for the rehabilitation project will be reduced in size.
The cutoff wall under construction is actually an extension of the cutoff wall installed during the 1970s when serious leaks developed in the dam during the late 1960s. Two large sinkholes developed in the switchyard area and muddy water was observed in the tailrace.
The condition of Wolf Creek Dam during the late 1960s, in the opinion of some, was more serious than in 2005 when the dam was declared in high risk of failure. Intensive grouting during the late 1960s slowed the seepage, and a concrete barrier wall, not long enough and not deep enough, was inserted in the earthen section of the dam during the 1970s.
The dam continued to leak, getting worse as years went by. A just-completed, $594 million rehabilitation of the dam is believed to be a permanent fix for the uncontrolled seepage problem.
Engineers with the U.S. Army Corps of Engineers’ Nashville District believe fluctuation of waters in the tailrace is a factor in undermining the switchyard area. That is the reason for extending the cutoff wall. Entirely underground, the to-be-constructed extension will be 180 feet long and 120 feet deep. It will be completed in late winter or early spring.
The cutoff wall extension will be constructed by drilling 50-inch overlapping holes, same as the barrier wall in the dam. “This extended cutoff wall near the switchyard has absolutely nothing to do with the lake,” emphasized Don B. Getty, manager of the Wolf Creek Dam Rehabilitation Project.
Getty said current work on the cutoff wall is near the powerhouse and is not affecting fishing immediately below the dam. Efforts by the Corps of Engineers earlier this year to ban fishing within 500 feet of Wolf Creek and other Corps-operated dams created a brouhaha that reached the halls of Congress. Eventually the U.S. House and Senate placed a two-year moratorium on the Corps’ plans to keep fishing boats in the tailwaters from getting close to the dam.
“That still doesn’t mean it’s not dangerous to get up close to the dam,” said Getty. However, he indicated construction of the cutoff wall extension is not likely to interfere with fishing in what would have been a restricted area.
Work platform modification, also done by the general contractor, is supposed to start early in October. The platform, originally about 75 feet wide, will be reduced about 20 feet and remain permanently on the upstream side of the dam, Getty said. The lake, currently about 696 feet above sea level, is being lowered to about 690 feet to facilitate the platform reduction work.
Held about 40 feet below normal for six years during rehabilitation of the dam, the lake was allowed to rise 20 feet this past summer after the concrete barrier wall was completed in March. Ancillary work at the dam should be completed by late winter or early spring, Getty said.
Normal operation of the reservoir is expected next summer. If Mother Natural cooperates with plenty of rain, Lake Cumberland should return to pool stage for the 2014 vacation season.
Getty said the contract with general contractor Treviicos-Soletanche JV has been modified to include the cutoff wall and platform modification.