Somerset —
Rehabilitation of Wolf Creek Dam is 89 percent complete and work is going “ almost too smoothly,” according to the project manager.
“But that’s a good thing,” laughed Don B. Getty. He said only two piles remain to be done in the earthen area of the dam outside Critical Area 1, and about 120 more piles need to be formed in the critical area. In other words, a permanent barrier wall to stop uncontrolled seepage is nearly complete except in the most critical area near where the earthen section joins the concrete monolith.
The permanent wall is being created by drilling 50-inch diameter holes 275 feet deep from the work platform on the upstream side of the dam to about 100 feet into the limestone bedrock. Each hole, filled with 140 cubic yards of concrete, is called a pile. About 1,200 piles have formed the wall outside Critical Area 1.
The 50-inch holes overlap, like Olympic rings, forming a permanent wall that must be at least two feet thick. The new wall extends into a deeper and more stable limestone stratum than immediately below the dam. Another wall, installed during the 1970s, was not long enough or deep enough to stop uncontrolled seepage that undermined integrity of the structure.
The earthen section of the dam is about 3,800 feet long and the concrete section through which the six hydroelectric generators operate extends the entire length of the dam to about a mile. U.S. 127 crosses atop the structure that impounds Lake Cumberland.
Critical Area 1 is undermined with caverns in the limestone base. The area initially wouldn’t retain grout (chemically treated liquid concrete) and ended up delaying the rehabilitation project about a year.
“The work will slow down once we finish the section outside the critical area,” said Getty. “We’ve been using five drills but only two drills work in the critical area,” he noted.
“The barrier wall must be completed before we can raise the level of the lake,” said Getty. The projected date for finishing the barrier wall is December 2013. Then the lake will be raised in increments and each level monitored by some 350 instruments in the dam. As soon as engineers are sure each water level is safe, the lake will be raised to a higher level and checked again.
“It’s unlikely the lake will be at historical levels in Summer 2014, but it will be significantly higher than it is now, Getty said. The lake has been held as nearly as possible to 680 feet above sea level, about 40 feet below normal, since January 2007.
Getty said no significant problems have developed while drilling in Critical Area 1. “But we keep our fingers crossed ... it is a critical area,” he reminded.
Seepage has been a problem since the dam was built. A panel of experts in 2005 labeled Wolf Creek Dam in high risk of failure. Treviicos-Soletanche JV, a joint French-Italian company was given a contract to fix the dam, a project of size and complexity never before done.
David Hendrix, previous project manager, said U.S. Army Corps engineers today would have never built Wolf Creek Dam at its location. “If we had built it here, we would have excavated the entire limestone base,” he said.
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