Published: May 27, 2009 10:29 pm      

Wolf Creek Dam protective wall coming along as planned

The first 30 panels of a protective concrete embankment wall have been installed in Wolf Creek Dam, according to the latest report on the U.S. Army Corps of Engineers’ website.

The protective concrete embankment wall is the first construction phase of a permanent barrier wall designed to stop uncontrolled seepage in the mile-long structure that impounds Lake Cumberland.

Each panel of the preliminary wall is approximately 10 feet long and 4 feet wide. The panels are being installed by excavating with a hydromill and backfilling with concrete.

Purpose of the protective concrete embankment wall is to stabilize the earthen section of the dam during insertion of a permanent concrete barrier wall. The preliminary wall will extend downward to the top of the limestone bedrock.

David Hendrix, project manager at the U.S. Army Corps of Engineers’ Nashville District, told the Commonwealth Journal that specifications of the permanent diaphragm wall have a minimum requirement of at least two feet thick. It will be 4,200 feet long and extend 300 feet through the earthen section of the dam into the bedrock. Depth of the wall will vary but will be about 75 feet deeper than a wall inserted during the 1970s in an effort to stop a more serious leak that developed in the late 1960s.

“We’re taking the (new) wall down to the Catheys Formation,” said Hendrix. He explained that this is more competent limestone rock than the Leipers Formation, a karst limestone region beneath the dam that is marked by sinkholes and interspersed with abrupt ridges, irregular, bulging rocks, caverns and underground streams. Seepage through this karst causes the dam to develop serious leaks.

Mike Zoccola, chief of the Civil Design Branch for the Corps’ Nashville District, said the preliminary wall currently being inserted will remain in the dam, adding stability to what engineers say will be a permanent fix for the troubled structure that was declared in high risk of failure early in 2005. A $341.4 million contract has been awarded to Treviicos Soletanche JV, a joint Italian-French company, to repair the dam.

Critical Area No. 1 — where the earthen section joins the concrete section of the dam — will be sealed by spring of 2010, Hendrix indicated. This is the area of most serious seepage that could not be closed by grouting.

Although no one said so specifically, the fact that grouting could not stop seepage at Critical Area No. 1 is likely the reason LTC Bernard R. Lindstrom, commander of the Nashville District, said there is no chance of a rise in the lake level until –– “hopefully, hopefully, hopefully” –– spring of 2010. The lake has been held more than 40 feet below pool stage since January 2007 to ease pressure on the seepage-plagued structure.

Total cost of rehabilitating the dam is estimated at $584 million. The project is scheduled for completion in October 2012.