Commonwealth Journal

August 3, 2013

Cutoff wall to prevent erosion at Wolf Creek

Project unrelated to repairs on dam

by Bill Mardis
Commonwealth Journal

Somerset —

Construction of a cutoff wall is under way to prevent erosion from undermining the electrical switchyard near the base of Wolf Creek Dam.
Don B. Getty, manager of the Wolf Creek Dam Rehabilitation Project, said the contract with Treviicos-Soletanche JV, general contractor for the rehabilitation project, has been modified to include the cutoff wall work.
This project 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.
Many believe the condition of Wolf Creek Dam during the late 1960s was more serious than in 2005 when the dam was declared in high risk of failure. Intensive grouting slowed the seepage, and a cutoff wall, not long enough and not deep enough, was installed during the 1970s. A just-completed, $594 million rehabilitation of the dam is believed to be a permanent fix for the uncontrolled seepage problem.
The new section of cutoff wall will be 180 feet long and constructed by drilling 50-inch overlapping holes, same as the 4,000-foot-long permanent concrete barrier wall was inserted in the dam during the past six years. The cutoff wall near the switchyard won’t be as deep as the 275-foot-deep wall in the dam, Getty noted.
Engineers believe there is a connection between fluctuation of tailwaters and undermining the switchyard area, Getty said. “This extended cutoff wall near the switchyard has absolutely nothing to do with the lake,” Getty emphasized.
The second barrier wall in the earthen section of the dam was completed in March and the lake was allowed to rise 20 feet above the target operational level during the six-year rehabilitation of the dam. The lake, pending another safety review, is scheduled to return to historical operation next year.
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.