by Bill Mardis
Lake Cumberland may soon be allowed to rise about 15 feet, to 705 feet above sea level, same as last summer. However, a green light has not been given for the lake to return to normal operation.
“It is our goal to return the lake to historical operation by this spring, but whether it returns to 723 feet (pool stage) this summer will depend on Mother Nature (sufficient rainfall),” said Don B. Getty, manager of the $594 million rehabilitation of Wolf Creek Dam.
The green light for normal operation, when it comes, will be given by Brigadier General Margaret W. Burcham, commander of the Great Lakes and Ohio River Division of the Corps. Getty emphasizes there are hurdles and challenges ahead before official OK is given for normal operation.
Apparently all is well. Instrument readings and visual observations of Wolf Creek Dam continue to indicate the recently completed rehabilitation of the mile-long structure is a quality job, Getty indicated.
The Nashville District of the U.S. Army Corps of Engineers currently has permission to raise the lake to 705 feet above sea level, Getty noted. “We expect to allow the lake to rise to this level soon,” he said Tuesday.
The lake has been kept as closely as possible to 690 feet since last fall to facilitate mop-up work on the face of the dam. The level Thursday morning was 690.08.
Getty said the Great Lakes and Ohio River Division, headquartered in Cincinnati, is working with the Nashville District but Commander Burcham does not yet have the full package of information on which she will base her decision.
During the second week of December a panel of experts, called a Vertical Team, held a two-day final review of the rehabilitation project and took a field trip to the dam. Getty said the review by the Vertical Team went “really well.” However, he strongly emphasizes a lot of challenges remain.
Alluding to Getty’s references to hurdles and challenges, a reporter asked Getty: “Has anything happened to make you worry? Has anything happened to make you happy?”
“By nature, I’m a worrier,” Getty laughed. However, Getty said there is nothing to indicate rehabilitation of the dam is not a success.
Wolf Creek Dam is probably the most instrumented dam in the world. About 250 piezometers -- instruments to measure static liquid pressure –– are installed in the dam. Getty says none of these instruments has given readings to cause concern since the permanent concrete barrier wall was completed last March.
Engineers walk the dam five days a week, eight hours a day, visually inspecting the structure. Prior to completion of the barrier wall, visual inspections were done around the clock, seven days a week.
The barrier wall inserted during the last seven years is touted as a permanent fix for the dam. The wall, created by drilling overlapping 50-inch-diameter holes filled with concrete, extends about 100 feet in bedrock below the dam. Engineers said enough concrete was put in the dam during the recent rehabilitation project to build a sidewalk 5 feet wide from the dam site to Washington, D.C.
Work is continuing on the face of the dam to remove shotrock and replace it with riprap, Getty noted. He said this project was held up about a month by a high lake level but is expected to be finished by early February.
Also, a cutoff wall is being extended to protect the electrical switchyard immediately below the dam. This project is ahead of schedule, Getty said.
Other current work at the dam site includes narrowing the work platform, created to accommodate heavy equipment, from 75 feet wide to a permanent passage 30 feet wide, and redesigning the intersection with U.S. 127 and the road leading below the dam.
Lake Cumberland has been plagued with uncontrolled seepage since the gates were closed at Wolf Creek Dam in December 1950. A major crisis during the late 1960s was temporarily fixed with grouting (pumping liquid concrete into the dam) and insertion of a not-deep-enough and not-long-enough barrier wall during the 1970s.
The dam in 2005 was declared in high risk of failure. Beginning in 2007, another barrier wall, 4,000 feet long and 275 feet deep, was inserted in the earthen section of the structure. The lake was kept about 40 feet below normal for six years to facilitate the repairs. Last summer, with the concrete barrier wall in place, the lake was allowed to rise to between 700 and 705 feet above sea level during the recreational season.