The Corps of Engineers announced Jan. 22 it will lower the level of Kentucky’s Lake Cumberland to reduce the risk of Wolf Creek Dam failing.
The Corps said it will spill water and release water through the project’s 270-MW powerhouse over about two weeks to reach a target level of 680 feet. By reducing water pressure on the dam, the Corps said it can lessen the risk of dam failure and limit seepage through the dam foundation.
The Corps already was carrying out rehabilitation work to address the seepage problem. However, it decided to reduce the water level further based on its own recent studies and independent studies following Hurricane Katrina.
Those studies classified Wolf Creek Dam as being at ï¿½high riskï¿½ for structural failure. However, the Corps said the dam is not in imminent danger of failing.
ï¿½A high level of risk does exist,ï¿½ District Commander Lt. Col. Steven Roemhildt said. ï¿½Reducing the lake level lowers pressure on the dam and the pumping of grout into the ground lessens erosion, both of which immediately reduce risk.ï¿½
The half-century-old dam has experienced foundation seepage for years. However, the Corps said pressure from water in the reservoir eventually eroded soil-filled spaces in the rock beneath the dam. Citing the seriousness of the foundation seepage, the Corps said it is accelerating the grouting program. It said lowering the lake level would simplify grouting work.
Funding sought to accelerate construction
The Corps said it will request full funding to $309 million from Congress to accelerate construction of the remedial project, which includes not only grouting but construction of a concrete diaphragm wall to reinforce the original wall. The work could take 10 to 12 years, a Corps spokesman said.
The Nashville District awarded a construction contract in December 2006 for grouting work, already in progress. (HNN 6/19/06) Advanced Construction Techniques Ltd. of Kettleby, Ontario, is carrying out the $14 million contract, pumping grout into areas to control seepage.
The Corps has operated the reservoir since March 2005 to maintain lake levels within a lower range. It will maintain the 680-foot elevation for the remainder of 2007. It plans to re-evaluate lake levels in September or October for 2008 operation. Dam safety experts will monitor conditions and further reductions might be necessary, depending on how lower lake levels affect the dam.
The 5,736-foot-long, 258-foot-tall rolled earthfill and concrete gravity dam is located in Kentucky and impounds the largest reservoir east of the Mississippi River. (HNN 6/26/06) Normal pool levels are 723 feet in summer and 690 feet in winter.
While the lower lake level is expected to reduce generation at Wolf Creek, the Corps said it could make up for losses by increasing generation at other hydro projects in its system. Additionally, fossil generation could make up some losses.