By BILL MARDIS, Editor Emeritus Commonwealth Journal
Completion of the permanent barrier wall in Wolf Creek Dam’s most critical section lacks just 14 more piles, according to Don Getty, manager of the $594 million rehabilitation of the mile-long structure that impounds Lake Cumberland.
A pile is a 50-inch hole, 275 feet deep, filled with concrete. Some 1,432 piles create a concrete wall through the earthen section of the dam. The wall is being inserted to stop uncontrolled seepage that has plagued the structure during most its 62-year history. The barrier wall is done except for the aforementioned 14 piles.
When the wall is complete; when the last pile is in place about the middle of March; when Brigadier General Margaret W. Burcham, commander of the Great Lakes and Ohio River Division, gives the “green light” about a month after the last pile is in place, Lake Cumberland will begin to rise. The Corps said the water level will be allowed to rise 20 feet to between 700 and 705 feet above sea level for this summer’s vacation season.
Tom Hale, operations manager for the lake, said the 20-foot rise will allow water to surround both Pulaski County Park near Nancy and “ ... to the best of my knowledge” will bring the water to the causeway at General Burnside Island State Park.
The extended boat-launching ramp at the state park has been and is in use, but Hale said the additional 20 feet of water will make launching much easier. Pulaski County Park has been “dry-docked” since the lake was lowered 40 feet in January 2007. The water this summer should be high enough around the county park to launch boats.
Because of heavy rains in the Cumberland River Basin, the lake as of noon Thursday was at 692.77 feet above sea level, almost 13 feet higher than the Corps’ mandate of between 680 and 685 while dam repairs continue.
“We are aggressively bringing the water level down to the 680-685 level and will continue to do so until we get permission to do otherwise,” Getty said.
As of noon Thursday, 24,920 cfc (cubic feet per second) were being released through the dam and the lake level was steady after slowly falling.
There are six turbines and six sluice gates at the bottom of the dam through which flow can be reduced to raise the lake level. Spillway or flood gates at the 723 level obviously are not involved, Getty said.
“Mostly, we will depend on spring rains (to raise the lake level),” he said.
There will be little or no noticeable difference in the flow of Cumberland River below the dam while the lake is being raised, according to Getty.
“We must maintain a minimum flow of 1,000 cfc (cubic feet per second) ... a significant amount of water,” Getty said.
Obviously, with nearly 25,000 cfs being released now, Cumberland River below the dam is running high.
Work on the permanent barrier wall is continuing in what is called Critical Area 1, a 600-foot cavern-laced part of the dam near the wraparound of the earthen section with the concrete monolith. It is this unstable area that delayed the rehabilitation project for about a year.
Up to now, three drills have been working in Critical Area 1. However, Getty said at the end of this week there will be space for only one drill to operate. “(Lack of space) will slow us down quite a bit,” he added.
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 is filled with 140 cubic yards of concrete.
The 50-inch holes overlap, like Olympic rings, forming a permanent wall that must be at least 2 feet thick. The new wall extends into a deeper and more stable limestone stratum than immediately below the dam.
About 1,200 piles have formed the now-completed wall in the earthen section of the dam outside Critical Area 1. The wall inside the critical area is formed with 232 piles. Engineers have said the wall must be finished in Critical Area 1 before the lake is allowed to rise.
A narrower work platform on the upstream side of the dam will remain after the project is completed. The platform, created to accommodate equipment to repair the dam, is currently being reduced from 75 feet wide to 55 feet, Getty noted.
Getty said buttress stone will be placed against the temporary wall on the back side of the work platform. It will leave a 30-foot-wide permanent platform across the upstream side of the dam, he said.
Completion of the rehabilitation project and a rise in the water level will end six years of low lake levels that depressed a local economy already hurting from a nationwide recession.
Engineers say the repairs on the dam will permanently stop uncontrolled seepage that in 2005 resulted in the structure being declared in high risk of failure.