By BILL MARDIS, Editor Emeritus Commonwealth Journal
“As of (February 19) we had only four more holes to drill.”
Don Getty, manager of the Wolf Creek Dam Rehabilitation Project, gave the update Wednesday. He said the permanent barrier wall to stop uncontrolled seepage in the mile-long structure that impounds Lake Cumberland will be finished by the last of next week or early the following week.
The last four holes to which Getty referred are in Critical Area 1, a 600-foot-long, cavern-laced section of the dam near where the earthen part joins the concrete. The holes, called piles, are 50 inches in diameter and 275 feet deep. Overlapping, like Olympic rings, the holes are filled with concrete to form the barrier wall.
Critical Area 1 was the most troublesome part of the dam to fix. It was laced with caverns, some 40 feet in width. Drilling in this unstable section made for an uneasy situation and it actually delayed completion of the project for nearly a year.
Completion of the barrier wall in Critical Area 1 is key to allowing the lake level to rise. The U.S. Army Corps of Engineers announced about a month ago the lake would rise 20 feet, to between 700 and 705 feet above sea level for the coming summer vacation season.
“April 1 is the best estimate for the dam gates to be closed to allow the lake to begin to rise,” said Getty. “We will be in a series of meetings (the second week in March),” he added. Brigadier General Margaret W. Burcham, commander of the Great Lakes and Ohio River Division, will give the green light for the lake to rise.
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.
There is still work to be done after the permanent barrier wall is completed. A narrower work platform on the upstream side of the dam will remain after the project is done. 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.