Replacement dam unlikely

By BILL MARDIS Editor Emeritus

June 15, 2007 09:18 am

— A roller-compacted concrete dam to effectively replace the earthen section of troubled Wolf Creek Dam apparently is becoming less likely as time draws nearer for a final report on a feasibility study of the massive rehabilitation project.
Dave Treadway, public affairs specialist for the U.S. Army Corps of Engineers’ Nashville District, told the Commonwealth Journal this week that “ ... all indications point to a diaphragm as the most feasible, most cost effective, most workable plan.” He said a final report on the current study probably will be made the last of June.
“The report will give us enough information so we will know if we can rule out (a roller-compacted dam),” Treadway said. “If such a new dam appears feasible, more work will have to be done,” he added.
A diaphragm -- a four-to-five-foot-thick concrete wall extending through the earthen section of the dam and some 100 feet into the bedrock below the dam -- is the original plan and the one for which preparations currently are being made.
A contract for a diaphragm is tentatively scheduled to be let in December. It would be the second concrete wall extended through the earthen section of the dam. However, the diaphragm built during the 1970s was not as long or as deep as the planned structure.
A roller-compacted dam would be constructed with layers of concrete, each compacted with heavy equipment. The structure would be immediately downstream from the existing earthen section and would tie in with the existing concrete part of the dam. The earthen dam would remain and U.S. 127 across the dam would be undisturbed, according to early reports.
Lt. Col. Steven J. Roemhildt, commander of the Corps’ Nashville District, recently told the Commonwealth Journal that a roller-compacted dam would require lowering the lake level much lower than now, a situation unacceptable in a region where the economy is tied closely with the lake. He said the proposed diaphragm “will provide a permanent fix until the end of the (21st) century.”
Treadway, after discussing the new-type dam with Mike Zoccola, chief of the Corps’ Civil Design Branch, said building a roller-compacted dam would require “shutting down Wolf Creek Dam as we know it today ... and refilling the lake.”
“Would that mean draining the lake?” a reporter questioned.
“Basically,” responded Treadway. He said a completed roller-compacted dam would mean the entire length of the mile-long dam would be concrete. There apparently are no problems in the existing concrete section.
Lake Cumberland has been operating at 680 feet above sea level, about 43 feet below normal, since January. The water was lowered to ease pressure on Wolf Creek Dam, classified as in “high risk” of failure by a panel of outside experts.
Treadway said the drought in the Cumberland River Basin “ ... is actually helping” to maintain the current lake level. Pointing out that the Corps is required by law to keep nine feet of water in the navigable channel of the Cumberland River, Treadway said part of this mission has been taken over by Dale Hollow Lake.

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