"Critical Area #1 is unquestionably the key to this project," says Project Manager David Hendrix.
Hendrix leads the team that is now building a giant concrete wall along the dam 275ft deep into the earth. The wall will hold back the lake waters, and grout is being used to fill voids in the limestone. Even after several years of construction, the Corps is still drilling samples and finding large empyt spaces under the earthen embankment. Even after several years of construction, the Corps is still drilling samples and finding large empty spaces under the earthen embankment.
"Either no rock or no mud or no soil in a zone," says Geologist Mark Hostetter. "So, this is apparently a cavity."
While much of the construciton is well underway, only a small amount of work has been completed in Critical Area #1, the dam's weakest point. Monitors and guages have shown the work is putting too much pressure on the dam. For much of the last year no work was done in that section.
"We have our instruments of different types on the dam that we monitor 24/7," says resident engineer Kathy Lusk.
The Corps is just now beginning to proceed cautiously in Critical Area #1 to finish the grouting and build the wall that's so essential.
"Very much like operating on a live patient," says Lusk. "When we push, he feels it."
This project is the Corps' top priority. If it were to fail, the consequences would be devastating.
"So, this is basically the whole county," says Metro OEM Deputy Director Kevin Penney.
Nashville's Office of Emergency Management knows the risks. If the dam breaks, hundreds of billions of gallons of water could pour into the Cumberland River, rushing downstream and flooding every town, including Nashville, along its path. 7 days after the dam breaks, water in downtown would rise 2-8ft higher than the May 2010 flood.
"Identify the key areas and critical facilities," says Penney.
The Office of Emergency Management has developed a comprehensive plan to respond to this unthinkable disaster.
"With these plans in front of us, and the training that has occurred, we'd be able to address those needs well within the time frame of it affecting Nashville," says Penney.
As work continues at Wolf Creek, the Army Corps is confident the dam will hold.
"There's no question that the structure is safer than it was when we started," says Hendrix.
The job won't be done until at least December 2013, and instead of finishing Critical Area #1 first, it will now be the last section completed. The goal is to preserve the beauty of the river and cities below by protecting the dam that guards them above. In order to reduce pressure on the dam, the Corps continues to lower the level of Lake Cumberland. Right now, the lake is at 711ft above sea level. The Corps would like the lake to be about 30ft lower at 680ft.
Monday, July 25 2011, 01:07 PM CDT
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