© Clinton County News

In Thursday, July 31, 2008 issue

Just three days before last week’s meeting, the Corps of Engineers awarded the contract for construction of what will eventually be the fix for the ailing structure, the concrete cutoff wall that will extend the entire length of the dam, at a depth of at least 250 feet below the foundation.

It’s a massive undertaking, and both Lindstrom and Wilson were quick to agree that there will be problems, but they were also both quick to point out the degree of confidence they had in the Corps’ abilities to correctly assess and overcome any obstacles that might arise during the next portion of the project.

Lindstrom noted that as much as anything else, the contract was awarded on the basis of the firm’s “technical ability” adding that the construction firm was “world renowned for what they do.”

Still, the project ahead will be filled with a lot of “firsts” for both the Corps as well as the contractor completing the project.

“This is going to be a learning process for these guys - they’ve built the biggest walls in the world and they’ve built the longest walls in the world, but they’ve never built one this deep and this long, so we want to make sure they are in the right position to succeed and not to fail,” Lindstrom said. “They’ve never performed in this type of condition totally, so its going to be a challenge.”

Wilson pointed out that before the contractor would begin approaching the area referred to as “critical area one” they would first construct two separate “test sections” of the concrete cutoff wall, located a considerable distance apart in areas where different types of foundation material was known to exist.

These two test sections would allow the Corps to see what methods the firm would use to attack the two totally different scenarios.

After the two test sections had been completed, the work would then immediately move to the critical area one where the concrete and earthen sections join together.

Wilson further stressed, however, that the test sections would not involve the area referred to as “critical area one.”

Wilson also noted that while the construction contract called for a four year “performance period” for the work to be completed, that didn’t necessarily mean that the work would be completed four years from the date the project got underway.

“If we had a major rain event that went on for months and he (contractor) couldn’t work, that time would be added to the contract,” he said. “He also has the option of being finished in three years if he wants to.”

Both Lindstrom and Wilson pointed out the differences in the process of installing the grout curtain as opposed to the process of constructing the deep concrete barrier wall.

Because of those differences, when “closure” is eventually reached as far as the seepage in the area where the concrete and earthen sections join, it might be possible then that Lake Cumberland will experience some increase in water levels.

While officials lowered the lake level to reduce pressure against the dam during the grouting process, they pointed out that lower lake levels won’t necessarily be called for in the cutoff wall construction process.

“We won’t have to lower the lake to reduce the foundation pressure to install the wall,” Lindstrom said. “There’s nothing in the construction process of the cutoff wall that would require us to lower the lake.”