The U.S. Army Corps of Engineers Nashville District placed the 10th and final concrete shell on the downstream riverbed February 2, 2020. Johnson Brothers, contractor for the cofferdam contract, set down the 1.7-million pound shell that is part of the cofferdam and a permanent part of the new lock wall for the Kentucky Dam Lock Addition Project. With the placement, the cofferdam project is 73 percent complete. (USACE video by Leon Roberts)
Transcript
(upbeat music)
The US Army Corps of Engineers Nashville District has reached another huge milestone with the placement of the tenth and final concrete shell for the Kentucky Lock Addition Project. This is the last piece of what will be the permanent lock wall for the new navigation lock. It will also be used as part of the cofferdam in order to do future excavation and construction in the dry.
Johnson Brothers, contractor for the cofferdam project, set the final shell in position February 2, 2020 on the riverbed below Kentucky Lock, where it will be part of the cofferdam and eventually a permanent part of the new lock wall. The placement of the 1.7-million-pound shell took place after the Tennessee River receded to a suitable elevation, following weeks of delays due to high water at Tennessee Valley Authority’s Kentucky Dam.
We’re putting concrete on top of these shells. We’re adding an additional 24 feet of concrete. So, for the first five shells we placed, they were high enough out of the water, we were able to continue to place concrete on those during high water. So, we haven’t been sitting here idle, the problem is we haven’t been working on the critical work during high water, and that’s setting this tenth shell.
[Lee] The contractor emphasized constant communication and attention to safety. Throughout the lift, the main objective involved keeping the shell level and inching it into position because it’s difficult to slow down a heavy weight object, once it gets moving on the water.
We’ll get it close as possible to grade, and then we’ll tug it on into the keyway. Once we get it into the keyway, the divers will assist us hooking up the post tension rods that’s tied back to the previous monolift, that’s already anchored in concrete. That keeps the shell from shifting or moving once we’re set and locked in.
[Lee] The Corps of Engineers placed the first of ten concrete shells August 6, 2018. With each shell placed, the contractor and Army Engineers made communication a priority, to reduce risk and improve methods and processes.
This is a massive undertaking, and it has been since the fall of 2018 to now and February of 2020, to set ten of these. And that just shows that the contractor and the government both worked together and was able to do this.
[Lee] Aspects of the lift and technique used to place all ten concrete shells with a gantry crane, is a unique engineering achievement. The contractor specifically designed and constructed the for the downstream cofferdam contract, and it proved its worth yet again, with a final and heaviest lift.
Once the shell is set in the water and sitting on the spuds and we’ve locked it in with our PT brackets on the side, the contractor has a lot of work to do to pour concrete inside that shell and lock it in place. We’ll come back in, maybe in a week or so, when that work is done and when all of those sandbags are in place, and we’ll pour it, we’ll tremie concrete underwater and fill, what we call the plug, we’ll put the plug in, which sort of locks the shell in place.
[Lee] The temporary portion of the downstream cofferdam is the final step, that will make it possible to excavate and then construct the new lock in dry conditions. This is Lee Roberts reporting for the Nashville District at the Kentucky Lock Addition Project in Grand Rivers, Kentucky. (upbeat music)