By Lee Roberts
GRAND RIVERS, Ky. (March 24, 2020) – The cofferdam at the Kentucky Lock Addition Project is finished, a milestone that paves the way for downstream excavation work to prepare the site for construction of the remaining portion of the new lock chamber.
Jeremiah Manning, resident engineer with the U.S. Army Corps of Engineers Nashville District, said Johnson Brothers Construction, the Corps’ partner on the $68 million downstream cofferdam contract, is working on punch-list items now, but has already turned over the completed cofferdam.
“We had a great big challenging project,” Manning said, referring to challenging river conditions in 2018 and 2019 that resulted in delays to construction progress in about one year of schedule growth. “Hopefully the tide is turning on this project and we’re isolating ourselves from our biggest risk factor, which is the tailwater at Kentucky Dam.”
Johnson Brothers Construction placed the first of 10 concrete shells Aug. 9, 2018 using an innovative lift-in technique, which employed a specially designed floating gantry crane and four spuds to hold the shells in place on the prepared rock stream bed. The contractor placed the final concrete shell Feb. 2, 2020 and altogether the 10 shells form the permanent portion of the cofferdam and the downstream lock wall.
Work progressed in June 2020 to the main construction of the temporary cellular structure of the downstream cofferdam. The contractor installed circular steel sheet-pile structures into the riverbed and put granular fill inside of each one to collectively form a dike.
Jody Robinson, Contract Administration Team lead at Western Kentucky Area Office, said the cofferdam is the most important spot on the job site because its specific purpose is to hold back the tailwater from construction activities.
“This cofferdam is critical to the entire rest of the project,” Robinson said.
Barney Schulte, the project’s lead engineer in the Nashville District’s Engineering and Construction Division’s Structural Section, led the team of engineers that worked on the plans and specifications and whole design of the project. He said he also coordinated integrally with the Construction Office and contractor, including overcoming challenges with preparing the foundation and installing the 10 concrete shells into the river.
“It’s a huge monumental achievement for our contractor. They’ve been out here for several years constructing this. It was a very difficult task for them and the Corps, and it’s a great moment now as we near the completion of this contract,” Schulte said.
At one point during the height of the construction and installation of the concrete shells, Johnson Brothers Construction had about 150 people on the job site, including sub-contractors, which made for a very busy construction zone.
Jamie Willcutt, construction manager for Johnson Brothers Construction, said his crews have done an incredible job under difficult conditions, and the team has been working around the clock over the past year to complete the cofferdam.
“Everything has come together fairly nicely. We’ve had some adversity but overcome it,” Willcutt said. “This is a highly technical and highly engineered project… so to be where we are at is amazing. I probably won’t build another one of these in my lifetime, so to just be a part of it and to work with the Corps has been great. It’s been an amazing journey.”
Heeter Geotechnical Construction, contractor for the $58 million downstream excavation contract, is already installing a grout curtain into the cofferdam. Once this grouting is completed, water behind the cofferdam can be pumped out, making it possible to excavate in dry conditions.
Robinson said Heeter has already been busy excavating in areas more upstream near the completed portion of the upstream lock chamber but can now excavate across the entire construction footprint.
The Nashville District’s team at the Kentucky Lock Addition Project have been working alongside its agency partner, the Tennessee Valley Authority, which also provides expertise and input on this construction project. Throughout the project, the Corps’ team from the headquarters down to the construction site have been overcoming obstacles and challenges to minimize delays and deliver the project for the American people.
“The team successfully avoided a significant amount of the time and cost impacts associated with the project schedule through the phased turnover of the cofferdam and other initiatives that have allowed both contractors to continue progressing their work,” Manning explained.
Manning said the Nashville District is working on design and acquisition for the next phase of the project and plans to bid the Downstream Lock Monoliths Contract this year. This contract will structurally finish the new lock’s chamber and place all the remaining concrete for the new 110-foot by 1,200-foot navigation lock at the TVA project. The contract period will be roughly 60 months and includes limited rock excavation, placement of about 400,000 cubic yards of concrete in the construction of 51 lock monoliths, fabrication and installation of downstream miter gates, grouting the lock wall foundation, backfill of one million cubic yards of soil, and fabrication and installation associated with mechanical features of the new lock.
