GRAND RIVERS, Ky. (Feb. 2, 2020) – The final concrete shell placement at Kentucky Lock for the downstream cofferdam, which also forms the new lock wall, took place today, a milestone that put the construction project back on track.
The U.S. Army Corps of Engineers Nashville District and Johnson Brothers, contractor for the cofferdam, set the final shell in position on the riverbed after high waters on the Tennessee River receded to a suitable elevation following weeks of delays.
“This last shell is on the critical path for the project, so every day we had to delay placing the shell, we delayed the completion of the project by one day,” said Don Getty, Nashville District’s project manager for the Kentucky Lock Addition Project. “We’ve been waiting since Dec. 18 for the water level to drop to where we could place the shell.”
In the next week, divers will seal the base of the concrete shell with sand bags and construction workers will place “tremie concrete” in the bottom of the shell to cure and form a plug.
The Nashville District placed the first of 10 concrete shells Aug. 6, 2018. Aspects of the lift-in technique used to place all 10 concrete shells with a gantry crane is a unique engineering achievement.
Barney Schulte, the project’s lead engineer, explained that the gantry crane was designed and constructed specifically for the downstream cofferdam contract, and proved its worth with the final lift of the approximate 46-foot wide by 53-foot long by 31-foot high concrete shell.
“Many factors went into its design, most importantly its lifting capacity had to be large enough to lift the largest shell, which weighs approximately 1.7 million pounds,” Schulte said. “The footprint of the crane had to fit in a tight construction space while also fitting under the highway and railroad bridges immediately downstream.”
Jody Robinson, project engineer and Contracting Officer’s representative for the Kentucky Lock Addition Project, said the final lift went smoothly due to the super team effort of onsite construction managers and the contractor.
“Now we will send divers down to hook up cables to pull the shells together, then drop the spuds,” Robinson said. “The spuds are what actually hold the weight of the shell.”
Robinson said teamwork between the Corps of Engineers and the contractor, Johnson Brothers, has been the most important aspect of the successful project.
“Everybody had to work together on months and months of paperwork submittals, multiple meetings, and lessons learned,” Robinson said. “Every process out here has improved. Safety has improved. Every time we learned something we adjusted, accounted for it.”
The water level below Kentucky Dam, a Tennessee Valley Authority project, reached elevation 318 Saturday night, enabling the Corps of Engineers to place the final concrete shell Sunday. Coupled with temperatures in the 60s, it made for perfect conditions to get the job done.
Manuel Salinas, Johnson Brothers job site superintendent, said everything went according to plan with placing the final and heaviest shell.
“My foreman and our crews were on top of their game,” Salinas said. “Everybody was listening and paying attention and everything went really smooth today. I’m really happy with the operation.
Salinas said the team really paid a lot of attention to safety given the weight of the shell. He added they had to keep the shell level and move it in slowly because it’s hard to slow down a heavyweight object once it gets moving on the water.
With the placement of the last concrete shell, the contractor can now construct the temporary portion of the downstream coffer dam, the final step that will make it possible to excavate and then construct the new lock in dry conditions. The contractor will install three 69-foot diameter sheet-pile cells in the near future to complete the coffer dam, which is now 73 percent completed.
The contractor recently placed most of the 24 feet of concrete on top of five of the previously placed nine shells to raise the level of the future lock wall from 33 to 57 feet. Water overtopped the four other shells around Dec. 20, so the contractor is prepared to continue placing concrete on the remaining shells.
Getty said work is ongoing elsewhere on the site. The $55 million excavation contract, which began in September 2018, is stabilizing the existing lock land wall and removing soil and rock from behind it. The contractor also demolished abandoned bridges and the lock maintenance building. When completed, the downstream coffer dam will make it possible to complete the excavation and then construct the downstream portion of the lock chamber.
“Soil excavation that can be performed before the cofferdam is complete is ongoing and rock excavation is expected to commence this spring,” Getty said. “The final stages of soil and rock excavation cannot be completed until the downstream cofferdam is completed.”
The total cost of the Kentucky Lock Addition Project is $1.22 billion, with about $490 million expended to date. The project is about 40 percent complete.
The Nashville District is preparing to award the Kentucky Lock Downstream Lock Monoliths contract, which is greater than $250 million. Interested businesses can meet Nashville District officials and get more information at the Kentucky Lock Downstream Lock Monolith Industry Day 9 a.m. (CST) March 3, 2020. The event is taking place at the Grand Rivers Community Center located at 155 W. Cumberland Ave. A site visit to the Kentucky Lock Addition Project construction site will follow at 1 p.m. Advance registration is required by sending a Nashville District Security Access Form to Contract Specialist Jessica Baker at Jessica.firstname.lastname@example.org not later than three business days prior to the event.
The contract period is 56 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, construction of two bridges across the navigation locks, grouting the lock wall foundation, backfill of one million cubic yards of soil, and fabrication and installation of 17 mooring bits.
The public can obtain news, updates and information from the U.S. Army Corps of Engineers Nashville District on the district’s website at www.lrn.usace.army.mil, on Facebook at http://www.facebook.com/nashvillecorps and on Twitter at http://www.twitter.com/nashvillecorps. The public can also follow Kentucky Lock on Facebook at http://www.facebook.com/kentuckylock.