By Leon RobertsAugust 10, 2018
GRAND RIVERS, Ky. (Aug. 9, 2018) - The U.S. Army Corps of Engineers Nashville District successfully placed the first 1.3 million pound concrete shell on the riverbed Aug. 6 that will be part of the downstream cofferdam and the permanent lock wall for the Kentucky Lock Addition Project.
Unforeseen challenges extended the placement of the concrete shell from two days to five, but the effort could have taken much longer if not for the engineering expertise and teamwork between the Corps of Engineers and the project's contractor partner, Johnson Brothers.
A tow boat moved the barge with the concrete shell into position underneath the gantry crane just below the existing Kentucky Lock late afternoon Thursday, Aug. 2. After preparing the heavy load for lift off the next day, the contractor raised the shell from its barge, but did not have time to move the shell into its final position. On Saturday, Aug. 4, during the final life, a problem developed in the lift system. Engineers honed in on one of four strand jacks on the gantry crane and then worked Saturday afternoon until early Monday morning to complete repairs. These repairs included modifying specialty bolts that were damaged Saturday.
Crews successfully picked up and set down the 46-foot wide by 51-foot long by 33-foot high concrete shell Aug. 6, the first of 10 shells to be placed.
Don Getty, U.S. Army Corps of Engineers Nashville District's project manager for the Kentucky Lock Addition Project, said the challenges everyone faced with the heavy lift were not taken lightly, as all involved took the necessary time to make sure the lift system operated as designed so the shell could be placed safely.
"The learning curve on a new, unique, and complicated construction technique is steep," Getty said. "We believe that aspects of this lift-in design have never been attempted."
Once all of the technical issues with the lift system were resolved early Monday morning, the gantry barge moved the concrete shell about 200 yards to position itself in the set-down location. While the team moved the concrete shell into position there were other obstacles that had to be overcome.
Getty said an unanticipated underwater obstruction encountered 4 p.m. Monday prevented the shell from lowering into position, essentially leaving the operation dead in the water.
"Kentucky Lock's lead engineer, Barney Schulte, and construction engineer, Jody Robinson, developed a simple and elegant solution that was coordinated and accepted by the contractor in about an hour," Getty explained. "By 5 p.m. on Monday, the contractor was back at work lowering the shell into the water onto a prepared foundation on the bedrock. Crews finished its placement near midnight and Kentucky Lock reopened to barge traffic soon after."
Jeremiah Manning, resident engineer for the Kentucky Lock Addition Project, lauded his team of onsite construction managers and the contractor partner, which set the first concrete shell and are working together to deliver the program for the downstream cofferdam project.
"The lift-in technique that we're using here in itself is unique. There are aspects that haven't been done anywhere else," Manning said. "I want to applaud the efforts of Johnson Brothers... which worked through numerous challenges and brought the technical expertise to solve problems and maintain a schedule to get us where we are today."
Both the Corps and contractor overcame unexpected hurdles during the placement of the first concrete shell, and look forward to improving processes from the experience.
"As expected, this unique and first-time event was full of challenges. The good news here is nothing got in our way of achieving success," Getty said. "We have a lot of lessons learned that should make the next nine shells go much faster."
With the first concrete shell in position, it will be sealed and then filled partially with "tremie concrete," placed through a pipe underwater to the bottom of the shell to cure. All told, about 11 million pounds of concrete will be placed to fill the shell.
The Corps is constructing the new navigation lock at Kentucky Dam to reduce the significant bottleneck that the 600-foot-long current lock causes on this important waterway. Because of high Tennessee River traffic levels and the current lock's size, the average delay times for commercial tows going through Kentucky Lock average from eight to 10 hours - near the highest in the country.
When completed, the downstream coffer dam will make it possible to excavate and then construct the new lock in dry conditions.
"Reaching this point in the project is a monumental accomplishment that is a testimony to a lot of hard work by the Kentucky Lock Team," said Lt. Col. Cullen Jones, Nashville District commander. "The Corps, our partners at Tennessee Valley Authority, and our contractor, Johnson Brothers, have been working very well together to overcome the many challenges facing them on a project of this magnitude to make this day happen."
The total cost for the Kentucky Lock project is $1.25 billion with about $455 million expended to date, or about 36 percent complete. Funding bottlenecks that have plagued the project since construction commenced in 1998 have been lifted in the last three years. This has allowed progress to proceed full tilt for the downstream cofferdam and has allowed the advertisement of the next large construction contract for the project, the Downstream Lock Excavation. This contract is expected to be awarded by Sept. 30, 2018.
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.