A decades-long project to build a new lock to relieve barge traffic congestion on the Tennessee River is making progress.

In early February, the U.S. Army Corps of Engineers Nashville District and contractor Johnson Brothers set the final shell in position on the riverbed after high waters on the river fell to a suitable elevation following weeks of delay.

The final concrete shell is placed on the Tennessee River riverbed on Feb. 2, 2020 below Kentucky Lock. Source: USACE by Lee RobertsThe final concrete shell placement at Kentucky Lock for the downstream cofferdam, which also forms the new lock wall, put the construction project back on track, the Corps of Engineers said. Workers had been waiting since Dec. 18 for the water level to drop far enough to allow the shell to be installed.

Divers were scheduled to seal the base of the concrete shell with sand bags, and construction workers were expected to place “tremie concrete” in the bottom of the shell to cure and form a plug.

The Kentucky Lock Addition Project is located in western Kentucky at Mile 22.4 of the Tennessee River. A 1992 feasibility report recommended a new 110 ft by 1,200 ft lock adjacent and landward of the existing 110-foot by 600-foot lock. Construction began in July 1998.

Credit: USACE by Mark RankinHeavy congestion

Funding for the project was on and off, and the lock was not expected to enter service before the 2040s. That timeline has been accelerated and completion in the mid-2020s is now expected.

A towboat operator can expect to wait about 10 hours for a turn at the lock, then face a multi-hour process of breaking the tow into pieces small enough to move through. Traffic at Kentucky Lock is the most congested of any of the 262 Corps of Engineers locks in the country.

In addition to the new lock, other major project features include: a new two lane bridge for U.S. Highway 62 and a single track bridge for the P&L Railway, Inc. across the Tennessee River just below the dam; five additional new secondary bridges related to the relocation of Highway 62 and the P&L RR; the relocation of four existing east bank Tennessee Valley Authority transmission towers and the construction of four more towers on powerhouse island; numerous other utility relocations; environmental mitigation features; and enhanced tailwater fishing.

Shell placement

The Nashville District placed the first of 10 concrete shells in August 2018. The lift-in technique used to place all 10 concrete shells was done with a gantry crane that was designed and constructed specifically for the downstream cofferdam contract. The crane was used to complete the final lift of the approximate 46 ft wide by 53 ft long by 31 ft high concrete shell, which weighted around 1.7 million pounds.

Project overview. Source: USACEWith the placement of the last concrete shell, the contractor now may build the temporary portion of the downstream coffer dam making it possible to excavate and then construct the new lock in dry conditions. As part of the work, the contractor will install three 69 ft diameter sheet-pile cells to complete the cofferdam, which is around three-quarters complete.

The contractor recently placed 24 ft of concrete on top of five of the shells, raising the level of the future lock wall from 33 to 57 ft. Water overtopped the four other shells in December, delaying work to place concrete over the remaining shells.

Elsewhere on the site, a $55 million excavation contract 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 cofferdam will make it possible to complete the excavation and then build the downstream portion of the lock chamber.

Monoliths contract coming

The Nashville District is preparing to award the Kentucky Lock Downstream Lock Monoliths contract, which is greater than $250 million. 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.