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A lock on the Tennessee River that was originally built in 1944 will double in length as part of an ongoing expansion project expected to be completed by July 2027.
The Kentucky Lock is undergoing a $1.5-billion overhaul that will see it expanded to 110’ x 1,200’ with an addition adjacent to the existing lock. According to a recent Engineering News-Record article, the existing lock will remain operational once the project is completed.
The U.S. Army Corps of Engineers, which is managing the project, said that once completed, the increased capacity of the expanded lock will alleviate current delays for vessels that average 10 hours – the highest of all U.S. locks.
Key to this western Kentucky construction project are 64 structural monoliths which form the lock’s core. The first of these monoliths topped out in October 2024.
According to ENR’s reporting, the 100-acre construction side for the Kentucky Lock Addition project features a concrete batch plant, thousands of feet of a material conveyor system and specially built fabrication shops to manufacture elements needed for the monoliths.
Thalle Construction Co., a Tully Group company based in Hillsborough, North Carolina, is constructing and installing the remaining structural components necessary to complete the new lock, which the Corps says will provide an economic benefit of roughly $114.3 million a year.
Thalle Project Executive Brian Sharp told the publication that constructing each monolith demands approximately 11,000 cubic yards of concrete to form the lock’s walls. Once completed, the structure will house an array of large valves, culverts, and ports designed to regulate the flow of water from Kentucky Lake into and out of the lock chamber, allowing vessels to move both upstream and downstream.
“Each monolith is essentially a massive concrete block,” Sharp said. “The monoliths are founded on a prepared bedrock surface and extend to the top of the lock.”
These blocks average 50 ft. in length, 110 ft. in height and vary in width between 75 ft. at the bottom and 25 ft. at the top.
“The monoliths are constructed in five-foot vertical increments and require up to 23 placements to complete,” Sharp says. “These five foot heights are referred to as lifts and represent individual concrete placements.”
Kenneth Bowen, project executive at Thalle, notes that, “altogether, the 51 monoliths needed to complete the downstream portion of the lock within our scope involve more than 1,200 separate concrete placements.”
Beyond the concrete, each monolith is reinforced with steel and incorporates numerous embedded fabricated metal components, including wall armor, line hooks, floating mooring bits, and internal features such as culvert liners, valves, and mechanical systems essential for operating the massive miter gates.
Thalle’s involvement with the lock began in 2010, following a contract award for site excavation, construction of nine upstream monoliths, and installation of the upstream miter gates. That initial phase concluded in 2016, and the company was awarded the current phase of work in 2021.
Bowen told ENR that ensuring each monolith is on stable ground has been a challenge throughout the Kentucky Lock project.
“Construction of each monolith starts at the foundation, where rock is blasted to a consistent elevation that is inspected and deemed competent to support the massive structure,” he said.
Many of the foundations demand thorough preparation, which involves rock cleaning, dental excavation, and filling surface irregularities with dental concrete before placing a concrete mud mat to finalize the foundation work.
In situations where subsurface geotechnical analysis indicates the need for further reinforcement, Thalle drills as deep as 60 feet into the bedrock and installs steel shafts encased in concrete to enhance structural support, Bowen explained.
How to Keep Your Infrastructure Projects On Time, On Budget, and Safe
The Kentucky Lock project is a critical part of America’s ongoing efforts to improve its inland waterway infrastructure, which received a C- rating in the American Society of Civil Engineers’ (ASCE) 2025 Report Card for America’s Infrastructure.
In that report, the ASCE referred to inland waterways as the “hidden backbone of the nation’s freight network, noting how $158 billion worth of goods move through it annually.
“Inland waterways allow commodities to move cost-effectively, reducing the strain on congested roadways and rail systems, and with fewer greenhouse gas emissions,” the ASCE wrote. “Federal funding has increased in recent years, but a $7.5 billion backlog for construction projects remains, causing ongoing lock closures.”
While the C- rating inland waterways received in the ASCE’s latest report card is an improvement over the category’s D+ rating in the organization’s previous evaluation, there is still plenty of room for improvement:
- 80% of the nation’s lock and dam infrastructure on the inland waterways system exceeds its 50-year design life
- The advanced age and lack of capacity of most of the U.S.’s lock and dam infrastructure has resulted in an average delay of nearly three hours for vessels that rely on the inland waterways system
- And increasingly unpredictable water levels and draught within this system exacerbate these issues for larger craft such as barges, which can’t be loaded to full capacity just in case they encounter shallow waters along their journey
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Frequently Asked Questions
Does GPRS Perform S.U.E. Work?
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