Tugboats traveling the Tennessee River carry millions of pounds of goods along the waterway every year – and a lot of it goes through the Kentucky Lock.

The key piece of infrastructure acts as a gateway for river traffic, allowing vessels to access both the Tennessee and Cumberland river basins, as well as the Ohio and Mississippi rivers.

In recent decades, though, it’s become a place where river traffic gets jammed up. Delays at the lock can sometimes create waits of up to 12 hours as tug crews wait to take their tows through – a process that can take as long as four hours on its own.

The Kentucky Lock Addition Project – a more than $1.5 billion federal construction effort led by government contractors, including Thalle Construction, and U.S. Army Corps of Engineers (USACE) workers – aims to solve the logjam by doubling the length of the lock that flows resources and products to 20 states.

Jeremiah Manning, the senior resident engineer with USACE for the project site in Grand Rivers, said that the current delays faced at the lock are the greatest in the USACE system. He expects that to change when this project is complete.

“When we go to a 1,200-foot chamber, the efficiency that’s born into that and the way that they typically arrive at the site will take that queue to virtually nothing,” Manning said.

Capt. Rachel Nelson manages the Kentucky Lock Addition Project for the U.S. Army Corps of Engineers. She believes the project will make a major economic difference by shortening transit times for goods shipped on the river in the region, with projections for the annual economic benefit from the larger lock estimated at around $114.3 million.

“Everything that will travel through this lock, hopefully, not only will bring goods to people but also, because of the delay decreases, it will make goods cheaper for people,” she said. “This project truly is for the American people and to kind of help drive industry in and across the inland navigation waterways.”

Ground broke on the project 25 years ago, and construction hit a milestone last month with the completion of the first of its downstream monoliths. These monoliths, built out of five-foot concrete layers, called lifts, form the core of the lock’s structure. Construction workers have been pouring lifts for the lock for over a decade, finishing the first of the upstream monoliths in 2015.

Nelson said the expanded lock is being built piece-by-piece in a way to provide it with structural integrity “for 100 years to come.”

“You can’t just put all of this concrete in at one time. We have to do it in five foot lifts. And that’s kind of part why it is such a complex project,” she said. “There’s not a Lego that’s 17 Legos deep, you have to put 17 Legos together to build a tower.”

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Capt. Rachel Nelson with the U.S. Army Corps of Engineers demonstrates the difference in capacity between the original 600-foot Kentucky Lock and the 1,200-foot one being constructed alongside it as part of the Kentucky Lock Addition Project.

The 600-foot original lock, completed in 1942, is only capable of handling portions of what’s become the industry-standard tow along U.S. waterways. Most river transport companies send tugboats out with 15-barge tows, arranged in a three-by-five grid to carry the equivalent of more than 1,000 semis worth of goods.

These tows must be broken up into two smaller grids to get through Kentucky Lock. This process, Nelson said, can be time-consuming and potentially dangerous for tug crews.

The original lock will be left in place alongside the new, 1,200-foot lock to operate as an auxiliary lock that can accommodate recreational vessels and smaller tow loads and create a redundancy.

This dual-length setup is expected to greatly increase the lock’s capacity, practically eliminating the bottlenecking of traffic at that point in the inland waterway. Manning said it also frees up more water to generate hydroelectric power at Kentucky Dam, operated by the Tennessee Valley Authority. It also eliminates the potential hazards of crews needing to separate their tows to navigate the lock, he added.

“Since we’re not doing that – that double iteration where the longshoremen are down there on the boats tearing that apart and then reconnecting it – we’re avoiding a major safety hazard to the industry,” Manning added.

The construction effort over the past couple of decades has been massive. Separate stints of the project have involved relocating portions of the state highway and logistically rerouting railroads, powerlines and other utilities at the site. The amount of concrete poured at the site since just 2022 is monumental.

“We’re sitting at about 140,000 cubic yards right now and growing,” Nelson said. “For this contract alone, we’ll be placing about 375,000 cubic yards of concrete, which is equivalent to about six Empire State Buildings.”

Manning said the scale of the effort is worth it because of the difference it could make for the U.S. economy and for companies operating on the waterways.

“The quicker that industry can move through the lock, and that means the quicker they’re on their way, and enhances their ability to make a profit margin,” he said. “The value that we will deliver when we go operational is substantial to the industry, which then will translate into lower costs to ship goods, which should ultimately get to the customer.”

Nearby Barkley Lock allows access to the Cumberland River, which Nelson calls “a two-lane state highway” compared to “an interstate” in the Tennessee.

“So when you’re thinking about a 15-tow barge going through that, it’s very time consuming and it’s very dangerous [as opposed to] when you look at the Tennessee River,” she said. “So typically, industry does prefer to travel down the Tennessee River.”

Barkley Lock and Kentucky Lock collectively flow around 57 million tons of product each year. That includes products like coal, soybeans, corn and construction materials such as sand, gravel, limestone and iron. According to the U.S. Army Corps of Engineers, those products combine to create about $10 billion in economic stimulus annually.

Many of the region’s locks and dams were built by the U.S. Army Corps of Engineers in the decades leading up to World War II and were originally designed to last up to 75 years. According to the American Society of Civil Engineers, most of the more than 200 locks on USACE waterways are “well past their 50-year design life.”

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A worker checks examines his progress atop one of the concrete monoliths at the Kentucky Lock Addition Project in Grand Rivers.

The original lock was built in just seven years and the goalposts on the new one have moved a couple of times since its inception in the mid-1990s. The project didn’t receive substantial funding until 2015 and Nelson said not getting consistent funding has been a big factor in the project’s timeline.

The Waterways Council has advocated for a modern national system of inland waterways and ports for decades. Deb Calhoun, senior vice president with the group, said it’s vital to the U.S. economy to expand and renovate aging infrastructure like Kentucky Lock, as well as others across the country.

“We see these locks and dams that have been built on the inland waterway system in the 1920s – some of them were built in the 1910s – and certainly they have outlived their 50-year economic life, if you will,” she said. “So it’s time to recapitalize this part of the transportation infrastructure network.”

Calhoun believes solving “the longest shipping delays in the country” will be a big boon for the industry.

“[It] will be a tremendous efficiency gained for shippers and certainly for receivers of those important commodities, whether it’s an energy product or an ag product or an aggregate material that is used for the construction industry, or whatever it may be,” Calhoun said. “When these locks were first created, they were built very quickly on the system really during the New Deal of the Roosevelt administration and here we are in sort of the New Deal 2 or 3.0, if you will.”

The current contract is expected to be completed in 2027, with the next steps including approach walls and utilities for the new lock at Grand Rivers. The project as a whole is projected to finish in 2029.