TVA hits ‘grand slam’ with first Tier 4 line-haul towboat

Freedom is Tennessee Valley Authority’s first new line-haul towboat in almost 40 years. It is based in Muscle Shoals, Ala., but has covered a lot of territory along other U.S. inland waterways.
Freedom is Tennessee Valley Authority’s first new line-haul towboat in almost 40 years. It is based in Muscle Shoals, Ala., but has covered a lot of territory along other U.S. inland waterways.


Freedom
|Tennessee Valley Authority, Muscle Shoals, Ala.

Almost four years ago, during the early days of the Covid-19 pandemic, the Tennessee Valley Authority (TVA) began developing its first new towboat in almost 40 years.

The government-owned electric utility based in Knoxville, Tenn., didn’t need 10 new boats or even three. It just needed one. And that one towboat had to perform right away and last a generation or two. No pressure, right?

“The TVA is not in the business of building boats,” admitted Shane Carman, a 25-year riverboat pilot and river services manager for the TVA. “We knew we had to hit a grand slam the first time. We couldn’t afford to have things go wrong or say later, ‘We should have done this totally differently.’ We had to really think about what we were doing.”

Ultimately, the TVA hit all the right marks with Freedom, a 100-by-34-foot towboat designed by Sterling Marine and built by Vessel Repair Inc. The 2,682-hp tugboat is powered by EPA-rated Tier 4 Caterpillar main engines, making it the first Tier 4 towing vessel to enter service for a government agency, according to the TVA.

Crew comfort was a key focus on Freedom, which has five cabins — each with an attached private head — and nine bathrooms in all. Interior spaces are finished with wood, and crewmembers have access to wireless internet and satellite TV. Extra attention went into reducing vibration and engine noise throughout the vessel.

“Whenever I set foot on this boat, I am thinking, ‘Man, I might have picked the wrong career,’” said David Carver, a naval architect with Sterling Marine who helped design the vessel. “I could live on this thing for two weeks at a time.”

The TVA dates to the New Deal era of the 1930s, when its electrical projects ushered in a wave of prosperity across the Tennessee Valley. Early TVA hydroelectric powerplants controlled floodwaters on the Tennessee River and generated cheap electrical power that attracted factories, mills and other employers to a region with limited economic activity.

These days, the TVA remains a private corporation owned by the federal government. It is the nation’s third largest power generator and the largest public power provider. Its portfolio includes 29 hydropower facilities, nearly two dozen coal and gas powerplants, three nuclear plants and a growing portfolio of renewable energy sites.

The TVA’s small fleet of towboats and barges help keep these plants running. Freedom, which is based in Muscle Shoals, Ala., often pushes a single 160-foot barge loaded with highly specialized and incredibly expensive generating equipment. Since entering service in summer 2023, Freedom has run on the Tennessee-Tombigbee Waterway and the Tennessee and Cumberland rivers.

Freedom typically tows a barge loaded with components for TVA powerplants throughout Tennessee and the Mid-South.
Freedom typically tows a barge loaded with components for TVA powerplants throughout Tennessee and the Mid-South.

Although it’s not designed for speed, Freedom has pushed a loaded barge beyond 13 mph in slack water with power to spare. Despite its size, the towboat is nimble and highly responsive, giving operators confidence to operate in tight quarters and sensitive areas, such as against a dam wall.

“You’d think the bigger you go, you’re going to be big and lanky, but that is not the case with this boat,” Carman said. “It is very maneuverable, very agile and quick in response. It is impressive how you can make the boat react very, very quickly.

“The rudders are very fast, very responsive and you can make the boat do anything you want it to do,” he continued.

Freedom is based on a proven hull form Sterling Marine fine-tuned over the years for optimal efficiency. Carver said it has a large main rudder profile area and flanking rudders positioned as close to the propellers as possible without affecting water flow.

Pilot Jesse Rogers at the helm in Freedom’s well-adorned wheelhouse. The TVA takes great pride in the vessel’s outfitting and crew comforts.
Pilot Jesse Rogers at the helm in Freedom’s well-adorned wheelhouse. The TVA takes great pride in the vessel’s outfitting and crew comforts.

The 100-by-34-foot package, however, changed dramatically during the design phase. The TVA initially considered building a triple-screw towboat with Tier 3 engines in the 90-foot range. It spent nearly a year working with Sterling Marine to zero in on the right size and propulsion platform. Crew comfort and reduced environmental footprint were top priorities for the vessel. Achieving those goals meant building a longer, wider boat, which in turn meant installing more powerful Tier 4 engines.

Cleaner-burning Tier 4 engines have been standard on ship-assist tugboats for the better part of a decade, but inland operators have been slow to embrace the technology for multiple reasons. The presence of a selective catalytic reduction (SCR) system on Tier 4 powerplants is the primary difference between the two platforms. These require diesel exhaust fluid that must be stored on board and acquired regularly, typically when taking fuel.

Carman, who began his career as a deck hand with Cooper Marine, approached the company to learn more about Gretchen V. Cooper. That towboat, built in 2021, was the first Tier 4 towboat working on the inland waterways. TVA officials toured the vessel and learned more about its Tier 4 propulsion system. Some lessons drawn from that vessel incorporated the design and outfitting on Freedom, Carman said.

Freedom is powered by two Caterpillar 3512E main engines each producing about 1,340 hp that turn 85-inch Sound propellers through Twin Disc reduction gears. Electrical power comes from two Cat C4.4 generators sparking 99 kW of power for hotel loads, navigation electronics and deck equipment. 

Freedom represented the first Tier 4 propulsion project for Sterling Marine and Vessel Repair. Carver initially designed the towboat to accommodate the Caterpillar mains in the lower engine room and the SCR units in the upper engine space. Crews at Vessel Repair recognized potential issues with that configuration during construction.

Kurt Moerbe, a Vessel Repair vice president, said space was tight to accommodate the SCR units — a concern long expressed by operators and naval architects. The shipyard also thought excess heat from the SCR system would creep into adjacent crew spaces. Discussions ensued among the TVA, the shipyard and Carver to identify a solution.

Carver found components necessary to install each SCR unit vertically in each respective stack and modified his design accordingly. The new configuration freed space in the engine room and would allow heat from the SCR units to escape via the stack openings. Sterling Marine and Vessel Repair have since adapted this innovation to other Tier 4 towboat projects. 

“It takes someone getting in there and getting dirty,” Carver said of the design change. “We can look at this stuff on paper all day. … It just takes one person asking the question, and then the process turns toward finding a solution. And that is where we ended up here.”

Thompson Tractor, the Caterpillar dealer based near Mobile, Ala., that supplied the engines and gensets, also provided invaluable support with the Tier 4 propulsion system, according to Carver and Moerbe.

Over the years, Vessel Repair has primarily focused on commercial customers. As such, the yard had some early reluctance to pursue the project with the TVA, which was among its first government customers.

But at the time, with the Covid-19 pandemic still raging, there weren’t a ton of other projects available. 

Ultimately, the project proved a success. Moerbe said the TVA was a pleasure to work with, and he praised the flexibility of Sterling Marine. Vessel Repair and the TVA have continued their relationship, with multiple barges under construction for the agency.

“We were fortunate to get a few of these (Tier 4) projects on the front end,” Moerbe said. “We are bidding boats currently for other customers and one of the questions they are asking is, ‘Have you dealt with Tier 4?’ So, we got to notch our belt pretty quick in this phase.”

Freedom has started to garner attention across the broader inland towing community. Carman is now fielding inquiries from operators who have heard about it and want to see it for themselves. That type of affirmation has become a point of pride for the TVA and the sign of a vessel designed and built right.

“How did we do with the boat? We did hit a grand slam,” Carman said. “We not only hit it out of the park, we hit it into the river outside the park.”