Photo above: The U.S. Army Corps of Engineers Nashville District constructs a new navigation lock February 20, 2024. The dam is a Tennessee Valley Authority project. The Nashville District is managing the Chickamauga Lock Replacement Project. USACE photo by Luciano Vera.

This original article was published in the May/June 2025 Issue of Wire Rope Exchange

BY: Bob Glenn, Editor and Publisher

The Nashville District of the U.S. Army Corps of Engineers (USACE) is presently engaged in a years-long project to replace the existing Chickamauga Lock with a vastly expanded and improved facility. The replacement project began in 2004, with a total cost approaching $1 Billion and an expected completion date February 2031. The lock allows vessels to transit the Chickamauga Dam, a Tennessee Valley Authority (TVA) project located at Tennessee River Mile 471, a few miles upstream to the northeast of downtown Chattanooga, TN.

Navigation on the Tennessee River

The Tennessee River has been a critical transportation artery for the Tennessee Valley throughout its history, presenting a variety of hazards for early navigators – Native Americans and settlers alike – ranging from floods and droughts to swift currents and rocky shoals. The shoals survive the TVA’s efforts in legacy. Muscle Shoals, namesake of the musically famous region and town, originally referred to a portion of river that falls 84 feet in 14.5 miles, accounting for a major part of the “Muscle Shoals Section” of the river, where low water elevation loses 134 feet in 36.6 miles as described by Major Harry Burgess, Corps of Engineers, in his 1914 report “Muscle Shoals Section, Tennessee River, Alabama; Combined Navigation Improvement and Power Development.” For more details and a fascinating look at early infrastructure, as well as discussion of the unique underlying geology of the region, visit https://www.jstor.org/stable/44709463

As the title of his report suggests, the TVA, later established in 1933, was not only intended to provide flood control and hydroelectric power, but also to support dramatic improvements in navigation, making the river a reliable, major source of transportation for the region. The modern navigation channel supported by a system of dams and locks and extending 652 miles, was largely complete by 1945. Beginning where the Tennessee flows into the Ohio River near Paducah, KY, the channel extends to just above Knoxville, TN, and connects to 112 more navigable miles in three tributaries.

Today, about 50 million tons of cargo transits the system annually, hauled by about 28,000 barges. According to the TVA, the benefit of transporting bulk cargo by barge on the system rather than truck or rail cuts annual costs by $400 million.

Concrete Growth

Shortly after completion of the Chickamauga Dam and Lock in 1940, a phenomenon of concrete expansion was observed. While concrete structures are generally built to accommodate concrete shrinkage over time, in this instance and two other major TVA projects, alkali-silicate or alkali-carbonate reactions between the cement and concrete aggregate cause progressive expansion over time. Despite monitoring and remediation efforts, this phenomenon ultimately constrains the service life of the project.

Scale of the Replacement Lock

318 miles of navigation channel, or about 40% of the length of the Tennessee River navigation system, lie upstream of the Chickamauga lock. Major users above the lock include the Department of Energy at Oak Ridge, TN, the TVA itself, and numerous other businesses including a notable cluster of boat manufacturers. A study from the University of Tennessee Center for Transportation Research published in 2015 documented 959,290 tons of commodity cargo transited the lock in 2013, and that excludes boats, ships, caissons and barge mounted cranes as those are not counted as commodities.

When complete, the current 60-foot by 360-foot lock will be replaced by a 110-foot by 600-foot facility located below the dam and toward the river’s center from the existing lock. While total square footage expands by a factor of 3, the new dimensions are closely in line with the common “Jumbo” barge, which is 195-200 feet in length and 35 feet wide, enabling the new facility to handle nine per cycle rather than only one.

Major Milestones

Spending on the project through December 2024 totaled roughly $569 Million. Work begun in 2004 and running through 2012 included relocation of highways and utilities, construction of the cofferdam, and manufacture of numerous lock components including culvert bulkheads and miter gates stored by the TVA until needed. Funding of the project was suspended following that work until FY2015 due to constraints in allocation from the Inland Waterways Trust Fund (IWTF), which derives revenue from taxes on diesel fuel used by tow vessels and is intended to fund one-third of costs for major rehabilitation and construction on inland waterways.

As of June 2024, the risk-based total cost estimate for the project stood at 954.4 Million at FY2023 prices. Several major contracts remain to be completed or awarded.

In 2017 a $309 Million contact was awarded for the Lock Chamber which completes the new lock facility inside the previously constructed cofferdam. That work is projected to conclude in 2026, with miter gate installation presently underway and continuing through 2025.

In 2021, a $68 Million contract for the Upstream Approach Wall was awarded. This installation protects vessels entering the lock above the dam from current generated by water being diverted to the dam’s spillway, and enhances efficiency of the lock with a tow haulage system which assists with positioning tows through the lock chamber using a cable and hoist mechanism.

A contract has yet to be awarded for the Approach Wall and Decommissioning. That is expected to be awarded later this year to be in service in early 2028.

Lifting Equipment

This project entails a broad range of material handling and heavy lifting activities, relying on an impressive fleet of cranes on site. Work on the lock chamber has utilized numerous cranes including a Manitowoc 300-ton MLC300 S3 Crawler Crane, a Manitowoc 275-ton 999 Crawler Crane, two Terex CTT721-40 Tower Cranes, and a Liebherr 1800C60 Hammerhead Tower Crane. There have also been multiple rough-terrain cranes on site (Grove 40-ton, Tadano 75-ton, Link-Belt 100 RT, Liebherr 110-2.1, etc.) along with mini crawler cranes for more confined or specialized operations through the course of the project.

In addition to that equipment, work on the upstream approach wall has relied on multiple 300-ton and 230-ton crawlers including Manitowoc model 2250, 4100 and 777 cranes.

Lifting Operations

A number of critical aspects of the project have required significant lifting operations with more planned to complete the project.

Perhaps the most significant of these currently underway involves miter gate installation. Work to assemble and install the miter gates for each end of the new lock began with delivery of the 14 gates leaf panels to the jobsite in December 2024. Each leaf panel weighs between 150,000 and 190,000 pounds. When complete, each of the two downstream gates will consist of five leaf panels and stand 71 feet tall and 62 feet wide while the two upstream gates, 30 feet tall and 62 feet wide, will each be built from two leaf panels.

The leaf panels were fabricated in Birmingham, AL and shipped by barge to a staging site before delivery to the jobsite. The gates are coated with anti-corrosion material to minimize maintenance requirements and extend their service life. At the site, they were lifted into the cofferdam by a Manitowoc 999 and MLC300. Installation of the gates began this April, with pieces being moved into place using the MLC300 to lift and position each piece to be welded together onsite. That work will continue through December 2025.

“Seeing these massive gate pieces lifted and assembled into place is truly a testament to the expertise and coordination required in mega infrastructure projects. This process marks a significant achievement in the progress of the Chickamauga Lock Replacement Project and brings us closer to project operational status,” said Kyle Phillips, technical lead for the U.S. Army Corps of Engineers Nashville District, as quoted in a recent press release from the District.

Another milestone was reached in April of this year with delivery of the second Nose Pier Shell. The 29.5 foot tall steel structure was transported up the Tennessee river by barge, passing through four other locks on its way from Luka, Mississippi.

The nose pier extends from the head of the approach wall, protecting the approach wall. Rather than being pre-cast, the shell is filled with concrete after it is vertically placed and fully installed.

Delivery of the approach wall beams will be a major next step. Those 10-foot by 10-foot beams are currently stored at Watts Bar (another TVA facility) and will be transported to the site by barge in August 2025. Some measure as much as 120 feet in length and weigh up to 420 tons. Transporting these will be a complex logistical operation, and their installation will require precision alignment and complex rigging as that operation will take place near live river traffic.

Other major lift operations to be completed will include placement of Precast Approach Wall Beams. The approach wall will incorporate 42 massive 10-foot by 10-foot beams. There will be three segments of these beams, with each up to 120 feet long and weighing up to 420 tons. This will require precision alignment and complex rigging as this work takes place near live river traffic.

Four culvert valves measuring 18 feet by 12 feet, and weighing 47,000 pounds also remain to be placed. Additionally, a steel crossover bridge spanning 112 feet and a lock wall access bridge spanning 28 feet remain to be moved into place.

Wrapping Up

In response to Wire Rope Exchange, a representative from the USACE Nashville District wrote that “these lifts require strict coordination, structural precision, and often occur in confined spaces with active construction or water nearby — all of which increase complexity and demand expert rigging strategies.”

We specifically asked the management team to describe the significance of lifting operations for the completion of this project. “The scale and precision of the lifting operations at Chickamauga Lock reflect the critical role that rigging and lifting professionals play in making these mega-infrastructure projects possible,” said Chickamauga Lock Project Manager Bob Winters. “Every beam, valve, and gate leaf moved here supports the future of commercial navigation on the Tennessee River and the regional economy it powers.”