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First Concrete Monolith of Tennessee River Navigation Lock Completed

Posted on May 25, 2023

CHATTANOOGA, Tenn. (May 23, 2023) – Construction of a new navigation lock on the Tennessee River reached a monolithic milestone yesterday as crews and officials held a topping-off ceremony to mark the completion of the first concrete monolith.

Officials and employees from the U.S. Army Corps of Engineers Nashville District and its contractor, Shimmick, assembled near the construction site to celebrate the occasion and highlight partnering efforts as construction of the lock chamber progresses.

Shimmick Chief Executive Officer and President Steve Richards gave the signal and Crane Operator Patrick Harrison lifted the last concrete form from monolith L13 to mark the official completion of the first of 36 monoliths. Crews placed more than 4,000 cubic yards of concrete into the 87-foot monolith, which is enough concrete to construct the foundations of approximately 150 homes.

Lt. Col. Joseph Sahl, Nashville District commander, thanked and congratulated the USACE construction team and the contractor for achieving this great milestone and for having the commitment to work through challenges without sacrificing safety or quality.

“As the project encountered challenges, I have been impressed by this team,” Sahl said. “We’re here today because you all dedicate yourselves daily to safely delivering this quality project.”

In addressing the Shimmick team, Sahl noted the continued commitment to quality and lauded the efforts of their on-site workers and engineering team.

“Their ability to proactively engage our engineering and construction teams has helped identify many issues early and we appreciate the approach they have taken to being a partner with us in this project,” Sahl said.

Richards said the completion of L13 is the culmination of two years of hard work by the 450 craft workers that Shimmick employees, which has overcome lots of challenges.

He noted that Shimmick and legacy companies have been involved with building landmark projects like Hoover Dam, Dale Hollow Dam, Olmstead Dam, and the Tennessee-Tombigbee Waterway.

“Simply put, Shimmick builds America’s infrastructure,” Richards said.

With the Chickamauga Lock Replacement Project, Shimmick has spent $112 million on payroll to date, $12 million on contracts with local small businesses, and $17 million on contracts with local large businesses. The contracts include five veteran-owned businesses, seven women-owned small businesses, four disadvantaged-owned businesses, and two historically underutilized business zone companies.

Delivering a project that will last for generations is only accomplished with close partnerships, Sahl added, which includes close interaction with Shimmick and with the Tennessee Valley Authority, which is a close federal partner that is involved with ensuring the new navigation lock is integrated safely into the current dam structure.

The base dimensions of the L13 monolith is 51-feet long by 31.5-feet wide at the base. At the top it is 20-feet wide and 51-feet long. The Corps of Engineers is nearly two thirds of the way complete with concrete placement for the lock chamber and is approaching the halfway point for all contracts associated with the project.

The new lock chamber is expected to be completed in the fall of 2026, and the majority of the site work to be completed by the end of 2028.

In looking forward to the completion of the lock chamber, Tennessee District 3 Rep. Chuck Fleischmann provided a statement for the ceremony congratulating Shimmick, and reinforcing his commitment to the U.S. Army Corps of Engineers in the development of infrastructure in the 3rd District.

TVA completed construction of Chickamauga Lock and Dam in 1940. The lock has since experienced structural problems resulting from alkali aggregate reaction between the alkali in the cement and the rock aggregate, which results in a physical expansion of concrete structures. Even with costly advanced maintenance procedures, the concrete expansion threatens the structural integrity of the lock and limits its life span.

With significant annual maintenance, Chickamauga Lock has frequent and lengthy lock outages as a result of downtime for repairs. Up to now, Corps maintenance crews have kept the lock open as the concrete continues to expand and hinder operations.

Chickamauga Lock remains one of the most important current construction projects in the Corps of Engineers because it is so critical to the economy, commerce, and recreation in East Tennessee. It passes approximately one million tons of commodities annually and is the most active lock on the Tennessee River for recreational vessels. If the current lock were to close prior to completion of the replacement lock, the direct impact would be closure of 318 miles of river and associated movement of traffic upstream of Chattanooga.

The active navigation lock is 360-feet long and 60-feet wide and only fits one barge. When constructed, the new lock will be 600-feet long and 110-feet wide, and will handle nine barges per lockage. It will reduce commercial transit times by 80%.

The project to construct the lock chamber is cost shared between the federal government and with navigation industry through the Inland Waterway Trust Fund, which generates its revenues from a 29-cents tax on marine diesel fuel.

(For more news, updates and information please follow the Nashville District on Facebook at and Twitter at The public can also follow Chickamauga Lock on Facebook at


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