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Chickamauga Lock Replacement Project

Construction

Nashville District
Published June 20, 2024
Construction work being completed at Chickamauga Lock.

The U.S. Army Corps of Engineers Nashville District constructs a new navigation lock Feb. 20, 2024. The dam is a Tennessee Valley Authority project. The Nashville District is managing the Chickamauga Lock Replacement Project.

LOCATION

Tennessee River Mile 471 in Chattanooga, Tennessee

PROJECT DESCRIPTION AND BACKGROUND

The replacement lock project consists of a new 110’x 600’ lock to be located riverward of the existing 60’x 360’ lock and downstream of Chickamauga Dam. A new lock is required at Chickamauga Dam because of structural deficiencies of the existing lock resulting from physical expansion of the concrete structure.  This phenomenon of concrete growth was observed soon after initial construction in 1940 and is caused by a reaction between the alkali in the cement and the aggregate.  Even with significant maintenance efforts, this expansion threatens the structural integrity of the existing lock and limits its life.

Replacement lock construction began in 2004 with highway and utility relocations and continued through 2012 with the completion of the cofferdam structure and prefabricated components (miter gates, culvert valves, culvert bulkheads, and approach wall beams) that are currently being stored at other Tennessee Valley Authority (TVA) facilities until needed.  After a temporary suspension of construction activities due to funding constraints with the Inland Waterways Trust Fund (IWTF), funding returned to the project in FY15.  Like all locks on the Tennessee River, the existing and proposed locks are owned by the TVA but operated and maintained by the Corps of Engineers.

The new lock is vital to maintain 318 miles of navigable channels upstream of Chickamauga Lock and Dam to support stakeholders including the Department of Energy at Oak Ridge, TN, TVA, and numerous other businesses.

CURRENT STATUS

Chickamauga Lock’s current risk based total project cost estimate is $954.4M (FY23 price level); approximately $417M has been expended through April 2023. Estimated project completion between September 2028 and August 2030, but that is subject to change due to delays with contracts and how remaining costs are funded. The 2023 TPCE indicates an additional $236.8M is required for project completion.

The $257M Lock Chamber contract was awarded on 28 September 2017; it is currently 58% complete based on payments. The current LC required contract completion date is 10 November 2023, but that date will not be achieved due to slower than anticipated concrete placement rates. The LC contract will result in a completed navigational lock located inside the cofferdam.

The new lock will open to traffic after the dam and cofferdam structures are breached, which will occur after the $61M Upstream Approach Wall (USAW) contract (awarded 9 September 2021 with a required completion date of 13 March 2024) and during the follow-on Approach Walls and Decommissioning (AWD) contract. 

The award of the AWD contract is planned for September 2024 with a in service date of November 2026.

The project’s total Benefit to Cost Ratio (BCR) at a 7% discount rate is 1.0 and its Remaining Benefit to Remaining Cost Ratio is 1.5.  At the FY18 discount rate of 2.75%, these Ratios increase to 1.7 and 2.6, respectively. A reassessment of the economics supporting this project is expected to be complete in May 2024.

AUTHORIZATION 

Consolidated Appropriations Act of 2003 (P.L. 108-7); reauthorized in America’s Water Infrastructure Act of 2018 (P.L. 115-270)