Nearly four years after it ran out of money, the Army Corps of Engineers resumed work this week on the Chickamauga Navigation Lock on the Tennessee River with a $3 million contract for renewing cofferdam work around the new lock.

It is a small payment toward a project anticipated to cost $600 million if it were fully funded – still an iffy proposition, given the Corps’ tight funding for inland projects.

The Obama administration’s Office of Management and Budget had scratched Chickamauga from the Corps budget for 2017, with cost-benefit analysis that placed it as a lower priority. The administration recommended funding for only the Olmsted Lock and Dam project on the Ohio River in Illinois.

The Chickamauga lock near Chattanooga allows navigation on 318 miles of the upper river, and the existing 76-year-old structure is beset with failing concrete aggregate that requires “aggressive maintenance,” according to the Corps’ Nashville district engineers.

A failure at the old lock would spell big trouble for commerce, says Cline Jones, executive director of the Tennessee River Valley Association. Already corn shippers have been avoiding Chickamauga to avoid delays from breakdowns and maintenance.

“The procedural liability has chased a lot of traffic away,” Jones said. Chemicals and other cargoes still transit the lock, but Chickamauga's one million annual tons puts it at a disadvantage with competing project that may serve 10 times as much cargo, Jones said.

“The cost has gone up, while the traffic has gone down,” he said. Still, there are some 3,500 lockings a year, and behind the dam Lake Chickamauga is a major recreational draw for the Chattanooga region.

While the Corps deals with crumbling infrastructure across the inland waterways, geology and chemistry combine to make Chickamauga’s unique problem: a lock that has grown out of whack, mutated by mineral buildup on the concrete that misaligns gates and valves.

“When the TVA [Tennessee Valley Authority] built these projects they used local materials,” Jones said. “Around Chattanooga, they found a local aggregate that turned out to be marginal. Each little pebble reacts with the river water.”

“The story goes that since 1940 the lock has grown 4” in height and 12’ in length,” he said. Over the years Corps engineers have drilled, bolted and tied the structure to keep it in alignment.

“At some point the risk will be so high the TVA will be forced to close the lock and we’ll lose 318 miles of river,” including barge transport to two nuclear power plants, Jones said.

04.26.16 ChickLock illustrationA USACE illustration shows plans for the Chickamauga Lock.The existing 60’x360’ lock is tiny and archaic by modern barge industry standards, and the design includes a 110’x600’ lock to accommodate modern tows. Construction began with roadway relocations in 2007 and the design was completed in 2009.

The cofferdam was completed in 2012, as were the miter gates, culvert valves and culvert bulkheads that are now in storage at a Tennessee Valley Authority facility at Muscle Shoals, Ala.

Shortly after, funding from the Inland Waterways Trust Fund ran out. The Corps was able to use $3.1 million in surplus from last year to resume the cofferdam work, and Tennessee’s Congressional delegation including Rep. Chuck Fleischmann and Sen. Lamar Alexander, both R-Tenn., helped obtain new funding of $29.9 million.

“The best case scenario is the lock could be operational in 2023 or 2024,” Jones said. “We’re going to be fighting this for years to come…But we’ve got $280 million invested, so we should be saying, “Let’s get this done, so we can move on.”