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Monolithic effort to construct lock chamber heats up

Nashville District Public Affairs
Published July 23, 2020
A Shimmick construction worker installs reinforcing steel July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

A Shimmick construction worker installs reinforcing steel July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

U.S. Army Corps of Engineers and Shimmick construction crews work to construct monoliths July 21, 2020 for a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project. (USACE Photo by Lee Roberts)

U.S. Army Corps of Engineers and Shimmick construction crews work to construct monoliths July 21, 2020 for a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project. (USACE Photo by Lee Roberts)

U.S. Army Corps of Engineers and Shimmick construction crews work to construct monoliths July 21, 2020 for a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project. (USACE Photo by Lee Roberts)

U.S. Army Corps of Engineers and Shimmick construction crews work to construct monoliths July 21, 2020 for a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project. (USACE Photo by Lee Roberts)

Shimmick construction workers prepare the riverbed inside a coffer dam July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

Shimmick construction workers prepare the riverbed inside a coffer dam July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

A Shimmick construction worker prepares steel forms July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

A Shimmick construction worker prepares steel forms July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

Corps construction representatives oversee Shimmick contractors preparing to drill holes July 21, 2020 to install reinforcing steel in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

Corps construction representatives oversee Shimmick contractors preparing to drill holes July 21, 2020 to install reinforcing steel in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

A Shimmick construction worker installs reinforcing steel July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

A Shimmick construction worker installs reinforcing steel July 21, 2020 in preparation to place more concrete for a monolith. The U.S. Army Corps of Engineers Nashville District is constructing a new navigation lock as part of the Chickamauga Lock Replacement Project at the Tennessee Valley Authority project on the Tennessee River in Chattanooga, Tennessee. (USACE Photo by Lee Roberts)

CHATTANOOGA, Tenn. (July 23, 2020) – A monolithic effort to construct a navigation chamber at the Chickamauga Lock Replacement Project is heating up where the U.S. Army Corps of Engineers Nashville District has already placed 19,000 cubic yards of concrete and more than 700 tons of reinforcing steel.

With temps in the high 90s, Tommy Long, Nashville District resident engineer, said work crews are mainly concentrating on preparing forms and installing reinforcing steel while the contractor makes adjustments at the batch plant to cool the concrete mixture within specifications as ambient temperatures make it difficult to keep it under 70 degrees.

“The contractor is looking at adding ice to the concrete mixes, and would likely place concrete during nighttime hours when temperatures are significantly reduced,” Long said. “The project is moving forward with foundation preparations, form work and installation of rebar.”

So far the contractor has placed concrete in 33 monolith areas that combine to make up the new lock chamber structure. In addition, foundation cleanup continues in areas still exposed and drilling for anchors into the existing segmental wall is underway. The formwork is in place around the entire lock chamber footprint, giving a visual representation of where concrete is being placed.

Bill Groth, Shimmick project manager, said construction crews are embedding special fabricated supports and anchors to prevent movement of embedded steel liners and guides during concrete placement.

“Engineering of formwork, block outs and reinforcing steel for the upper lifts continue,” Groth said. “All 43 drilled shafts are complete.”

The monolithic effort to construct the new navigation lock chamber is moving forward even as the Corps of Engineers and Shimmick pay close attention to health and safety on the work site to safeguard employees during the COVID-19 pandemic. Construction has continued throughout the pandemic since the project is supporting critical navigation infrastructure improvements.

Groth praised his team for overcoming the challenges, especially those associated with COVID-19.

“They continue to show up to work every day to construct the project despite the fears of contracting the virus and exposing their family members,” Groth said. “I am very proud of the effort and dedication the employees, both craft and staff, are giving to come to work every day to construct this project! Without them working as a team, the project would stall.”

Kyle Phillips, civil engineer at the Chickamauga Lock Resident Engineer Office, said construction workers are wearing masks, a difficult task in the extreme heat, so they are taking frequent breaks to catch their breath and drinking plenty of water to stay hydrated.  Safety is a priority for the Corps of Engineers, and it is exciting to see the hard work paying off as the lock chamber begins to take shape, he noted.

“It’s a really good feeling to get up and off the ground,” Phillips said. “It’s almost to that point now where you can almost visualize the lock being vertical.”

Chickamauga Lock, seven miles upstream of Chattanooga, Tennessee, at river mile 471, is owned by the Tennessee Valley Authority and operated by the U.S. Army Corps of Engineers. A concrete aggregate problem causes structural concerns at the existing lock and will result in closure of the lock at some point. 

The existing 60-foot by 360-foot lock is a non-standard size that is not suited to the barges used by the transportation industry today. The new 110-foot by 600-foot Chickamauga Lock will replace the existing lock, and improve locking efficiency.

Adam Walker, Nashville District project manager, explained that the Corps of Engineers awarded the base of the lock chamber contract in September 2017 and contract options have been added each subsequent fiscal year as funds became available.

Walker said as of June 15, 2020 all options have been exercised, which brings the contract value to approximately $244.7 million, and extended the contract required completion date to July 1, 2023. The total project cost estimate is currently at $756.9 million at fiscal year 2020 price levels, assuming a November 2025 completion date, he added.

The approach walls and decommissioning contract will follow the lock chamber contract. The Nashville District anticipates awarding this contract in September 2021, which will include breaching Chickamauga Dam and removing the cofferdam structure.

“The final planned contract for the project is the site restoration construction that is anticipated for award in September 2024,” Walker said. “The new lock is anticipated to be operational around November 2023.”

(The public can obtain news, updates and information from the U.S. Army Corps of Engineers Nashville District on the district’s website at www.lrn.usace.army.mil, on Facebook at http://www.facebook.com/nashvillecorps and on Twitter at http://www.twitter.com/nashvillecorps.)