"These are the oldest and smallest [locks and dams] on the Ohio here," said Chris Dening, project manager, for the Corps Pittsburgh District. "When I say smallest, that means everything downstream here is twice as big. They have a 1,200-ft capacity. This only has a 600-ft one, so it becomes kind of a natural bottleneck for industry when they're coming up toward the Port of Pittsburgh ... they're coming up on 100 years old at this point. They've seen a lot of wear and tear. They were rehabbed in the 80s, and that was to extend their life another 25 years. So if you do the math on that, you know we're in overtime."

Maintenance activities on the small locks can cause navigational bottlenecks on the Ohio and if the locks were closed to perform such work, according to the Waterways Council, a Washington, D.C.-based lobbying group representing users of the nation's inland waterways. The economic impact of just a one-year closure at Montgomery Locks and Dam would cost the U.S. economy nearly $180 million, the council said.

Jenna Cunningham, resident engineer for the Corps' Pittsburgh District, said the project is still in single digits of completion as a percentage of the entire work and it will continue to be built in the wet until the engineering command is satisfied that a cofferdam can be built for the final phases of construction to be completed in the dry.

Army Corps Resident Engineer Jenna Cunningham explains the construction plan at the $1.59-billion Montgomery Lock and Dam project in Monaca, Pa., as Army Corps Pittsburgh District Chief Col. Nicholas Melin looks on August 20.
Photo by Jeff Yoders/ENR

Much of the original auxiliary lock chamber wall was being demolished by excavator-mounted jackhammer attachments from Trumbull-Brayman barges on the day of the site tour.

"We're building a new main[-sized] chamber over the footprint of the auxiliary chamber," said Col. Nicholas Melin, Corps Pittsburgh District commander.  "If you can imagine we're going to be demoing the auxiliary chamber here and building a new 600-ft chamber right over that footprint."

Melin said only one barge at a time can go through Montgomery's existing auxiliary chamber so shutting down the main chamber would essentially turn moving a nine-barge tow into a full day of breaking apart and reassembling the barges. Cunningham said the new middle wall will be right next to that and will need to be built in the dry once the project switches means and methods. 

 "We don't want to destabilize our new middle wall," Melin said. "We're not excavating below that wall and destabilizing that. We're tying in our cofferdam plan to some other in the wet models that allows us to pull all that material, all that water, out of there," so the construction of the new middle wall can take place in the dry. 

Reporters and officials were shown a detailed Autodesk Navisworks model from the Corps' Engineering Research and Design Center in Vicksburg, Miss. The model for Montgomery was being used by Trumbull-Brayman not only for construction activities, but for quantity take-off and purchasing decisions for the project. Dening pointed out that even as Montgomery's concrete batch plant was still under construction, steel was able to be purchased for the lock doors that will be installed in a later phase of the project and fabrication could begin on them. 

 "The Corps is actually switching to 100% Autodesk - that just was a recent mandate that came out," Melin said. "All our major mega navigation projects we have design responsibility for, so that's the Soo [Michigan] lock, that's the Kentucky lock, that's Montgomery, that's lock 25 in LaGrange Ill., we have a lot of lessons learned and best practice sharing organically. We also have a major database of lessons learned that we're tracking as well."

Corps officials said the process of switching entirely to Autodesk design products such as Revit, Civil 3D and AutoCAD began in 2018 and was largely completed by 2023. Another long-lead item is the concrete batch plant being built on a hillside above the remote lock and dam. Because the Corps uses largely proprietary concrete mixes for lock and dam projects, building the plant is essential to later phases of construction. Cunningham said after it's completed this winter, conveyors will be built across the existing structure to deliver concrete right to site ready to place. 

There are three lock and dam modernization projects in the Upper Ohio Navigation master plan, Montgomery, Dashields and Emsworth.