The construction project at Locks and Dam 4 at Monongahela River mile 41.5 is nearly complete and ready to refill with water before installing the miter gates in Charleroi, Pennsylvania, May 23, 2023. The chamber is part of the Lower Mon Project, sometimes referred to as a "mega project" because of its size and scope. Nearly 90 percent of the work on the project is now complete, at a $1.2 billion cost. It began with the installation of a new gated dam at Braddock (Monongahela River Locks and Dam 2), replacing the former fixed-crest dam, before work shifted to Charleroi. (U.S. Army Corps of Engineers Pittsburgh District photo by Michel Sauret)