A 3D illustration of the downstream miter gate replacement project at Chickamauga Lock near Chattanooga, Tennessee. Comprised of 10 components (five on each side) that will be welded together, the gates will be over 70-feet tall and weigh over 800,000 lbs. The Chickamauga Lock replacement project, managed by the U.S. Army Corps of Engineers Nashville District includes designing a new 110-foot by 600-foot navigation lock to replace the current lock, which is necessary due to alkali-aggregate reaction, a chemical process that causes concrete to expand and crack, threatening the structural integrity of the lock. (USACE illustration by Joseph Cotton)