C.J. Mahan work crews position concrete delivery trucks onto a barge Sept. 20, 2023, on the upstream side of Chickamauga Dam that placed 148 cubic yards of tremie concrete into a tremie pipe and shaft on the bottom of the Tennessee River for the first of 14 shafts for the upstream approach wall piers. The U.S. Army Corps of Engineers Nashville District Upstream Approach Wall construction is an integral part of the Chickamauga Lock Replacement Project in Chattanooga, Tennessee. (USACE Photo by Matthew Curvin)