Adam Walker, U.S. Army Corps of Engineers Nashville District project manager for the Chickamauga Lock Replacement Project, briefs Douglas Lamont, senior official performing duties of secretary of the Army for Civil Works, on the benefit of a new computer model that allows the Nashville District to analyze existing stresses and forecast future stresses where the lock has experienced structural problems resulting from alkali aggregate reaction between the alkali in the cement and the rock aggregate. The reaction results in a physical expansion of concrete structures. The briefing took place at the Chickamauga Lock Replacement Project Resident Engineer Office at Chickamauga Dam in Chattanooga, Tenn., Feb. 28, 2017.