Ernest Tremmel was a civil engineer who worked on the Manhattan Project for the Army Corps of Engineers, as a purchasing officer. He went on to work for the Atomic Energy Commission (AEC) for many years and as a nuclear energy consultant. In this interview, Tremmel discusses the secrecy of the Manhattan Project and how he learned the goal of the project. He recalls interacting with General Leslie R. Groves, Admiral Hyman Rickover, and other AEC commissioners as well as directors of energy companies. Tremmel explains what made this period, and the quest to build nuclear reactors, so exciting. He also remembers witnessing a nuclear bomb test after the war.