Marshall and his deputy district engineer, Kenneth Nichols, visited Tennessee on 30 June 1942 to examine the proposed location for the production plants in the Clinch River area, but Marshall chose to delay the actual purchase of the land until it was needed.
Groves's account says that: shortly after, Nichols replaced Marshall as District Engineer.. the Chief of Engineers asked me if I could relieve Marshall for a key overseas assignment, which would mean his promotion to brigadier.