A dormant transit tunnel beneath Memphis International Airport is being sealed with cellular concrete.
The concrete pour began this week and is expected to be completed in June.
Approximately 50,292m3 of concrete will be used to complete the task and the goal is to pump 91.4m3 per week.
Before sealing off the tunnel, a set of ground water pumps from the tunnel to the east had to be relocated above the tunnel.
Filling the transit tunnel is required to ensure that the airport structures that sit above it meet seismic and safety codes.
The tunnel dates from the 1970s when Memphis International Airport added Terminals A and C. The sub-basement transit tunnels were imagined as the future home of a tram system connecting passengers between future remote terminals, or as a connection to a future subway system. As time went on, expansion plans changed for remote terminals, the subway system connection did not materialise, and no alternative uses for the sub-basement transit tunnels were found.
The walls and ceilings of the tunnels have deteriorated significantly and now the airport has begun work on the Terminal Modernisation and Seismic Program, the tunnel system must be addressed because of its inability to withstand seismic activity.
Memphis and the surrounding areas are located within the New Madrid Seismic Zone, making the aiports 1960s and 1970s structures vulnerable to potential earthquake damage. The construction of the terminal, including the tunnel system, predates building code requirements for seismic resilience.
