The long-dormant transit tunnel that lies two levels beneath the outer commercial drive will soon seal a piece of MEM history.

The tunnel is being filled with a material called “cellular concrete,” which is a lightweight flowable material made by mixing cement, water, and preformed foam air bubbles which creates a lightweight porous structure.

In the time-lapse footage above, you’ll see the progress through April 25, 2025. The approximately 60-day process is one week in, and is estimated to reach completion in June.

The goal is to pump 1,000 cubic yards per week. When completed, approximately 55,000 cubic yards will have been used – enough material to fill 17 Olympic-size swimming pools!

Before sealing off the tunnel for good, a set of ground water pumps from the tunnel to the east will need 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.

If you’d like to read more about the history of the transit tunnel, check out our story, The History of MEM’s Sub-Basement Transit Tunnels.

For the latest on the Terminal Modernization and Seismic Program (TMSP) progress, visit our MEM on the Move webpage: https://flymemphis.com/mem-on-the-move/.