Site Tour

Get inspired by participating in our off-site field trip and technical tour to the Mill Creek Drainage Relief Tunnel. Learn how others in the tunneling industry are improving methods, overcoming obstacles and reaching operational goals.

Wednesday, November 17, 2021

The 2021 Cutting Edge program will, subject to restrictions, include an optional visit to the City of Dallas’ Mill Creek/Peaks Branch/State-Thomas (MCPBST) Drainage Relief Tunnel, which is currently under construction by the Southland Mole Joint Venture (SMJV).

The MCPBST Drainage Relief Tunnel will provide 100-year flood protection for nearly 2,200 commercial and residential properties east of downtown Dallas, eventually carrying a maximum flow of nine million gallons per minute when it is completed in 2023. Halff/COWI are the designers of the project, with Black & Veatch providing construction management.

The 5-mile (8.04km) tunnel is being excavated through Austin Chalk using a 37.58ft (11.45m) diameter Main Beam Robbins TBM – named ‘Big Tex’ in honor of the famous Texas State Fair – at depths of 100ft to 180ft (30.5m to 54.9m) below the surface.

A key innovation on the project is that the tunnel’s diameter will change mid-drive thanks to an in-tunnel TBM conversion process. The TBM will first tunnel 9,000ft (2.74km) of the alignment at its full diameter, then the team will work within the tunnel to remove outer sections of the cutterhead to convert the diameter of the machine to 32.42ft (9.88m). Once the conversion process is complete, Big Tex will continue to tunnel the remaining 17,000ft (5.2km) of the project.

More specific information about transportation and PPE will be provided closer to November.