The Mill Creek/Peaks Branch/State Thomas Outlet Tunnel (Mill Creek Tunnel) reached a major milestone last month

Featured Photo: A glimpse below of Big Tex’s breakthrough at Mill Creek Tunnel. Image: Halff Associates

Published: 2022-08-20

Richardson (Dallas County) – The Mill Creek / Peaks Branch / State Thomas Drainage Relief Tunnel (Mill Creek Tunnell) reached an important milestone last month, when the tunnel boring machine (TBM) bored through the wall of the shaft to complete the excavation phase.

The large-diameter tunnel boring machine, nicknamed “big tex“, completed a 5-mile trip that included 2 miles of excavation 37.5 feet in diameter and 3 miles of excavation 32.5 feet in diameter. Big Tex was the largest hard rock tunnel boring machine in service in the United States during the excavation phase.

Members of Halff’s Mill Creek Tunnel crew pose for a photo July 25 after the completion of the shaft wall excavation.

Construction of the tunnel’s concrete lining will begin in the next phase of the project. When completed, the Mill Creek Tunnel will consist of 2 miles of 35 foot diameter tunnel and 3 miles of 30 foot diameter tunnel.

Half led the design effort for this $320 million drainage relief project, including the centerpiece of the Mill Creek Tunnel, which is being constructed at depths reaching 170 feet underground. When complete, the project will provide flood protection during the 1% annual lucky flood (or 100-year flood) for nearly 2,200 commercial and residential properties in East Dallas.

The project team includes the owner, City of Dallas, lead design firm Halff Associates, Inc., construction manager Black & Calfskin and building contractor Southland Mole Joint Venture.

Modified from press release.

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