Tunnel Achievement Award Presented to Jefferson Barracks Tunnel

The Jefferson Barracks Tunnel for the Metropolitan St. Louis Sewer District was formally presented with the Tunnel Achievement Award Sept. 9 as part of the 17th annual Breakthroughs in Tunneling Short Course. The course took place Sept. 9th through 11th on the campus of the University of Denver.

The project team included: Owner: Metropolitan St. Louis Sewer District (MSD); Contractor: Affholder; Tunnel Designer: Jacobs Engineering Group; CM: Shannon & Wilson; Contractor’s Consultant: Brierley Associates; TBM Manufacturer: Robbins; Subcontractors: Case Foundation (shafts), ACT (pre-excavation grouting), Williams Tunneling (tunnel construction and carrier pipe installation), Goodwin Brothers Construction (intake construction).

The Jefferson Barracks Tunnel was recognized for the ability of the project team to overcome extreme challenges through collaboration and teamwork Designed to address sewer overflows as part of MSD’s Project Clear, the Jefferson Barracks Tunnel stretches 17,800 ft (3.37 miles) parallel to the Mississippi River. The tunnel is 11 ft ID and lined with 7-ft Hobas fiberglass pressure pipe.

Project challenges included an alignment that traverses an area of river bluff karst, a porous limestone containing numerous caves and sinkholes caused by erosion. The tunnel had to be carefully aligned to avoid the difficulty and expense of building in such challenging conditions. Engineers determined the best solution was to bore below the karst zone and tunnel into limestone bedrock at 150–230 ft below the surface. Additionally, the site traversed sensitive areas that could not be disturbed, including the Jefferson Barracks National Cemetery, Jefferson Barracks Park (the site of an old Army base which is listed on the National Register of Historic Places), a VA hospital, a high school and an interstate highway.

However, despite the team’s best planning efforts, the TBM encountered a karst feature. Due to substantial inflows encountered, tunneling was put on hold as the team considered their options for going forward.

The plan implemented included the construction of a 200-ft deep, 40-ft diameter recovery shaft in stable ground and a 200-ft long conventionally mined tunnel to rescue the machine. In July 2021 the team completed the access tunnel to the stalled TBM, and it was advanced to the recovery shaft and removed for refurbishment. The replacement 13.5-ft Robbins Main Beam TBM was relaunched out of the same shaft in Spring 2022 – commencing what became Phase 2 of the project. The new machine was designed to detect karst and other underground features by probing. The unique machine was equipped with enhanced 360-degree probe drilling capabilities, as well as versatile ground support options including McNally crown support, wire mesh, ring beam erector and roof drills.

The TBM holed through at the reception shaft on Dec. 20, 2022, with no major additional karst zones being encountered. One smaller karst area was encountered after the re-launch but was successfully handled with grouting from inside the tunnel, as designed.

As of September 2024 all work on the project has been completed.

Tunnel Achievement Award Winners
Established in 2012, the Tunnel Achievement Award recognizes successfully completed projects that demonstrate innovation and teamwork and provide benefits to the community. The award is presented by the organizers of the Breakthroughs in Tunneling Short Course in conjunction with TBM: Tunnel Business Magazine.

• 2024: Jefferson Barracks Tunnel, St. Louis, MO
• 2023: Mill Creek Drainage Relief Tunnel, Dallas, TX
• 2022: Kemano T2 Tunnel, Kitimat, BC
• 2021: DigIndy Tunnel System, Indianapolis, IN
• 2021: Gary Brierley, Dr. Mole Inc. (Lifetime Award)
• 2020: Regional Connector, Los Angeles, CA
• 2019: Ohio Canal Interceptor Tunnel, Akron, OH
• 2018: Northgate Link Extension, Seattle, WA
• 2017: Blue Plains Tunnel, Washington, DC
• 2016: Lake Mead Intake No. 3, Las Vegas, NV
• 2015: Bay Tunnel, San Francisco, CA
• 2014: Port of Miami Tunnel, Miami, FL
• 2013: East Side CSO, Portland, OR
• 2012: No. 7 Extension, New York, NY
• 2012: Dr. Martin Herrenknecht, Herrenknecht AG (Innovation Award)