Year: 2026

Cooperative Innovation at the Manhattan Tunnel Project: Digger Shields with Expandable Segments to Excavate Complex Fill

In what is billed as the most urgent infrastructure project in the U.S., the Hudson Tunnel Project is a critical piece of infrastructure to build two new passenger rail tracks between New York and New Jersey and rehabilitate the century-old North River Tunnel, which was badly damaged during Superstorm Sandy. In this paper, the authors will examine the cooperative structure that allowed the generation of a singular solution for the Manhattan tunnels, and the design of the digger shield machines and segments that are unique to the complexities of this urban infrastructure project.

Robbins celebrates TBM acceptance for Ellicott City North Tunnel

Robbins marked a major project milestone in Q4 2025 with the substantial completion of the factory acceptance test (FAT) for a refurbished Main Beam TBM at its Solon, Ohio manufacturing facility. The veteran machine, rebuilt in partnership with contractor Kiewit, is set to excavate the 1.5 km (0.9 mi) long Ellicott City North Tunnel, a critical flood mitigation project in Howard County, Maryland, USA.

The Robbins Main Beam TBM will bore through a mix of granitic rock beneath Ellicott City, minimizing surface disruption in the densely built, heritage-rich area.

The 5.6 m (18.4 ft) diameter TBM, originally manufactured by Robbins in 1991, has a distinguished global track record. The machine has successfully excavated multiple tunnels totaling more than 18 km (11 mi) and is now entering its next chapter as part of Maryland’s largest stormwater infrastructure project to date.
“Robbins and Kiewit share a long-standing partnership focused on quality TBM rebuilds and performance,” said Doug Harding, Robbins Vice President. “We are marking not only the acceptance of the machine, but also a continued commitment to delivering durable tunneling solutions that meet the evolving demands of major infrastructure projects.”

The Ellicott City North Tunnel is a centerpiece of Howard County’s Ellicott City Safe and Sound plan. Designed to divert stormwater runoff away from the historic downtown area—an area hit by multiple catastrophic floods in recent years—the tunnel will convey up to 26,000 gallons (98,000 liters) of water per second during major storm events. The TBM will bore through a mix of granitic rock beneath Ellicott City, minimizing surface disruption in the densely built, heritage-rich area.
“Excellent Engineers, Craft and Managers of Robbins and Kiewit have worked together at Robbins’ plant in Solon on a daily basis over the last year to achieve this milestone of substantial completion of the FAT. Synergy efforts were required and well delivered to get the TBM to increased technical and safety standards,” said Christof Metzger, Area Manager for Kiewit.

The TBM is expected to begin tunneling in 2026 following TBM assembly and launch shaft construction in Maryland. Its performance will be supported by Robbins’ field service team to ensure smooth operations throughout the project’s duration.