Tunnels

Flatiron's tunnel expertise is comprised of both conventional and top-down construction methods, including cut-and-cover, immersed tube tunnels, tunnel boring and ground freezing. Flatiron has also performed construction engineering for the largest jacked-box tunnel project known in the world.

I-90/I-93 Interchange - Boston, MA

Flatiron reconstructed the intersection of Interstate 93 and the eastern terminus of Interstate 90. This $420 million six-year undertaking was comprised of three different types of work: viaducts, boat sections, and tunnels. Three jacked-box tunnels were constructed under…

Lenihan Dam Outlet Modifications - Los Gatos, CA

At the foot of the Santa Cruz Mountains, Flatiron replaced the deteriorating outlet structure for the 50-year-old Lenihan Dam - a 1,000-foot-long earthen barrier holding water stored at the Lexington Reservoir in Los Gatos, Calif. The project was a seismic upgrade for…

Ted Williams Tunnel - Boston, MA

As part of the Central Artery/Tunnel Project, Flatiron constructed this immersed tube tunnel under the Boston Harbor to connect the Boston Logan International Airport with downtown Boston's portion of I-90. This 3,850-foot tunnel was designed using 12 tube segments,…