There has been considerable talk recently about tunneling technology, and how much more it can be improved. No doubt, improved technology helps make tunneling faster and cheaper, and even allows tunnels to be built that perhaps would not have been possible in the past.
The truth is that tunnel technology has been evolving at a steady pace. Culminating in recent years with record-setting projects and notable firsts that have continued to expand the envelope of tunneling in the United States. In particular, the TBMs for Southern Nevada Water Authority’s Lake Mead Intake No. 3 and the New York DEP’s Rondout Bypass Tunnel raised the bar for tunneling under high water pressure, and Washington State DOT’s SR 99 Tunnel and Florida DOT’s Port of Miami Tunnel set standards for large bored highway tunnels.
And that is just the TBMs. WiFi communication, real-time monitoring and automation complement improvements to materials and processes including tunnel liners, waterproofing systems and additives for optimizing TBM performance in a variety of ground conditions… to name a few.
Ultimately, however, technological improvements by themselves are meaningless without a willingness to accept them. Historically, there had been a reluctance in the United States to jump on board with new (i.e., untested/unproven) technology. And understandably so: No one wants to be the “guinea pig” or explain to stakeholders why a project went sideways. Tunnel projects are, for the most part, built to serve the public, built with public money (typically) and oftentimes built in proximity to business and residences.
But in the past 10 years, we ave seen a willingness to embrace new approaches and innovative technologies, beginning perhaps with adopting new contracting strategies, specifically design-build. Design-build encourages innovation by tapping into the contractor’s substantial knowledge, while potentially reducing the cost and duration of a project. Continuing this trend, we are seeing P3s as an alternative to tradition public financing, which could spur even more tunnel work.
During that same time period, agencies have shown an increasing willingness to take on new approaches such as the previously mentioned record-setting projects – among others. Looking ahead, I see this trend toward embracing technology continuing.
In Virginia, VDOT announced that the new Hampton Roads Bridge-Tunnel Expansion project will include a bored tunnel across the harbor – a first for the department. The bored approach reduces impact on the marine environment while reducing impacts to commercial and military shipping in the channel. All 10 existing highway tunnels in the Hampton Roads area have been built by immersed tube.
In California, the Santa Clara Valley Transportation Authority approved a single bore option for the upcoming BART extension under downtown San Jose. This single-bore approach reduces surface impacts, optimizes station construction and eliminates the need to construct cross passages. Construction of a single-bore subway construction would be a world-class project and a first in North America.
With demand for tunnels forecast to increase across all sectors (water, sewer, subway, high-speed rail, highway), the need for improved methods to increase efficiency and decrease cost will continue. And no doubt the industry will continue to meet the demand.