HRBT expansion boring? Yes and no
Already the largest project ever tackled by the Virginia Department of Transportation, the $3.8 billion Hampton Roads Bridge-Tunnel expansion will kick into gear later this year when a $70 million custom-built tunnel boring machine (TBM) begins carving out an underwater path for twin two-lane tunnels.
Construction on the HRBT expansion, which will increase tunnel and roadway capacity along 9.9 miles of Interstate 64 between Hampton and Norfolk, began in October 2020 and is scheduled for completion in November 2025.
It’s only the fourth time that a tunnel boring machine will be used on a U.S. roadway project, including tunnels in Seattle, Miami and the Parallel Thimble Shoal Tunnel under construction at the nearby Chesapeake Bay Bridge-Tunnel.
Standing the height of a four-story building and measuring the length of a football field, the TBM’s front end consists of a 46-foot-diameter rotating cutterhead that bores through soil and rock strata as it creates an approximately 45-foot-wide opening for the new tunnels. Virginia Beach middle schoolers dubbed the machine “Mary” after Mary Winston Jackson, the late NASA mathematician and aerospace engineer depicted in the 2016 film “Hidden Figures.”
Hampton Roads Connector Partners, a joint venture led by Dragados USA Inc., is the design-build team for the project. It contracted with German firm Herrenknecht AG to fabricate the boring machine, which arrived at the Port of Virginia aboard three vessels in December. Crews have been preparing a 70-foot-deep launch pit on South Island, near Norfolk, where the TBM will be assembled and readied to start excavation by mid-2022.
“We are working aggressively to get the launch pit ready,” says James Utterback, VDOT’s project director for the HRBT expansion. “This is one large project that has a series of big projects inside it and lots of unique construction operations that need to come together.”
Once underway, a hydraulic cylinder will move the TBM about 50 feet per day as the cutterhead bores a two-lane tunnel to North Island, near Hampton, a process expected to take about a year. At North Island, it will take 4 to 6 months to rotate the machine on a specially built turntable in preparation for its return trip, boring a parallel twin two-lane tunnel to South Island. The return trip is expected to take 10 to 12 months, with the total process taking about 2½ years.