Tunnel boring machine arrives in Alexandria to dig waterfront tunnel

Dec 29, 2023

ALEXANDRIA, VA.—A welcome reception was held in Alexandria, Va. recently to celebrate the arrival of Hazel, a new 380-ton, 14-feet-eight-inch-tall tunnel boring machine (TBM) that will dig a new waterfront tunnel in the area.

The machine, which made its way from Schwanau, Germany, to Alexandria, was unveiled by AlexRenew, Alexandria's wastewater authority.

The arrival and dedication of the TBM is a major milestone for RiverRenew, the largest infrastructure project in Alexandria's history and a critical part of meeting a state-mandated deadline to remediate combined sewer overflows by July 1, 2025, indicates a release.

Once lowered more than 100 feet below ground, Hazel will dig a new two-mile waterfront tunnel with little service interruption. The project is estimated to take just over a year and following completion, the RiverRenew tunnel system will prevent over 120 million gallons of combined sewage from polluting the Potomac River, Hunting Creek and Hooffs Run each year.

TBMs are typically named prior to launch per 14th-century mining traditions and have historically carried a feminine name, as underground workers looked to Saint Barbara for protection. Keeping with this long-standing custom, AlexRenew nominated the names of six women who made outstanding contributions to Alexandria, the environment or the engineering and construction fields, the release states.

Following an online poll, the TBM name was unveiled at the ceremony in recognition of Hazel Johnson, one of America's leading women pioneers for environmental justice who dedicated her life to fixing ecological issues.

Environmental engineering and construction services firm Brown and Caldwell serves as the owner's adviser on the RiverRenew program.

"It really is a generational project — for us as engineers and planners — but also for Alexandria and future generations who will benefit from healthier waterways," said Brown and Caldwell project manager Justin Carl in a statement.