380-Ton Boring Machine Arrives in Virginia to Dig New Waterfront Tunnel

380-Ton Boring Machine Arrives in Virginia to Dig New Waterfront Tunnel

Hazel will dig a 12-foot-wide, 2-mile-long tunnel to divert approximately 120 million gallons of sewage annually away from Alexandria’s waterways.

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A new 380-ton, 14-foot 8-inch tall tunnel boring machine (TBM) named Hazel has been unveiled by AlexRenew — Alexandria, Virginia’s wastewater authority — marking a significant milestone in its RiverRenew program to improve local waterways.

Making its way from Schwanau, Germany, to Alexandria, a welcome reception was held in mid-July to celebrate Hazel’s arrival, with over 100 attendees including City of Alexandria Mayor Justin Wilson.

“Today is a monumental day for Alexandria and our waterways. It’s a huge step forward in our commitment to deliver healthier waterways by 2025,” said AlexRenew General Manager Karen Pallansch at the event.

Typically, a TBM is named prior to launch, per 14th-century mining traditions. TBMs 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 whose outstanding contributions to Alexandria, the environment, or the engineering and construction fields, have paved the way for countless others.

As voted by Alexandrians via an online poll, the TBM was unveiled at the ceremony as “Hazel,” in recognition of Hazel Johnson, one of America’s leading women pioneers for environmental justice who dedicated her life to fixing ecological issues.

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. Once lowered more than 100 feet below ground, Hazel will build a new two-mile waterfront tunnel with little service interruption on a journey estimated to take just over a year to complete.

After 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.

Leading 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,” says Brown and Caldwell Project Manager Justin Carl.


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