AlexRenew completes two-mile long, 100-foot deep tunnel to support a brighter future for the Potomac River


AlexRenew completes two-mile long, 100-foot deep tunnel to support a brighter future for the Potomac River

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After years of planning, coordination, and construction, the Waterfront Tunnel is complete. Early on the morning of March 21, Hazel the tunnel boring machine caught her first glimpse of daylight in 16 months as she was hoisted to the surface via a giant crane beside the Potomac River she was designed to help protect.

Over the last 16 months, Hazel and her highly-skilled crews have been carefully constructing a 2.2-mile tunnel under Old Town Alexandria and the Potomac River. This tunnel, left in her wake, will prevent millions of gallons of combined sewage from polluting the region’s waterways.

Hazel, named after environmental activist, Hazel Johnson, is a state-of-the-art tunnel boring machine, weighing in at 380 tons and longer than one-and-a-half football fields. On Wednesday, March 13, Hazel “broke through” a 100-foot-deep shaft immediately south of Oronoco Bay. This shaft will collect combined sewage overflows from an existing outfall and direct these flows to AlexRenew through the new 12-foot-wide, 100-foot-deep tunnel. The tunnel largely follows Alexandria’s waterfront before taking a sharp easterly bend in Jones Point Park, and then it’s a relatively straight shot back to AlexRenew below Church Street. This milestone signifies a crucial connection point, as it marks the integration of AlexRenew’s wastewater plant with all four of Alexandria’s combined sewer outfalls that date back to the 1860’s.

Hazel, the tunnel boring machine, sits in mud at the bottom of a shaft in Alexandria, VA.

“The collective efforts of our team to achieve this momentous milestone are nothing short of awe-inspiring. Their dedication and perseverance pave the way for a brighter future for the Potomac River,” says Justin Carl, General Manager and CEO of AlexRenew.

Now that Hazel's portion of the project is completed, crews will continue to work on the remaining portions of the RiverRenew project, including a new sewer interceptor; 12-story-deep, 65-foot-wide pumping station; and massive shafts that will function as a system to improve the health and quality of the waterways that connect us.

The ambitious project was recently granted a one-year extension by the Virginia General Assembly due to delays associated with Hazel’s manufacturing and shipping in late 2022. The project’s remaining efforts include the completion of a smaller sewer line along Hooffs Run, fitting out the massive drop shafts, and constructing a 12-story underground pumping station at AlexRenew. Work is anticipated to last through 2025.

“While Hazel is just a machine, she has embodied the heart and grit of our team, and like her namesake, has set a foundation for a healthier environment for our community, wildlife, and future generations,” says Carl.

In celebration of this milestone, AlexRenew will host an open house at 501 North Union Street on Saturday, April 13 from 10am – 4pm. The event is open to all ages and is pet friendly. Attendees will be able to learn about tunneling from our skilled and dedicated staff, see displays, and get a photo op with Hazel!


Looking down the shaft of workers standing on and around Hazel, the tunnel boring machine.