News

May 11, 2023

Hazel Tunneling Under Old Town

The tunnel boring machine is working her way east toward the Potomac River. May

The tunnel boring machine is working her way east toward the Potomac River.

May 12, 2023

8:00 a.m.

AlexRenew

by John Adam Wasowicz

AlexRenew, the advanced water public utility serving more than 300,000 customers in Alexandria and parts of Fairfax County, provided tours last weekend of its ‘Hazel’ tunnel project.

The massive environmental project will correct Alexandria's combined sewer problem by connect overflow pipes and returning the runoff to the treatment facility prior to being discharged into the Potomac River. Currently, when the sewers overflow from excessive runoff, untreated wastewater is dumped directly into the river.

Hazel is the name of the subterranean tunnel boring machine (TBM) that is now constructing the Waterfront Tunnel. Most TBMs are named after women, and ‘Hazel’ is named after Hazel Johnson, an environmental justice pioneer. "TBMs have historically carried a female name, stemming from a tradition from the 16th century when miners and tunnelers are said to have looked to Saint Barbara for protection and luck while working underground," AlexRenew explains on its website.

As ‘Hazel’ digs her way through the earth 130 feet below the surface, she is constructing a huge cement tunnel in her wake. The tunnel is constructed using pre-fabricated panels. As Hazel moves along, construction crews build a conveyer belt to move debris out of the tunnel and back to the surface.

Last weekend, for the first time, AlexRenew invited the public to take a tour of the tunnel that Hazel is creating. Participants in the tour were 130 feet below the surface, or about 13 stories underground.

Each person participating in the tour wore a hard hat, gloves, protective eyewear, and a vest. AlexRenew personnel provided a safety briefing at the outset, and the utility's personnel were located throughout the site to ensure safety and answer questions.

The tour commenced with a ride down a seven-story deep hole in a steel cage, settling on the entrance to the tunnel.

Once at the entrance, visitors could observe the completed initial section of the project, which has already dug from the plant in the Eisenhower Valley to an area beneath Patrick and Henry Streets. Currently, Hazel is just east of Church Street.

When the 13-ft. diameter tunnel is completed, it will be 2.3 miles long, and will have a drop of 16 feet over that distance to ensure a gravity fed flow toward the waste treatment plant.

May 12, 2023

8:00 a.m.