The 4.47m diameter TBM will dig the 3.2km (2 mile) Waterfront Tunnel, which will capture, store and transport combined sewage to AlexRenew, where it will be purified and returned to the Potomac River.

RiverRenew is the largest infrastructure project in Alexandria’s history and, once completed, will prevent over 120 million gallons of combined sewage from polluting the Potomac River, Hunting Creek and Hooffs Run each year. Project completion is schedule for July 2025.

As well as construction of the tunnel, which will be at a depth of 30m, the project includes diversion facilities to direct 130 million gallons of combined sewage into the tunnel system; the 800m-long (half mile), 1.8m-wide (6ft) Hooffs Run interceptor, pumping stations housed in two large shafts, and a superstructure to house pumping station equipment.

The TBM has been named Hazel after Hazel Johnson, one of America’s leading pioneers for environmental justice.