Officials in Alexandria, Virginia, will ramp up a tunneling project well below the city’s surface next month in an effort to divert sewage from spilling into the Potomac River.
The 380-ton tunnel boring machine named “Hazel” was lowered 138 feet — or about 12 stories — into a pumping shaft near Alexandria’s waste water treatment plant last month. The boring machine will create a two-mile-long tunnel from the wastewater treatment plant to Pendleton Street.
The boring will begin during the second week of October.
“Hazel will mine a two-mile-long tunnel, about 11,500 feet and about 40 feet per day. She’ll excavate the soil, pressurize the ground to prevent ground movement. And then behind her will be erecting a precast tunnel liner,” said Justin Carl, the program manager at Alex Renew, the city’s sanitation authority.