by Ken Pantuck
DC Water dedicated its second Tunnel Boring Machine (TBM) on December 12, 2014. It has been named “Nannie”, in honor of Nannie Helen Burroughs, a prominent 20th century African-American educator, civil rights activist, and Washington resident. This TBM will join another – called “Lady Bird” – as part of Washington’s strategy to reduce combined sewage overflows into the Anacostia and Potomac Rivers when it rains.
The huge cutting head – 26 feet in diameter – will soon be lowered down a nearby drop shaft 100 feet below the surface and placed on railroad tracks. Like a caterpillar, more segments will be added to the drilling machine, growing Nannie to a total length of 350 feet and a weight of 1,248 tons (the equivalent of nearly six Boeing 747s) when fully assembled and functional. As the TBM moves forward, curved six-foot cement pieces are pressed against the tunnel wall to create a strong circular structure. On average, Nannie is expected to create 52 to 64 feet of tunnel each day.
The Catholic archbishop of Washington, Cardinal Donald Wuerl; EPA’s Deputy Assistant Administrator for Water, Ken Kopocis; DC Water Board Chairman and City Administrator Allen Y. Lew and DC Water General Manager George S. Hawkins, spoke at the dedication event. Mr. Lew christened Nannie with a bottle of DC tap water. Cardinal Wuerl blessed the machine and asked for God’s protection of the miners. We often forget that tunneling, whether it is for mining, subways, highways, or sewers, is not without risk. I was told that a statue of Saint Barbara, the patron saint of miners, is often placed near tunneling construction sites.
Having myself been underground in the main tunnel being mined by Lady Bird, I can attest that it is among the hardest and most challenging jobs in construction. The workers or miners come from all over the world. Because they are experts in what they do and in the operation of this type of machine, the workers that are in DC today could be constructing a subway system in Dubai or a highway tunnel in Europe next year.
A third TBM will start next spring to complete the 13-mile Anacostia River segment. When finished, DC Water’s Clean Rivers Project is expected to capture 98% of storm-related combined sewage overflows into the Anacostia River and improve its water quality.