The United States’ second–largest underground power system, a complex network of 13,000-volt feeder cables delivering electricity to hundreds of thousands of residents and workers, lies buried beneath the District’s downtown.
But when one of those cables catch fire — watch out. Literally.
Like a bolt of lightning, sparks can ignite accumulated gases and, boom! Manhole covers from 85 to 300 pounds are violently expelled into the air as if they weigh nothing at all.
Just such an explosion and fire occurred early Wednesday in Southwest Washington along the National Mall, knocking out dozens of traffic signals and tying up traffic for miles during the morning rush. No one suffered an injury in the blast.
The D.C. Emergency Management Agency lists manhole cover explosions as one of the District’s 18 major hazards, alongside urban crime, hurricanes, terrorism and floods.
“It may be that in the next hazard analysis it won’t be on the list, but as of today it is still on the list,” EMA Spokeswoman Jo’Ellen Countee said.
The explosions, usually followed by power outages, are bound to happen, Pepco Spokesman Robert Dobkin said. Water floods the system. De-icer chemicals corrode cables. Wires rub against each other. Rats chew insulation.
The vast majority of manhole explosions occur in the sections of Northwest where the power grid is buried, specifically from downtown to Capitol Hill, north to Florida Avenue and west to Georgetown. Between February 2000 and August 2003, 107 explosions were reported citywide. No one was injured.
Pepco has installed thousands of slotted manhole covers, which can reduce blasts by releasing gas, throughout the District. But the manhole that exploded Wednesday morning was solid, Dobkin said.
A spate of underground fires and manhole blasts seven years ago led Pepco to rewire and upgrade its underground electric system in Georgetown. In Logan Circle last October, five manhole explosions shattered windows and forced pedestrians to reroute in the area of 13th and Q streets.
