Five people were injured in a manhole explosion in the Bronx, NYC, last Friday night. A manhole located on Saint Ann’s Avenue near East 156th Street exploded under a parked car. 3 civilians and 2 police officers were injured by flying debris during the explosion. The civilians were treated at the scene of the accident while the two police officers were transported to the hospital to be treated.
Con Edison crews were still making repairs yesterday working to fix underground wires in a narrow area of Saint Ann’s Avenue.
Manhole explosions can be very dangerous in a busy city like New York. In such explosion the cast iron cover that can weight between 85 and 300 pounds is sometimes propelled into the air from 1 foot to 50 feet depending on the intensity of the explosion. Manhole explosions often occur during the spring because all the salt used to make the roads safer is corroding the underground cables. However other factors such as aging, overload or rat biting can also damage the cables insulation. When the cable insulation is damaged, wires start to touch each others creating heat to the point that the insulation catches on fire and releases gas. The pressure from the gas then builds up inside the manhole. The defective electrical wires can then ignite the gas and cause a potential explosion.
Depending on the pressure, the manhole cover can be ejected in the air and become a real danger to pedestrians. The most dangerous covers are the solid ones. They are being replaced by slotted covers that allow the gas to be released less violently. They can also give early warning of a potential explosion.