Manhole Fires

Winter is in full effect. With cold weather comes snow and ice. Winter in Boston means traffic will be worse than the days before the “BIG DIG”. Driving on slippery roadways necessitate the placement of ice-melting salt onto roadways to make them safe. When the salt is put on top of slick roads, the result is a melting of the ice and snow that coats them. As a result, the roadway becomes safely passable but at a price. The mixture of salt, melted snow, and ice filters into manholes, coating the underground electrical wiring and equipment. This salt-water mixture is very corrosive and causes the wiring, transformers, and other elements of the underground electrical delivery system to deteriorate. Often this results in arcing exposed wires. The arcing, burning wire generates various toxic and combustible gases including high concentrations of carbon monoxide (CO) and neoprene gas. These gases are contained in the black noxious smoke billowing out of the manhole at a manhole fire.

Firefighters responding to these incidents should be aware of the many hazards that may accompany this phenomenon.

1. The black smoke can at any moment suddenly ignite, exposing people and vehicles nearby. A person inside a car parked over such a manhole would be severely injured or killed should the smoke ignite as he tried to move the parked car away from the manhole.
2. The ignition can be explosive, sending the 300-pound manhole cover flying upwards of 30 feet into the air.
3. Manholes are connected underground to other manholes by electrical conduit through which wires pass. Fire in one manhole can spread to other nearby seemingly uninvolved manholes, which can suddenly start to smoke, erupt into flames, or blow their covers into the air.
4. The explosive and toxic gases created at these incidents can pass through underground conduit into surrounding structures served by the underground electrical delivery system. The result can be overcome occupants and an explosive atmosphere in the electrical service box or the entire building. These explosive gases can also travel along underground conduit and enter and fill up hollow street light poles. A spark from a traffic light control box can ignite these gases, causing the lights' access panels to blow off the poles.
5. Salt water is a good conductor of electricity and, as a result, manholes and grates covering underground electric equipment have become energized, resulting in the injuries and deaths of pedestrians, pets, and other firefighters. Anything metal such as a bus stop shelter, curb drains, or even a nearby hydrant may become charged. ALL MEMBERS MUST ALWAYS USE CAUTION! (Fire Engineering, 2004)

When responding to these incidents take the following actions and precautions:

1. Stay clear of the trouble manhole and any other nearby covers.
2. Attempt to determine who owns the manhole (NSTAR, MBTA, Telephone, etc…)
3. Find and stay clear of the next manhole on either side of the trouble manhole.
4. Stop any traffic that might be endangered by a flying manhole covers.
5. If first arriving companies observe smoke or flames emitting from the manhole, notify Fire Alarm of a “confirmed manhole fire” and establish a “Hot Zone”. (Fire Alarm shall notify appropriate agency to respond.)
6. Company Commanders shall assume the manhole contains transformers and switchgears cooled with mineral oil containing PCB’s and position the apparatus and members to avoid any contact with smoke or fumes.
7. Attempts should be made to remove the manhole cover and extinguish the fire by filling the manhole from a safe distance. NOTE: Do not flow it directly into the manhole from a hose line. Bounce it off of the street and let it flow along the ground into the manhole or consider flowing water from an unmanned open coupling into the manhole. WATER SHALL NEVER BE PLAYED INTO MBTA MANHOLES!
8. Consider removing covers of other manhole inline with the one involved to relieve pressure buildup.
9. Check nearby structures for carbon monoxide and shorted power lines and evacuate them, if necessary.
10. Do not attempt to kill the power to a building, even if its lights are blinking; there could be an explosive atmosphere in the electric panel box. A spark created by opening the main cut-off could result in an explosion.
11. Be aware that the danger area around a burning manhole may extend to other manholes, nearby street light poles, and traffic control boxes as well as the surrounding structures. If electric service is delivered by a combination of overhead and underground wiring, be aware that a manhole fire can extend up to the overhead wires via a connecting conduit. This would put the run of overhead wiring in the danger area.

Extensive testing and research has found that applying water to manhole fires is both a safe and effective method of extinguishment. The water actually controls the fault by cooling the equipment to the point of controlled burning. Water can be used because of extensive grounding of cables and equipment throughout these manholes, however, UNDER NO CIRCUMSTANCES SHOULD FIRE DEPARTMENT PERSONNEL ENTER A MANHOLE, with the only exception being a confined space rescue.

For more information regarding manhole fires, refer to the video on manhole fires located at each District Chief’s Office.

Boston Fire Department SOP #49B Special procedures and precautions for incidents involving manholes.

Fire Engineering, 2004

Special Thanks to F.L. (BFD E-22)

Test post

Great repair job. Although I would think duct tape would be stronger.