How exploding manhole covers work

 

There have been recent reports in the news of exploding manhole covers. This post covers some of the common causes and options for prevention. 

Cause: A combination of flammable gases and a spark cause an expansion of air volume that lifts  the manhole cover in the air.

Prevention: 

1. Slotted manhole covers that allow pressure relief. (This will not work for sanitary sewers as it allows storm water to enter the sanitary sewers). 
2. Inspection of wiring in areas below ground to assure the wires are in good shape.  This is often done using infrared cameras.
3. Early detection of flammable gasses or liquids in the underground utility system.
4. Proper disposal of flammable liquids as hazardous waste.
5. Avoid using sparks or flames near manhole covers. 

How it Works describes the circumstances for an exploding manhole. 

The science behind exploding manhole covers - 2 min.