438,000km Natural Gas Network Destroyed Entire Neighbourhood

Fifteen acres of San Francisco suburbs have been reduced to burnt rubble because of a glitch in the massive US natural gas pipeline infrastructure. How did this happen and perhaps more importantly what exactly is going on down there?

At the moment, authorities aren't entirely certain what sparked the explosion - though San Francisco fire department chief Joanne Hayes-White believes the rupture might have been the result of a plane crash.

But even before the final answers are uncovered, the catastrophe - already declared a state of emergency - should prompt us to look downward at the gigantic network of highly flammable (to say the least) gas that courses across the continent. Traversing the US like an interstate highway system is an intricate network of large-diameter pipes. Step upon any given square mile of this network, and you're standing on top of 113,000 cubic metres of combustible gas. That's enough to keep a stove lit for 40 years straight. c

To keep the gas flowing and stoves burning, vast numbers of "compressors" are employed to artificially shove gas through the pipes, creating pressures of up to 105.5kg per square centimetre. According to the American Gas Association, these pressure levels are maintained far lower than the pipes are designed to contain - but at these pressure levels, if there's a leak, gas will squirt out quickly.

And it appears that's just what happened, with local residents saying they smelled natural gas in the air for days before the explosion, which has so far killed four people, injured 52 more and destroyed almost 50 buildings. Ignited leaked gas could have ruptured one of the pipelines, setting aflame a volume that even at relatively low residential pressures is still hundreds of kilos of explosive gas. Enough to destroy a large part of San Bruno.