News Extra: Recent fatal blasts highlight USA’s ageing gas pipeline problem
01 May 2014
An explosion in New York City’s East Harlem district in early March killed two, injured 16 and destroyed two buildings. Although no investigation results have been published yet, Robert Sumwalt of the National Transportation Safety Board, which is investigating the blast, said the high soil methane readings indicated natural gas might have triggered the explosion.
There have been a number of fatal pipeline incidents in recent years, including the natural gas explosion in Allentown, Pennsylvania, which killed five people in 2011, that have been linked to the failure of ageing pipeline infrastructure across the USA.
In East Harlem, part of the buildings’ gas supply was installed in 1887, while in Allentown the pipe was dated to 1928.
The gas mains that cause most concern are made of cast iron, many of them dating back to before the Second World War. Cast iron pipes are vulnerable to corrosion, and their rigidity makes them susceptible to stresses, including construction activity and vehicle traffic above.
Utilities have replaced most of the old iron infrastructure over the past several decades. But according to the federal regulator, the US Pipeline & Hazardous Materials Safety Administration (PHMSA), nearly 46,000 miles of iron mains and subsidiary lines were still in place in 2012, the most recent year for which data is available. Even though only 2.6% of the nation's distribution lines are still made of cast iron, 11% of the incidents that caused accidents or fatalities have involved cast-iron pipes.
According to PHMSA data, the large cities of the Eastern Seaboard have far higher proportions of iron pipes, given the difficulty of replacing them under busy streets and buildings. Philadelphia has 50% iron mains, Washington DC 35% and New York City 30%. US government data shows that the cities that still have the highest percentage of cast iron mains also have higher than average rates of methane in the atmosphere, thought to be caused by leaks.
Other types of ageing gas main have also caused serious incidents. In September 2010 a gas pipeline explosion in San Bruno, California, killed eight and demolished a whole suburban block in the San Francisco suburb.