Dozens of gas explosions rocked the Massachusetts towns of Lawrence, North Andover, and Andover on Thursday evening, sending smoke pouring into the air and residents reeling. There were 70 reports of gas odor, fires, and explosions.
At a press conference Thursday night, Massachusetts Governor Charlie Baker acknowledged that there were injuries, but didn't go into specifics. We now know that there was at least one fatality—18 year old Leonel Rondon—and perhaps dozens of injuries.
Gas pipelines in the affected areas were depressurized and power turned off as entire neighborhoods evacuated. School on Friday in the area, 25 miles north of Boston, was cancelled. Local authorities called for residents in those three affected areas who get their gas supply from Columbia Gas of Massachusetts to immediately evacuate. The event comes less than a month after a gas leak in Lawrence, Massachusetts also triggered an evacuation.
How gas lines work
Gas lines require pressure to push the gas from where it's gathered and processed to your home. During its journey it often travels at very high pressures in order to cross long distances (the transmission part of the gas delivery system).
Pressure is reduced when gas enters the system that carries it from the larger transmission lines to smaller distribution pipes into individual homes and buildings. This is also where the distinctive ‘smell’ of natural gas (which is odorless on its own) is added, so that humans can detect gas leaks.
The system must monitor pressure carefully at all points in the process to prevent it from building to unsafe levels, which can lead to explosions.
As the American Gas Association (a group that represents the gas industry) notes on their website: "As gas flows through the system, regulators control the flow from higher to lower pressures. If a regulator senses that the pressure has dropped below a set point it will open accordingly to allow more gas to flow. Conversely, when pressure rises above a set point, the regulator will close to adjust. As an added safety feature, relief valves are installed on pipelines to vent gas harmlessly, if a line becomes over-pressured and the regulators malfunction."
It is not yet clear what safety measures were or were not present in the affected Massachusetts communities.
Sadly, gas explosions are not rare events in the United States.
Propublica created a tracker in 2012 that examined pipeline incidents across the country from 1986 to the present. They found that half of the country's more than 2.5 million miles of pipeline were over 50 years old. As they age and are exposed to the elements, even thick steel pipes can corrode, and records from half a century ago can be spotty.