Streets were closed off and thousands of residents were forced to evacuate in several towns north of Boston on Thursday, after widespread gas leaks caused explosions and fires that destroyed numerous homes. Officials with Columbia Gas, the local gas utility, were mum about the cause of the gas leaks and fires, while Massachusetts Governor Charlie Baker said a full investigation would have to wait while police and firefighters dealt with the immediate emergency. But speculation focused on the theory that some sort of failure in the gas pipeline infrastructure allowed an over-pressure to affect home gas supply lines, causing gas leaks within homes across a wide area near the Merrimack River.
The New York Times had this report (see: “Massachusetts Gas Explosions: Dozens of Homes Burn in Andover and Lawrence,” by Katharine Q. Seelye, Farah Stockman, Jacey Fortin and Monica Davey). “Across the region, residents returned from work to find their homes burning and neighbors standing outside with no clear sense of what to do,” the paper reported. “Firefighters and other emergency workers raced from block to block, urging residents to evacuate to shelters that were hastily being opened. Along some blocks, the smell of gas hung in the air, and cellphones buzzed with evacuation warnings.”
“Earlier in the day, a local gas company, Columbia Gas of Massachusetts, had announced that it was ‘upgrading natural gas lines in neighborhoods across the state,'” the Times reported. “On Friday morning, the company said in a statement that workers would need to visit each of the 8,600 affected customers to inspect the gas meter.”
How Could This Happen?
In the immediate response to the disaster, answers were scarce. But a general web page from the American Gas Association (AGA) describes a extensive national and regional gas transmission and distribution system that transitions from high-pressure pipelines to lower-pressure individual hookups in several step-down stages, similar to the way the electric grid transitions from high-voltage transmission lines to lower-voltage service drops (see: “How Does the Natural Gas Delivery System Work?”)
Pipeline pressurization. “Gas flowing from higher to lower pressure is the fundamental principle of the natural gas delivery system,” the website says. “From the gathering system, the natural gas moves into the transmission system, which is composed of about 272,000 miles of high-strength steel pipe ranging from 20 inches to 42 inches in diameter. These large transmission lines for natural gas can be compared to the nation’s interstate highway system for cars. They move large amounts of natural gas thousands of miles from the producing regions to local distribution companies (LDCs). The pressure of gas in each section of line typically ranges from 200 pounds to 1,500 pounds per square inch, depending on the type of area in which the pipeline is operating. As a safety measure, pipelines are designed and constructed to handle much more pressure than is ever actually reached in the system. For example, pipelines in more populated areas operate at less than one-half of their design pressure level.”
“When the natural gas in a transmission pipeline reaches a local gas utility, it normally passes through a ‘gate station,'” the AGA website continues. “Gate stations … reduce the pressure in the line from transmission levels (200 to 1,500 pounds) to distribution levels, which range from ¼ pound to 200 pounds.”
“Natural gas runs from the main into a home or business in what’s called a service line,” the website continues. “Today, this line is likely to be a small-diameter plastic line an inch or less in diameter, with gas flowing at a pressure range of over 60 pounds to as low as ¼ pound… When the gas reaches a customer’s meter, it passes through another regulator to reduce its pressure to under ¼ pound, if this is necessary. (Some services lines carry gas that is already at very low pressure.) This is the normal pressure for natural gas within a household piping system, and is less than the pressure created by a child blowing bubbles through a straw in a glass of milk. When a gas furnace or stove is turned on, the gas pressure is slightly higher than the air pressure, so the gas flows out of the burner and ignites in its familiar clean blue flame.”
Customers involved in the Massachusetts catastrophe, however, describe something far more disturbing than a clean blue flame. “In Lawrence, a man whose neighborhood was among dozens that erupted in fire says he ran into his basement to find that the room was glowing.,” the Boston Globe reported (see: “18-year-old killed as gas explosions and fires destroy homes in Lawrence, Andover, and North Andover,” by Philip Marcelo/AP). “Resident Ra Nam says he was in his yard when the smoke detector in his basement went off around 4:30 p.m. EDT Thursday. When he ran downstairs and saw the boiler on fire, he quickly grabbed a fire extinguisher and put it out. Minutes later, Nam said he heard a loud boom from his neighbor’s house and the ground shook. Nam said a woman and two kids had made it out of the house but the basement was on fire.”
“The rapid-fire series of gas explosions ignited fires in dozens of homes in Lawrence, Andover and North Andover, forcing entire neighborhoods to evacuate as crews scrambled to fight the flames and shut off the gas and electricity,” NECN reported (see: “Officials Work to Pinpoint Cause of Massachusetts Gas Explosions”). “Gas remained shut off Friday in most of the area, and the streets were eerily deserted.”
Frustratingly Few Answers At This Time
Federal investigators are headed to Massachusetts to find out what happened, reported NECN: “The National Transportation Safety Board said it is sending a team to investigate, saying pipelines are within its jurisdiction. NTSB Chairman Robert Sumwalt spoke from Washington, D.C. before leaving for Massachusetts on Friday morning, explaining his agency’s role in the investigation. Typically known for rail or highway investigations, the NTSB has jurisdiction over gas pipelines as well because they are used to transport gas.”
“We will begin putting together our investigative teams and establishing our investigative protocols, looking at the design of the pipeline system and any maintenance and upgrades in the process of being done,” Sumwalt said. “The NTSB’s role is to conduct an accident investigation. We’re there to investigate the accident to determine what happened so we can keep it from happening again.”
On Friday afternoon, the Massachusetts Emergency Management Agency (MEMA) tweeted, “Investigation is in beginning stages, and will be conducted jointly between local, state, federal agencies including @NTSB. At this time, there is no information on cause of yesterday’s gas over-pressurization.” Governor Baker tweeted, “We have brought in and will continue to bring in hundreds of natural gas technicians who will deploy throughout the neighborhoods to do the work they need to do, house by house, to ensure each building is safe to occupy. Once neighborhoods are cleared, the power can be restored. We ask for continued patience as this important work is done. Once utilities secure the affected areas, we will work with the federal government to investigate how this occurred and hold people accountable for their actions.”
Possible precedent. Officials were unwilling to speculate on what might have caused the gas system failure. But a clue might come from a similar incident in the village of Fairport Harbor, Ohio in 2011, where numerous homes caught on fire. An Ohio Public Utilities Commission report is here. Investigators traced the problem in that case to a faulty pressure regulator that had not been regularly cleaned and inspected, as called for by national and state regulations. When fluid contamination in the gas lines collected in the regulator, it stopped working, letting gas at 8 pounds of pressure flow to houses which were supposed to operate on less than a half a pound of pressure. State officials recommended a half-million-dollar penalty for the utility in the Ohio case; given that dozens of houses were damaged in this week’s Massachusetts incident (not to mention the disruption to lives and businesses), that figure is sure to fall far short of the cost of the Massachusetts disaster.
