While leaks are common, disasters involving gas rare in N.H.

  • CDC

  • Massachusetts Gov. Charlie Baker tours 35 Chickering St., where a young man was killed during a gas explosion in Lawrence, Mass. on Thursday. AP

Monitor staff
Published: 9/17/2018 6:23:57 PM

As Massachusetts copes with one of the nation’s worst residential natural gas disasters, New Hampshire can be thankful that even though 120,000 customers have natural gas in the state, it has seen few major accidents and a single fatality over the past three decades.

That doesn’t mean concern never arises, however.

“In the past 12 months, the Concord Fire Department has responded to 23 calls for leaks in natural gas or propane lines throughout the city,” said city fire Chief Daniel Andrus in an email response to the Monitor. There were no major incidents, as calls “range from two cases of a pilot light being out to several instances of construction incidents, where an excavation disrupts a line below ground or a gas line is accidentally severed during interior construction operations. In other instances, there was a report of an odor of gas with no measureable reading on our detection equipment.”

Andrus said that is typical of his experience here.

“We get gas leaks in houses all the time and have monitoring equipment on all of our front-line units to determine if a leak is within ignitable limits,” he said. “I can’t recall any incident in my time where it really progressed substantially.”

Liberty Utilities has about 11,000 gas customers in Concord, out of 92,000 in the state.

Data maintained by the Public Utilities Commissions’ gas division indicates that Liberty Utilities, which provides natural gas throughout the Merrimack Valley from Massachusetts up to Laconia, has seen two major incidents caused by its equipment or service in the past 29 years while Unitil, which provides gas in the Seacoast area, has seen three. They are the only major natural gas or propane companies in New Hampshire.

The fatality occurred in Manchester in March 2009 when a gas leak inside a home caused an explosion, killing an 85-year-old man. According to the state fire marshal’s office, that was caused when a gas pipe inside the house was damaged by the homeowner during outside work. Gas built up in the house unnoticed by the man, who lived alone. Perhaps he didn’t notice because he “used mothballs inside his home and the odor may have prevented him from smelling the gas leak,” according to reports about the investigation.

Major incidents in the PUC database include a house that burned down in Hampton in 2015 after gas leaked from a meter in the foundation; a house that burned in Rochester in 2009 after a meter was damaged while plowing snow; and a couple of incidents of buildings burning after a pipeline was ruptured by excavators, including in 2009 in Laconia.

By far the biggest gas-related emergency in New Hampshire’s recent history didn’t involve an explosion. In December 2015, what was then New Hampshire Gas in Keene – now part of Liberty Utilities – improperly mixed air and propane in a system that provided gas to hundreds of customers. The combination created a dangerously explosive mixture covering buildings in 2 square miles of downtown. Nobody was hurt and the gas was replaced, although some equipment was damaged by the bad mixture.

Last week’s crisis

In Massachusetts, at least 39 homes in Lawrence, Andover and North Andover exploded or burned last Thursday following gas leaks that were apparently caused by failure of one or more regulators, a system that controls and monitors the pressure of natural gas in pipelines. It was an extremely unusual disaster since natural gas fires and explosions almost always are caused by problems with a line or equipment connecting a single building.

Major distribution lines carry gas at a pressure as high as 1,500 pounds per square inch to increase efficiency. The pressure is reduced by regulators to just a few pounds per square inch before it is sent into transmission pipelines under streets that carry gas to homes and offices. A failure of one or more regulators would send high-pressure gas into many of these street pipes, overwhelming the meters in multiple homes.

Amanda Noonan, director of Consumer Services and External Affairs for the New Hampshire Public Utilities Commission, noted that since 2008 the gas safety division of the PUC has imposed a number of requirements that are stricter than federal minimums, including requiring automatic reporting networks to operate on most gas and propane systems.

“Failure in a regulator would be instantly seen and whatever company owns it would respond,” Noonan said.

One concern related to natural gas is the age of systems. Eastern Massachusetts has some of the nation’s oldest pipeline networks.

New Hampshire, like many states, has been overseeing a program of replacing cast iron and bare steel gas and propane pipes, which are prone to failure. Since 1994, according to state data, Liberty Utilities has replaced such pipes serving more than 7,000 customers, although about another 6,000 are still served by cast iron or bare steel pipes. Under current schedules, all those pipes will not be replaced until about 2024.

According to PUC data, of 1,240 miles of Liberty Utility pipeline in New Hampshire, 83 miles  were installed before 1940 and another 390 miles were installed before 1980, while 409 miles, or about one-third of the total, have been installed since the year 2000.

(David Brooks can be reached at 369-3313, dbrooks@cmonitor.com or on Twitter @GraniteGeek.)

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