Engineering Ethics Blog: The Massachusetts Gas Disaster


Being
one of the longest-settled regions of the U. S., the Commonwealth of
Massachusetts has been home to gas utility companies for close to a century and
a half.  Unfortunately, some of the pipes
installed in the 19th century are still in use in older parts of the state,
notably around Lawrence, Andover, and North Andover in the Merrimack Valley
north of Boston.  So earlier this month,
Columbia Gas of Massachusetts, the gas utility serving the area, announced that
it was going to start replacing some older gas lines. 

On
Thursday afternoon, Sept. 13, residents of these towns would have been
justified in thinking that they had suddenly been transported into the midst of
a bad horror movie.  House after house exploded
and caught fire.  The Massachusetts State
Police logged over 30 calls reporting fires, and by Saturday authorities
counted over 60 suspected gas fires in the area.  When one house exploded, its chimney toppled
over onto a car, and one teenager in the car later died of his injuries.  Twenty-five people suffered injuries, some
serious.

As
soon as the scope of the disaster was known, authorities shut off gas and
electric utilities to the areas affected and ordered an evacuation, which
lasted in some cases until Saturday. 
Citing Columbia Gas’s lack of cooperation, Massachusetts Governor
Charlie Baker said he was replacing Columbia Gas with another utility,
Eversource, to lead recovery efforts, and declared a state of emergency in the
region. 

A
thorough understanding of what went wrong in Lawrence will have to wait for the
results of investigations by local, state, and Federal officials, including members
of a National Transportation Safety Board team that were dispatched to the
scene.  Nevertheless, similar incidents
have happened before, and their history is better known.

In
the early days of gas utilities, gas was manufactured typically by the destructive
distillation of coal and stored in large accumulator tanks at close to
atmospheric pressure.  Only enough
pressure to send it through distribution pipes and gas meters was used, and the
delivered pressure was so low it was measured in inches of water, rather than
pounds per square inch (PSI).  About 7
inches of water was the standard delivery pressure then, and it remains so
today—equivalent to about 0.25 PSI.  Such
a low pressure reduces requirements on residential piping and means that even a
wide-open pipe is not going to leak enough gas to form anything more than a
moderate flame.  I have seen a gas
utility worker at a work site in my neighborhood street leave a delivery pipe
open and unattended for a few minutes, with no apparent concern.

But
by the same token, systems designed for such low pressure behave badly if by
some mishap a higher transmission-line pressure reaches them.  For transmission over long distances,
pressures ranging in the 50 to 100 PSI range are used to deliver gas to
substations, where pressure regulators lower the pressure to the low levels
needed at customers’ houses. 

Experts
agree that somehow, a pressure greatly in excess of the normal 0.25 PSI was
mistakenly connected to the distribution system in Andover, North Andover, and
Lawrence.  The exact effects on each home
depended on what kind of appliances were connected and operating at the
time.  Fortunately, the weather was
mild—highs in the 70s, lows in the 60s—so probably few domestic heating systems
were being used.  Still, older furnaces
and stoves use pilot lights, and one official was quoted as saying with enough
pressure, a pilot light can turn into a torch. 
Minor flaws in piping that would withstand 0.25 PSI may give way under higher
pressures, resulting in major leaks of gas that can be triggered by an electric
spark, a burning candle, or other source of ignition.  Out of the many hundreds of homes serviced by
Columbia Gas in that region, some 60 or so suffered either major leaks or fires
and explosions as a result.

When
I lived in Massachusetts for a time after growing up in Texas, I noticed a
rather widespread prejudice against gas for domestic heating, as opposed to
either electricity or heating oil.  I
encountered more than one person who said they would never buy or rent a place
with gas, simply because of the danger. 
Having grown up in a house heated with gas floor furnaces and space
heaters (most of which would be too dangerous to install in new construction
today), this attitude struck me as strange. 
But Columbia Gas has not done its industry’s reputation any good by
first allowing this accident to happen, and then by failing to take quick,
decisive public actions to mitigate the disaster.  Columbia Gas’s parent company NISource saw
its stock price fall 12 percent on the Friday following the disaster, an
unusual occurrence for a generally conservative investment such as a
fully-regulated utility firm. 

Environmentally
speaking, the use of natural gas for domestic heating is more efficient than
electric heating, even if natural gas is used to power the electric generation
plants.  It can be argued that in making
so many new natural-gas discoveries over the past decade, the U. S. has done
more in recent years to replace higher-carbon-emission oil with natural gas
than any other nation, thus decreasing the world’s carbon footprint. 

But
these arguments will not console those who have lost loved ones or property in
the Massachusetts gas explosions.  I
wouldn’t blame them if some of them return to what is left of their homes and
rip out all the gas lines completely.  I
can also imagine the troops of lawyers who must be descending upon the region
to file lawsuits against Columbia Gas and anyone else with deep pockets who
might have been involved.  There is
justice in compensating victims for their losses to the extent possible.  A trust has been betrayed when a utility’s
normally benign facilities suddenly turn into engines of fire and
destruction.  It will be interesting to
learn what combination of mechanical failure, lack of understanding, and
management errors led to this tragedy. 
But even if we learn everything there is to know, that won’t fix the
death and damage that resulted from it. 



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