5,900
natural gas leaks discovered under Washington, D.C.
This
is a map of the District of Columbia showing where researchers found
natural gas leaks under city streets, with colors indicating the
concentration in parts per million of methane at each location.
Credit: Duke University
16
January, 2014
More than 5,893 leaks from aging natural gas pipelines have been found under the streets of Washington, D.C. by a research team from Duke University and Boston University.
A
dozen of the leaks could have posed explosion risks, the researchers
said. Some manholes had methane concentrations as high as 500,000
parts per million of natural gas – about 10 times greater than the
threshold at which explosions can occur.
Four
months after phoning in the leaks to city authorities, the research
team returned and found that nine were still emitting dangerous
levels of methane. "Finding the leaks a second time, four months
after we first reported them, was really surprising," said
Robert B. Jackson, a professor of environmental sciences at Duke who
led the study.
The
researchers published their findings this week in the peer-reviewed
journal Environmental Science & Technology.
"Repairing
these leaks will improve air quality, increase consumer health and
safety, and save money," Jackson said. "Pipeline safety has
been improving over the last two decades. Now is the time to make it
even better."
Nationally,
natural gas pipeline failures cause an average of 17 fatalities, 68
injuries, and $133 million in property damage annually, according to
the U.S. Pipeline and Hazardous Materials Safety Administration.
In
addition to the explosion hazard, natural gas leaks also pose another
threat: Methane, the primary ingredient of natural gas, is a powerful
greenhouse gas that also can catalyze ozone formation. Pipeline leaks
are the largest human-caused source of methane in the United States
and contribute to $3 billion of lost and unaccounted for natural gas
each year.
This
is a satellite image of the District of Colombia with bar charts
showing where natural gas leaks were located under city streets and
in what concentration methane was identified. Higher bars indicate
higher concentrations in parts per million. Credit: Duke University
Jackson's
team collaborated with researchers from Boston University and Gas
Safety, Inc., on the new study. The team mapped gas leaks under all
1,500 road miles within Washington using a high-precision Picarro
G2301 Cavity Ring-Down Spectrometer installed in a GPS-equipped car.
Laboratory analyses then confirmed that the isotopic chemical
signatures of the methane and ethane found in the survey closely
matched that of pipeline gas.
The
average methane concentration observed in the leaks was about 2.5
times higher than in background air samples collected in the city.
Methane levels in some leaks were as high as 89 parts per million,
about 45 times higher than normal background levels.
The
team also measured how much methane was coming from four individual
street-level leaks. "Methane emissions from these four leaks
ranged from 9,200 to 38,200 liters per day for each leak—that's
comparable to the amount of natural gas used by between 2 and 7
homes," said Duke Ph.D. student Adrian Down.
Last
year, the team mapped more than 3,300 natural-gas pipeline leaks
beneath 785 road miles in the city of Boston. "The average
density of leaks we mapped in the two cities is comparable, but the
average methane concentrations are higher in Washington," said
Nathan G. Phillips, a professor at Boston University's Department of
Earth and Environment.
Like
Washington and Boston, many U.S. cities have aging pipeline
infrastructure that may be prone to leaks. The researchers recommend
coordinated gas-leak mapping campaigns in cities where the
infrastructure is deemed to be at risk.
The
new study comes at a time when the nation's aging pipeline
infrastructure is generating increased legislative attention. Last
November, Sen. Edward J. Markey (D-Mass.) introduced two new bills to
speed up the replacement of natural gas pipelines in states with
older infrastructures by offering new federal programs and incentives
to help defray the costs associated with the repairs.
"We
need to put the right financial incentives in place," said
Jackson. "Companies and public utility commissions need help to
fix leaks and replace old cast iron pipes more quickly."
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