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Washington, D.C. is a pretty old city by American standards. It dates back to the late 18th century. Despite frequent facelifts, parts of it are wearing out - for example, its underground gas pipelines.
NPR's Christopher Joyce reports on new research that reveals thousands of natural gas leaks in the nation's capital.
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CHRISTOPHER JOYCE, BYLINE: Washington, D.C. is a city in a constant state of reconstruction. That includes the streets, like the one I'm standing on, First Street Northeast, about a mile from the Capitol. Two blocks of asphalt have been opened up like a gutted fish. Somewhere in there, a gas pipeline has been leaking. It turns out a lot of old gas lines have been leaking here. Washington, as scientists have just discovered, is a pretty gassy city. And here's how the scientists found that out.
ROBERT JACKSON: We drove 1,500 road miles in Washington, D.C. and found about 6,000 leaks. That's roughly four leaks every mile.
JOYCE: Robert Jackson is an environmental scientist at Duke University. Four leaks a mile is even more than this team found in Boston, where they did the same thing - drive the streets with a special instrument that detects methane, that's natural gas. In fact, the average amount of gas lost to leaks in Washington is over twice the national average for cities. And not only were there more leaks...
JACKSON: But in Washington, D.C., the leaks were higher concentrations than anything we saw in Boston in a lot of cases.
JOYCE: In 12 cases, the gas concentration was potentially explosive. Jackson says he informed the local gas company about those early last year.
JACKSON: The really surprising thing was, when we went back four months later - after calling these leaks in - nine of the 12 hadn't been fixed. And that really shocked me.
JOYCE: The city's gas company, Washington Gas Light Company, declined an interview request about this study, which appears in the journal Environmental Science and Technology. In a written response, the company said it, quote, "immediately responds to every report of natural gas odor and repairs leaks seven days a week, 24 hours a day, 365 days a year."
Jackson notes that leaks can be hard to trace. Sometimes whole blocks have to be investigated to find one leak. Also, one-third of Washington's gas mains are cast iron, old technology that's prone to leaks. Washington Gas is replacing many of these. But plugging leaks is like plugging holes in a dike.
DOUG JOHNSON: We have been plagued by a series of ongoing gas leaks.
JOYCE: Doug Johnson lives in an old neighborhood of Washington. Like much of the city, though, there's remodeling going on, lots of new construction and truck traffic. Johnson says gas company workers return over and over to fix leaks on his block. He always asks the foreman, what's going on?
JOHNSON: Basically these streets weren't really built to handle the large construction, the cranes. And he says, look, you know, the pipes are old, they're being put under enormous stress, that probably is your answer right there.
JOYCE: Besides the inconvenience and the cost, methane leaks contribute to global warming. Duke's Jackson is one of many scientists measuring how much comes from cities, industry, farms - wherever. But it's been hard to get consistent numbers.
JACKSON: The scientific community is still trying to figure out, you know, why those differences occur, and what the differences are in practices that might explain them.
JOYCE: Even within Washington, there was a lot of variation. One area that turned out to be fairly gas-free was the National Mall, with the White House at one end and Congress at the other. Science is full of surprises.
Christopher Joyce, NPR News.