The city of Boston’s aging urban natural gas pipeline infrastructure is rife with leaks, according to a new study by researchers working together from Boston and Duke universities.

The researchers said they identified a total of 3,356 methane leaks across all 785 roads in Boston. Most of the leaks are tiny, but six locations had gas levels higher than the threshold at which explosions could occur, The Boston Globe reported.

“These leaks don’t pose risks and are monitored regularly by the utilities,” a spokeswoman for the Massachusetts Department of Public Utilities told NGI. “Any leaks that pose risks are fixed immediately.” National Grid is the predominant gas distributor in the Boston area, she noted.

The study, “Mapping Urban Pipeline Leaks: Methane Leaks Across Boston,” comes only weeks after Superstorm Sandy slammed into the Northeast, further damaging aging gas distribution systems and causing fires fueled in part by escaping gas.

However, primarily “the leak prevalence is associated with old cast iron pipes across 10 Boston neighborhoods,” according to the authors, whose study was published last week in the online edition of the peer-reviewed journal Environmental Pollution.

Cast and wrought iron pipelines are among the oldest energy pipelines constructed in the United States. Many of these pipelines were installed more than 60 years ago and still deliver natural gas to homes and businesses. However, the degrading nature of iron alloys, the age of the pipelines, and pipe joints design have greatly increased the risk involved with continued use of such pipelines, said the Department of Transportation’s (DOT) Pipeline and Hazardous Materials Administration (PHMSA).

DOT Secretary Ray LaHood issued a Call to Action in March 2011 urging states to promote pipeline safety awareness and pipeline operators to accelerate efforts to repair, rehabilitate, and replace higher-risk pipeline infrastructure – including cast iron pipelines, which have been at the heart of several tragic incidents that caused injuries and claimed lives. In January, President Obama signed the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011, which called for the DOT to conduct a state-by-state survey on the progress of cast iron pipeline replacement (see NGI, Jan. 9).

The amount of cast and wrought iron pipeline in use has declined significantly in recent years due to increased state and federal safety initiatives and pipeline operators’ replacement efforts. Some states have completely eliminated cast or wrought iron natural gas distribution lines within their borders, including Alaska, Arizona, Hawaii, Idaho, Montana, North Dakota, New Mexico, Nevada, Oregon, South Carolina, Utah, Vermont, Wisconsin and Wyoming.

Almost all (97%) of natural gas distribution pipelines in the United States at the end of 2011 were made of plastic or steel. The remaining pipes mostly are made of iron.

Despite the movement away from cast iron pipeline, there were 31 serious accidents on gas distribution facilities in 2011, resulting in 11 deaths and 52 injuries, according to the PHMSA. Property damages totaled $5.5 million. So far this year the number of reported deaths on distribution facilities is lower (six), and injuries are 19, the agency said. Property damages have been estimated at $4.3 million.

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