BOSTON — Utilities are under growing pressure from lawmakers and environmental groups to plug tens of thousands of leaks in aging underground gas pipelines, some of which are decades old.

An interactive map of leaks throughout the state posted by a Cambridge nonprofit group, the Home Energy Efficiency Team, pinpoints tends of thousands of leaks, some of them major. The map uses data provided by National Grid, Eversource, Columbia Gas and other providers.

A law passed last year requires the utilities to track and grade all gas leaks on a scale of 1 to 3, with 1 being most serious, and immediately repair the most hazardous. The law also requires utilities to share the information with the public.

The law's primary sponsor, Rep. Lori Ehrlich, D-Marblehead, noted that utilities aren't required to fix lesser "grade 3" leaks adjacent to buildings, which account for more than 95 percent of the leaks statewide.

A Harvard University study released earlier this year estimated the natural gas bleeding from those pipes and loose connections is costing the state's publicly regulated utilities more than $90 million a year — a cost that is borne by ratepayers.

Ehrlich said the utilities aren't moving quickly enough to fix the leaks and upgrade aging infrastructure.

She has filed new legislation — backed by dozens of lawmakers including Sen. Barbara L'Italien, D-Andover — that requires utilities to fix un-repaired leaks during road construction and that prevents them from passing the bulk of the costs to ratepayers.

Any costs passed onto consumers would be phased in over the next five years.

"Because utility companies are currently allowed to pass the cost of leaking gas onto us, the ratepayers, they have a financial disincentive to fix leaks," Ehrlich said. "My legislation would incentivize them to fix them in a timely manner."

The interactive map — posted at — allows viewers to search for leaks by town and zoom-in on neighborhoods. A quick glance reveals the sheer volume of unplugged leaks. The severity of the leaks is not indicated.

For example, Andover has 86 unprepared leaks, some dating back to 2006. Methuen has had 91 leaks dating back to 2007, while Lawrence has had 171 leaks as far back as 2006.

Gloucester has had 39 leaks back to 1991, and Salem has had 92 leaks dating back to 1991.

Marblehead — which is only 2 1/2 square miles wide, has had 173 leaks, the oldest from 1991.

National Grid is working to fix thousands of smaller "grade 3" leaks. It is upgrading its infrastructure by replacing old iron and steel pipes with newer plastic pipe, which is less prone to leaking, according to a company spokeswoman.

"We believe the best strategy for reducing leaks is to replace older natural gas infrastructure, which is why we have accelerated our main replacement at least fivefold over the past 10 years," said spokeswoman Danielle Williamson.

In an interview with The Salem News earlier this month, Williamson said the number of leaks in Salem had been reduced to 60 after half a year of work.

Besides aging pipes, leaks are caused by freezing conditions and contractors digging up pipelines, she said.

The utility immediately fixes grade 1 leaks but is required to get local permits and other authorization to repair grade 2 and 3 leaks, which slows the process, she said.

National Grid has more than 11,000 miles of natural gas pipeline throughout the state, she said. At least one-third of it is "leak prone" and slated for replacement.

Cost is a factor in how quickly old pipes are upgraded. Replacing one mile of pipe runs between $1.5 million and $2.5 million, she said.

National Grid is required to report the locations of gas leaks every three months to the state Department of Public Utilities. As of Sept. 30, it had 12,878 leaks in Massachusetts, most of them grade 3.

Williamson said she expects the next report, due Dec. 31, to show a "dramatic reduction."

Environmental groups are equally frustrated with the slow pace of stopping the leaks.

Caitlin Peale-Sloan, an attorney with the Conservation Law Foundation, said the state shouldn't be weighing new natural gas pipelines such as one proposed by Texas-based Kinder Morgan until all the leaks are fixed.

"We need to repair our existing infrastructure before we go building new pipelines," she said.

Methane from leaking pipes contributes to greenhouse gas emissions and complicates the state's efforts to meet ambitious benchmarks to reduce its overall carbon footprint by 20 percent by 2020, she said.

The state currently does not account for leaking gas lines in its annual carbon emissions report.

"Methane is an extremely potent greenhouse gas," Peale-Sloan said. "And leaking natural gas is a serious issue, not just for the safety of residents and our pocketbooks, but our ability to reduce greenhouse gas emissions in the state."

Christian Wade covers the Massachusetts Statehouse for CNHI's newspapers and websites. Reach him at

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