Twelve people were injured when a gas leak explosion destroyed this home at 27 Hansborough Street in April 2014. Photo courtesy Boston Fire Dept.
When a duplex on Dorchester’s Hansborough Street exploded on a chilly April night last year, the entire block shook. Twelve people were injured, two critically. Neighbors were evacuated as fire consumed the house behind them; they stood on the sidewalks, clutching blankets, and each other.

The cause was determined to be a gas leak, one of the thousands that spill out across Boston each year. Dorchester has 570 unrepaired leaks, according to the Home Energy Efficiency Team (HEET), making it far and away the neighborhood containing the most of Boston’s 1,757 gas leaks. Last January, a Harvard-led study of gas pipeline infrastructure in Greater Boston determined that consumers are paying for more than $90 million in natural gas that is lost each year across the Greater Boston system, enough to fuel 200,000 homes.

Boston is riddled for the most part with tiny leaks, few of which pose any danger of explosion, but the toll that natural gas seepage takes on the environment and customers’ wallets is not insubstantial, experts say. “We’ve all smelled it, wondered how dangerous it can be,” said City Councillor Matt O’Malley at a hearing that he and Councillor Josh Zakim convened on the subject on Monday night.

Though numbers dwindled by the end of the hearing, which lasted more than three hours, the council chambers were full as a series of panelists begin to speak about the problem. “Fix the leaks first, and fix the leaks fast,” said Claire Humphrey from Jamaica Plain, who was testifying on behalf of Mothers Out Front, a coalition of mothers, grandmothers, and other caretakers who mobilize for climate and energy action.

Members of the group were out in force at the hearing, many holding and handing out colorful signs by neighborhood detailing the number of gas leaks in each one.

As a mother, Humphrey said, she was particularly distressed by the lack of speed in repairing gas leaks. “We are not addressing one of the biggest threats to their health and their future out there,” she said, indicating her two children in the audience.

Some of the city’s aging and degrading metal pipes are more than 50 years old, slated for replacement or repair based on their condition and location. Of the currently tracked and reported gas leaks, Boston has 36 at Grade 1 (hazardous), 157 at Grade 2 (potentially hazardous), and 1,554 at Grade 3. The Grade 3 leaks make up the bulk of the city’s leaks; they are considered minor, posing little or no immediate threat.

State Rep. Lori Erlich (D-Marblehead) championed legislation signed into law in July 2014 aimed at speeding repairs of natural gas leaks.
The legislation set standards for leak classification and put grades 1 and 2 leaks on a repair timeline. Gas companies are also required to deliver leak information to municipal and public safety officials upon request, and must report to the Legislature any backlog of repairs and an estimate of leaked methane emissions.

Erlich and state Sen. Jamie Eldridge (D-Acton) spoke on a panel regarding legislative efforts to further their efforts. At the hearing Erlich said she was pleased by much of the law’s work, but remained frustrated that it did not address Grade 3 Leaks.

“Boston has the second oldest gas delivery system in the country and the highest per capita use of cast iron [pipes],” she said, listing a litany of known gas leaks within a few blocks. The city’s oldest known leak, almost 30 years old, remains at the corner of Park Drive and Beacon Street. “You get the idea,” she said. “They’re everywhere.”

Among other additions, Erlich wanted precise regulations in place regarding immediate leak repair near schools, a proposal complicated by Boston’s high volume of educational facilities. They are surveyed regularly, she said, but “much squishier language did prevail.”

Monday’s hearing was a step toward addressing gas leaks within the city, O’Malley said. Questions were raised on coordination between city public works departments and utilities to repair leaks, and the timeline for repairing them in the long-term.

O’Malley credited National Grid for sending representatives to discuss the problem, which he said indicates a willingness by the utility to work with the city and its residents. The company provides gas to 90 percent of Boston consumers.

Susan Fleck, vice president of gas pipeline safety and compliance at National Grid, said that of the 420 miles of leak- prone pipe in Boston – out of slightly more than 800 miles of pipe in the city overall – they are able to replace 20 to 25 miles per year. They also try to repair pipes that will need to last for longer stretches of time before replacement, electing not to repair most leaks on pipes that are slated to be replaced. That 30-year leaking pipe at Park Drive and Beacon is not going to be replaced until 2018, she said.
Lost or unaccounted-for gas represents only half a percent of gas flow, she said, calling the amount a “grossly misunderstood concept.” National Grid’s rate of pipe replacement has increased by a factor of 10 in recent years, she said, and repairing and replacing pipes is a “very significant investment” on the part of the company.

The small leaks add up over time, panelists said. Some, including Zakim, spoke passionately on behalf of trees dying from gas leaking into the soil. Methane, the main component to natural gas, is a greenhouse gas that traps heat and is about 25 times more potent than carbon dioxide. When it enters the soil and cuts off oxygen to tree roots, the trees die and must be removed.

“It’s common practice for gas companies to list dead and dying plants as an indicator of gas leak activity,” said Boston University professor Nathan Phillips, whose team detected 3,300 gas leaks in the city in 2012.

Ann Stillman, of Jamaica Plain, mourned trees that slowly withered because of an undetected natural gas leak near her home. When she called the utilities, she said, the leak was discovered and repaired, “but nothing else happened, and the tree, the beautiful tree in front of our house, continued to die.”