The thousands of active gas leaks in the city of Boston were again on the table at a City Council hearing Tuesday afternoon as experts and residents weighed in on an ordinance proposed by City Councillor Matt O’Malley that seeks to eliminate the leaks.

O’Malley and City Councillor At-Large Michael Flaherty co-chaired the Committee on Government Operations hearing, which included over two hours of testimony on the impact and spread of gas leaks in Boston. Representatives from National Grid and Eversource testified at the session.

“This is a significant issue,” O’Malley said. “Even the most conservative estimates peg the number of gas leaks in the city of Boston at close to 2,000. Other independent audits have shown that number is closer to double or perhaps triple that number.”

Gas companies pegged the number closer to 1,300 leaks. Some leaks go unaddressed for decades, he said. One in City Councillor Josh Zakim’s district marked 30 years of neglect last year.

“[Advocacy group] Mothers Out Front brought a cake; they did not light the candles for obvious reasons,” O’Malley said to chuckles from the gallery.

Along with Zakim, O’Malley submitted two resolutions in 2014 that support gas leak prevention measures introduced in the Legislature House by state Rep. Lori Erlich (D-Marblehead) and state Sen. Jamie Eldridge (D-Acton). The resolutions passed unanimously in the council, after which a working group was convened and hearings began taking place on the proliferation of leaks throughout the city.

Last year, National Grid reported 508 unrepaired gas leaks in Dorchester, which has far outpaced the rest of the city in active leaks. A 2014 gas explosion destroyed a home on Hansborough Street, injuring 12 people, a dramatic late-night example of the dangers of unaddressed leaks.

O’Malley’s ordinance seeks to eliminate the leaks in six years, more clearly prioritizing them and scheduling repair work. Utility companies and city agencies like public works, police, and fire would be expected to coordinate reports on leaks, including using existing road work schedules to repair them.

Utility companies would also face fines if gas leaks recur within 5 years after repair or replacement. Additional fines could be levied if the companies do not report a known leak.

Mechanisms in place to deal with gas leaks depend on the their classifications. Grade 1 is immediately hazardous, Grade 2 is potentially hazardous, and Grade 3 comprises the bulk of the problem sites. They are considered minor, posing little or no immediate threat.

Margaret Hendrick, a PhD student at Boston University, spoke on the results of a research paper published this year along with BU professor Nathan Phillips, whose team detected 3,300 gas leaks in the city in 2012. They took measurements from over 100 sites of leak-prone cast iron pipe across Greater Boston. Cast iron pipe makes up about a third of the gas distribution infrastructure across the commonwealth, Hendrick said.

The team found “a preponderance of small gas leaks and a few very large gas leaks,” she said. “These few large leaks contribute disproportionately to overall methane emissions and are considered “super-emitters,” she added. Around 7 percent of the gas leaks surveyed accounted for 50 percent of methane emissions in the Greater Boston area, she noted.

The financial component for ratepayers is also compelling, O’Malley said. A Harvard-led study of gas pipeline infrastructure in Greater Boston determined last January that consumers are paying for more than $90 million in natural gas – enough to fuel 200,000 homes – that is lost each year across the Greater Boston system.

Joel Wool, a Dorchester resident and employee of Clean Water Action, has dedicated years to studying gas leaks, which he said was a matter of “great public interest.” The proposed ordinance would align with measures on Beacon Hill, he said.

“The Massachusetts House had taken very strong action,” he said. “The state Senate has a somewhat simpler amendment that deals with the environmental impact of the non hazardous leaks. But both chambers have acted. They did so in bipartisan fashion... So your continued devotion to these policy changes is having an impact and we are joined by many across the state.”