In an effort to combat the thousands of gas leaks in Boston, City Councillor Matt O’Malley held the first of at least two working sessions on the topic Thursday, at the end of which he hopes to present a concrete piece of legislation.

The primary focus of the legislation would be a comprehensive plan to assess the severity and priority of leaks and coordination between utility companies and city departments on a schedule of repairs.

The city is “seeing how immediate the impact is,” and consumers are paying an estimated $90 million in unaccounted-for gas, O’Malley said. Apart from the danger to residents, there are a slew of damaging environmental and economic effects of continuous gas leaks.

O’Malley and councillor Josh Zakim convened the session under the committee of environment and parks. At-large councillor Michelle Wu attended, as did representatives from other councillor’s offices.

National Grid director Joe Carroll and community and customer manager Peter Nagle participated in the session, which O’Malley said was an encouraging sign that the utility company was willing to work with the city. National Grid supplies 95 percent of the City of Boston’s gas, according to O’Malley.

Discussion revolved around the speed of gas leak repairs and pipe replacement. Katie Choe with Public Works said there are about 400 miles of pipe to be replaced in the City of Boston, which has about 800 miles total. National Grid replaces about 25 miles of pipe a year, at which rate O’Malley pointed out would take about 17 years to complete, notwithstanding new leaks.

The oldest known gas leak in the city, at intersection of Beacon Street and Park Drive near Kenmore Square, was just fixed, after more than 30 years as a Grade 3 low-level leak. However, the number of Grade 3 leaks in the city hovers somewhere between 1,300 and 1,600, those at the session estimated.

Some at the session had testified in favor of House Bills 2870 and 2871, sponsored by State Rep. Lori Erlich (D-Marblehead) and State Sen. Jamie Eldridge (D-Acton). The bills, respectively, would protect consumers from being charged for undelivered gas and codify coordination between the city and town and utility companies to repair existing leaks and replace pipe.

Joel Wool, of Clean Water Action, suggested that National Grid engage in the “benevolent practice” of mapping active gas leaks for transparency and safety reasons, as a number of other utilities do. Looking ahead at potential legislation, Wool recommended incorporating measurements for lost gas, coordination strategies between city and utility, and the mapping system.

O’Malley plans to call at least one other work session on the subject after the holidays.