Gas Pipeline Safety in Massachusetts

Gas Infrastructure in Massachusetts

Massachusetts has one of the most scrutinized gas distribution systems in the United States, largely due to the September 2018 Merrimack Valley disaster in which over-pressurized gas lines caused dozens of explosions, fires, and one fatality across Lawrence, Andover, and North Andover. National Grid and Eversource are the state's two dominant gas distributors, serving densely populated communities across eastern Massachusetts. The state has some of the highest concentrations of aging cast iron gas mains in the country, particularly in older urban areas like Boston, Worcester, and Springfield.

Key Risk Factors

Cast iron pipe — brittle, prone to cracking, and incapable of being fused like plastic — remains widespread in Massachusetts cities, and its replacement has been a slow, expensive, and logistically complex undertaking. Pressure regulation failures, like those that triggered the Merrimack Valley disaster, represent a systemic risk in systems where aging infrastructure components interact in unexpected ways during routine maintenance or upgrade work. The density of underground utilities in Massachusetts urban corridors — gas, electric, water, telecom, steam — creates extreme excavation complexity and elevated strike risk during any below-ground work.

Incident Patterns

Massachusetts has a documented history of cast iron main failures, with cold weather exacerbating the brittleness of older pipe materials and driving a winter spike in gas leak reports. The aftermath of the Merrimack Valley disaster led to significantly expanded inspection and replacement programs, but the scale of the state's cast iron inventory means risks remain in areas not yet reached by replacement work. You can explore all incidents in Massachusetts on our site.

Regulatory Oversight

Gas distribution in Massachusetts is regulated by the Massachusetts Department of Public Utilities (DPU), which has significantly increased its pipeline safety oversight since the Merrimack Valley incident. Massachusetts uses the Dig Safe system — call 811 or submit a locate request online at least 72 hours before digging to have buried utilities marked, a legal requirement for any excavation in the state.

Stay Safe

• Learn the signs of a gas leak
• Know what to do if you smell gas
• Understand how gas leak detectors work