Overview:

On September 13, 2018, around 4:00 p.m. EDT, a series of explosions and fires occurred in the Merrimack Valley region of Massachusetts, affecting the communities of Lawrence, Andover, and North Andover. The incident resulted in one fatality, 22 injuries, and damage to 131 structures, including the destruction of at least five homes.

Key Findings:

• The overpressurization of a low-pressure natural gas distribution system caused the incident.

• During pipeline replacement work, a critical pressure sensor was left connected to a decommissioned pipeline, leading to excessive gas pressure in the system.

• The low-pressure distribution system lacked adequate overpressure protection mechanisms.

Lessons Learned:

• Engineering Oversight: Comprehensive planning and review of engineering procedures are essential to prevent critical oversights during maintenance operations.

• System Redundancies: Implementing overpressure protection devices can prevent catastrophic failures in gas distribution systems.

• Training and Procedures: Utility companies must ensure that personnel are adequately trained and that procedures are in place to verify the correct configuration of system components during maintenance.