On September 13, 2018, excessive pressure in natural gas lines owned by Columbia Gas of Massachusetts caused a series of explosions and fires to occur in as many as 40 homes, with over 80 individual fires, in the towns of Lawrence, Andover, and North Andover, all within the Merrimack Valley, in Massachusetts, United States. One person, 18 year old Leonel Rondon, was killed and 30,000 were forced to evacuate their homes immediately.
Background
According to the NTSB's preliminary report, customers in the accident area received gas from a low-pressure (0.5 psi) distribution network which, in turn, was fed from a high-pressure (75 psi) main pipeline via regulators controlled by sensors measuring pressure in the low-pressure pipes. At the time of the accident, workers were replacing some of the low-pressure piping, but the procedure set out by Columbia Gas for doing this failed to include transfer of a regulator's pressure sensor from the old, disused piping to the new. As a result, when the old pipe was depressurized, the regulator sensed zero pressure on the low-pressure side and opened completely, feeding the main pipeline's full pressure into the local distribution network.
Fires and explosions
The faulty procedure used caused natural gas to build up in homes within a matter of minutes. Multiple explosions and fires were reported over a very short period of time in the towns of Lawrence, Andover, and North Andover beginning about 4:15pm (EDT). Through the evening emergency crews responded to between 40 and 80 fires. At one time, as many as 18 fires were burning at once, and Andover officials struck a maximum 10-alarm response.
Andover's fire chief described "billows of smoke coming from Lawrence behind me, I could see plumes of smoke in front of me within the town of Andover, it just looked like an absolute war zone." A Lawrence resident described finding his boiler on fire after his smoke alarm went off; as he was extinguishing it he heard a boom from a neighbor's house and the ground shook. An explosion at one of the homes involved caused the house to shift off of its foundation. This in turn caused the chimney attached to fall on a car occupied by a fleeing resident, killing him. In addition to this death, twenty-five others were reported injured overall from the whole event. All of the fires were put out by 6:45pm.
Once it was realized that the fires were being caused by over-pressurized gas mains, all residents in South Lawrence, and residents supplied by Columbia Gas in the area were told to evacuate their homes. Foul play was also ruled out as a possible cause by police. Gas service for approximately 8,000 residents was ultimately shut off; electricity to portions of the three communities was also interrupted to avoid igniting any lingering gas.
Response
Thousands of people were told to shut off their gas service and evacuate their homes. In Lawrence, Mayor Dan Rivera urged residents in the city to move north of the Merrimack River. Schools and senior citizen centers were opened up in all three areas to take in the evacuees, and hotels offered shelter as well. The number of people evacuating by vehicle soon caused gridlock on streets that were already experiencing congestion by the afternoon rush hour commute. Portions of Interstate 93 and Interstate 495 were closed to traffic by the Massachusetts State Police and local highways such as Route 125 were temporarily converted to one-way traffic in order to accommodate fleeing residents as well as prevent others from returning to their homes. Merrimack College evacuated its buildings temporarily. Schools and state offices in the three communities remained closed the following day. First responders from as far away as Boston and Manchester, New Hampshire, rushed to Lawrence, Andover, and North Andover as gas and electric lines were shut off to prevent further explosions.
The NTSB also sent a team to investigate the situation the following day stating that they were going to look at the design of the pipeline system, maintenance associated with it, the emergency response, and the integrity management system of Columbia Gas. The gas company involved released several updates about the fires and explosions through their website. The updates expressed sympathy over the "tragic incident" and the resulting death, as well as directing readers to shelters, and how to remain safe throughout the incident. Governor Baker and Lawrence mayor Dan Rivera were later heavily critical of the response issued by Columbia Gas.