Final Report: 'Weak Engineering Management' Led To Gas Explosions

ANDOVER, MA — The Sept. 13, 2018 natural gas line explosions that killed one, injured 22 and damaged 131 structures in the Merrimack Valley were caused by "weak engineering management" on the part of Columbia Gas of Massachusetts, a unit of NiSource, according to the National Transportation Safety Board's final report. According to the report, a crucial step in the abandonment of an old cast iron gas line was skipped, resulting in misreadings of gas pressure and thus the release of high pressure gas into a low pressure system, which could not handle the pressure. That step was skipped due to "inadequate planning, documentation and record-keeping," the investigators found.

The key accident omission occurred near the intersection of South Union and Salem Streets in Lawrence. A crew was replacing an older, low-pressure cast-iron gas pipe that had been installed in the early 1900s with a new plastic line. The sensors that should have sensed the increased pressure remained on the older, abandoned line. As the pressure dropped in that line, they automatically increased pressure to the low-pressure system, overloading it.

The report also explicitly rebuts NiSource's prior claim that a one and a half year delay on the part of the city of Lawrence was a contributing factor. "A delay in construction does not justify a catastrophic accident," the report reads.

The board found that if the company had conducted a comprehensive risk assessment, they would have known that a system like theirs could lead to an accident of this sort. "They would have identified the human error," they wrote.

The report also critiques the emergency management response, which it attributes to non-interoperability of different departments' and towns' emergency responders, as well as Columbia Gas not being adequately prepared to help emergency management. The communication issues "illustrate the need for emergency planning for a multi-jurisdictional response," they said.

Because public officials were working without accurate information, the board found that they "evacuated and shut down electricity in an area larger than necessary."

As part of the report, the board made a number of new safety recommendations, to both government agencies and NiSource. They recommended that NiSource review its protocols and training on responding to large scale emergencies and that Massachusetts develop guidance on communications during multi-jurisdictional emergency response. They also recommended that the federal Pipeline and Hazardous Materials Safety Administration alert all operators of low-pressure natural gas systems of the risk of a Merrimack Valley-type system failure.

The explosions killed one person, 18-year-old Lionel Rendon of Lawrence. In the aftermath of the explosions, many residents were unable to return to their homes for months.

In May, NiSource announced a settlement with the three towns, Andover, North Andover and Lawrence, of up to $80 million for repairs, expenses, and claims and losses incurred by the three communities.

Since the explosions, the Massachusetts Department of Public Utilities has issued a dozen sets of orders to the company, most recently imposing a moratorium on all non-emergency work in the state after a gas leak in Lawrence last month. The department found issues in the company's abandonment of old lines, as part of restoration work, and demanded that they check hundreds of abandoned lines across the three municipalities.

The board is holding a community outreach event Friday, Oct. 25 at 3 p.m. at the Lawrence Public Library, to update the public on the investigation.