In This Issue

NTSB Issues Findings and Recommendations from Merrimack Valley Incident

The National Transportation Safety Board (NTSB) conducted a public meeting on September 24th and issued their findings and recommendations related to the Columbia Gas of Massachusetts’ overpressurization incident. The incident that occurred on September 13, 2018 involved high-pressure natural gas accidentally released into a low-pressure gas distribution system in the northeast region of the Merrimack Valley. One person was killed and 22 individuals, including three firefighters, were transported to local hospitals due to injuries. The fires and explosions damaged 131 structures, including at least 5 homes that were destroyed in the city of Lawrence and the towns of Andover and North Andover. Most of the damage occurred from fires ignited by natural gas-fueled appliances; several of the homes were destroyed by natural gas-fueled explosions.

  • An abstract of the final report, which includes the findings, probable cause, and all safety recommendations, is available here.
  • The urgent safety recommendations issued earlier in the investigation are available here.

NTSB Recommendations:


  1. Revise Title 49 Code of Federal Regulations Part 192 to require overpressure protection for low-pressure natural gas distribution systems that cannot be defeated by a single operator error or equipment failure.
  2. Issue an alert to all low-pressure natural gas distribution system operators of the possibility of a failure of overpressure protection; and the alert should recommend that operators use a failure modes and effects analysis or equivalent structured and systematic method to identify potential failures and take action to mitigate those identified failures.

To the States of Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Illinois, Iowa, Kentucky, Louisiana, Maine, Maryland, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New York, North Carolina, Pennsylvania, South Carolina, South Dakota, Texas, Utah, Virginia, and Wyoming:

  1. Remove the exemption so that all future natural gas infrastructure projects require licensed professional engineer approval and stamping.

To the Commonwealth of Massachusetts Executive Office of Public Safety and Security:

  1. Develop guidance that includes a component for effective communications when deploying mutual aid resources within the first hours of a multi-jurisdictional incident.

To NiSource, Inc.:

  1. Review your protocols and training for responding to large-scale emergency events, including providing timely information to emergency responders, appropriately assigning NiSource emergency response duties, performing multi-jurisdictional training exercises, and participating cooperatively with municipal emergency management agencies.