Skip Ribbon Commands
Skip to main content
Safety Recommendation Details

Safety Recommendation P-18-006
Synopsis: On September 13, 2018, about 4:00 p.m. eastern daylight time, a series of explosions and fires occurred after high-pressure natural gas was released into a low-pressure gas distribution system in the northeast region of the Merrimack Valley, Massachusetts. The distribution system was owned and operated by Columbia Gas of Massachusetts (Columbia Gas), a subsidiary of NiSource, Inc. The system overpressure 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 was a result of structure fires ignited by gas-fueled appliances. Several structures were destroyed by natural gas explosions. One person was killed and at least 21 individuals, including 2 firefighters, were transported to the hospital. Seven other firefighters received minor injuries.
Recommendation: TO NISOURCE: Revise the engineering plan and constructability review process across all of your subsidiaries to ensure that all applicable departments review construction documents for accuracy, completeness, and correctness, and that the documents or plans be sealed by a professional engineer prior to commencing work. (Urgent)
Original recommendation transmittal letter: PDF
Overall Status: Open - Initial Response Received
Mode: Pipeline
Location: Merrimack Valley, MA, United States
Is Reiterated: No
Is Hazmat: No
Accident #: PLD18MR003
Accident Reports: Preliminary Report Pipeline: Over-pressure of a Columbia Gas of Massachusetts Low-pressure Natural Gas Distribution SystemSafety Recommendation Report: Natural Gas Distribution System Project Development and Review (Urgent)
Report #: PSR-18-02
Accident Date: 9/13/2018
Issue Date: 11/15/2018
Date Closed:
Addressee(s) and Addressee Status: NiSource, Inc. (formerly Columbia Gas) (Open - Initial Response Received)

Safety Recommendation History
From: NiSource, Inc. (formerly Columbia Gas)
Date: 12/14/2018
Response: -Joe Hamrock, President and CEO: NiSource will review our Engineering and Construction Gas Standards and our Constructability Review processes and implement changes to ensure that all internal operations departments are required to participate in Constructability Reviews and sign off that all documents used for construction are accurate and complete. NiSource will have a third party firm with gas industry expertise review and validate the above modified engineering and construction standards. All relevant construction documents and plans for construction work that could pose a material risk to public safety will be sealed by a professional engineer prior to commencing construction work. This work would include new or replacement mains involving multiple tie-ins, new or replacement of major components of a point of delivery, district regulator stations or large volume customer measurement and regulation station. For routine main extensions involving a standard tie-in, emergency main replacements requiring standard tie-ins and new and replacement service lines, NiSource will develop standard designs and construction procedures and have them reviewed and approved by a professional engineer.

From: NTSB
To: NiSource, Inc. (formerly Columbia Gas)
Date: 11/15/2018
Response: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to provide assistance to victims and their family members affected by major transportation disasters. On November 14, 2018, the National Transportation Safety Board (NTSB) adopted its safety recommendation report, Natural Gas Distribution System Project Development and Review PSR 18/02. The details of this safety recommendation report may be found at Among the safety recommendations are four urgent safety recommendations issued to NiSource, Inc., which can be found on page 7 of the report. The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 30 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number. We encourage you to submit your response to If it exceeds 10 megabytes, including attachments, please e-mail us at the same address for instructions. Please do not submit both an electronic copy and a hard copy of the same response.