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Safety Recommendation Details

Safety Recommendation P-18-009
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: Develop and implement control procedures during modifications to gas mains to mitigate the risks identified during management of change operations. Gas main pressures should be continually monitored during these modifications and assets should be placed at critical locations to immediately shut down the system if abnormal operations are detected. (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: As previously announced, NiSource will be installing automatic pressure control equipment, referred to as “slam-shut” devices, on every low-pressure system across our seven-state operating area. These devices provide another level of control and protection, in that when they sense operating pressure that is too high or too low, they immediately shut down gas to the system. As an additional layer of protection, NiSource will install remote monitoring devices on all low-pressure systems so that our gas control center will see an alarm should the monitoring device indicate a high or low pressure alarm. In the event a system is shut down by the slam-shut devices described above, the remote monitors will enable us to respond more quickly to restore service to customers. NiSource will develop project-specific risk reviews and plans detailing accountability and responsibility for activities during the construction process. This will include individual responsibility for system operation, configuration and monitoring during the construction and “tie-in/gas up” process. The plans will identify the specific tasks (operating valves, monitoring pressure, notifying first responders) required to mitigate risk during critical steps. The plans will also identify follow up actions to be taken in an abnormal condition including identifying critical locations to place assets for immediate shut down if needed.

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.