On February 23, 2018, about 6:38 a.m. local time, a natural gas-fueled explosion occurred at 3534 Espanola Drive, Dallas, Texas, injuring all five occupants, one fatally. The one-story two-bedroom residence sustained major structural damage. Following the explosion, National Transportation Safety Board investigators located a through-wall crack in the 71-year-old natural gas main that served the residence and positive gas measurements leading from this crack to the residence.
In the 2 days before this explosion, two gas-related incidents occurred on the same block at houses that were served by the same natural gas main, each resulting in significant structural damage and burn injuries to one occupant. The first occurred on February 21, 2018, at 5:49 a.m., and resulted in one injury involving second-degree burns and significant structural damage to 3527 Durango Drive. The second incident occurred on February 22, 2018, at 10:21 a.m., and resulted in one injury involving second-degree burns and significant structural damage to 3515 Durango Drive.
The probable cause of the explosion at 3534 Espanola Drive was the ignition of an accumulation of natural gas that leaked from the gas main that was damaged during a sewer replacement project 23 years earlier and was undetected by Atmos Energy Corporation’s investigation of two related natural gas incidents on the 2 days prior to the explosion. Contributing to the explosion was Atmos Energy Corporation’s insufficient wet weather leak investigation procedures. Contributing to the severity of the explosion was Atmos Energy Corporation’s inaction to isolate the affected main and evacuate the houses. Contributing to the degradation of the pipeline system was Atmos Energy Corporation’s inadequate integrity management program.
As a result of this investigation, we made the following new safety recommendations.
To the Pipeline and Hazardous Materials Safety Administration:
- Expand incident reporting requirements in Title 49 Code of Federal Regulations Part 191 so that events that may meet the definition of “incident” are immediately reported to the National Response Center even when the source of the natural gas has not been determined. (P-21-1)
- Evaluate industry’s implementation of the gas distribution pipeline integrity management requirements and develop updated guidance for improving their effectiveness. The evaluation should specifically consider factors that may increase the likelihood of failure such as age, increase the overall risk and limit the effectiveness of leak management programs. (P-21-2)
- Assist the Railroad Commission of Texas in conducting the audit recommended in Safety Recommendation P-21-4. (P-21-3)
To the Railroad Commission of Texas: With assistance from the Pipeline and Hazardous Materials Safety Administration, conduct a comprehensive audit of Atmos Energy Corporation’s incident-reporting practices; policies and procedures for responding to leaks, fires, explosions, and emergency calls; and integrity management programs. (P-21-4)
To the Dallas Fire-Rescue Department:
- Revise the continuing education requirements for your arson investigators to include training on building fuel gas systems. (P-21-5)
- Revise your procedures to require gas monitoring after the occurrence of a gasrelated structure fire or explosion. (P-21-6)
- Develop and implement a formal process to alert appropriate local, state, and federal agencies of potential systemic safety issues that should be investigated further. (P-21-7)
To Atmos Energy Corporation:
- Provide initial and recurrent training to Dallas Fire-Rescue Department arson investigators and firefighters on the local natural gas distribution system and associated hazards. (P-21-8)
- Develop and implement more rigorous inside leak investigation requirements in response to fires and explosions when gas involvement cannot be excluded, including clear guidance on pressure testing and inside gas measurements and the potential need to return to the property after firefighters have departed. (P-21-9)
- Develop a clear procedure to coordinate with local emergency responders when investigating all fires and explosions that may be gas related to conclusively determine whether your system can be excluded as a potential contributor, and collecting the necessary evidence to support the conclusion of your investigations. (P-21-10)
- Revise your policies and procedures for responding to leaks, fires, explosions, and emergency calls to address the challenges caused by wet weather conditions. The revised policies and procedures should include: (1) leak investigation methods that are reliable in wet weather; (2) leak investigation procedures that assess all viable gas migration paths; (3) criteria for when to shut down or isolate gas distribution systems and pressure test main and service lines; and (4) an alternate safe response such as evacuation when reliable leak investigations are not possible due to wet weather or other circumstances. (P-21-11)
- Without delay, assess your integrity management program, paying particular attention to the areas identified in this investigation, and revise the program to appropriately consider: (1) threats that degrade a system over time, and (2) the increased risk that can result from factors that simultaneously increase the likelihood and consequence of failure. (P-21-12)
To the Gas Piping Technology Committee:
- Develop additional guidance that identifies steps gas distribution operators can take to safely respond to leaks, fires, explosions, and emergency calls, considering the limitations due to wet weather conditions, that includes: (1) criteria for when to shut down or isolate gas distribution systems, pressure test main and service lines, and begin evacuations; (2) leak investigation methods that are reliable in wet weather, (3) require an alternate safe response, such as an evacuation when reliable leak investigations are not possible due to wet weather, and (4) leak investigations that assess all viable gas migration paths, including granular backfill and crawlspaces. (P-21-13)
- Develop guidance that identifies steps that gas distribution operators can take to ensure that their gas distribution integrity management program, at a minimum, appropriately considers: (1) threats that degrade a system over time, and (2) the increased risk that can result from factors that simultaneously increase the likelihood and consequence of failure. (P-21-14)
We reiterated the following safety recommendations.
To the International Code Council: In coordination with the Gas Technology Institute and the National Fire Protection Association, incorporate provisions in the International Fuel Gas Code
that requires methane detection systems for all types of residential occupancies with gas service. At a minimum, the provisions should cover the installation, maintenance, placement of the detectors, and testing requirements. (
P-19-006)
To the National Fire Protection Association: In coordination with the Gas Technology Institute and the International Code Council, revise the National Fuel Gas Code, National Fire Protection Association 54 to require methane detection systems for all types of residential occupancies
with gas service. At a minimum, the provisions should cover the installation, maintenance, placement of the detectors, and testing requirements. (
P-19-007)
To the Gas Technology Institute: In coordination with the National Fire Protection Association and the International Code Council, work to develop standards for methane detection systems for all types of residential occupancies in both the International Fuel Gas Code and the National Fuel Gas Code, National Fire Protection Association 54. At a minimum, the provisions should cover the installation, maintenance, placement of the detectors, and testing requirements. (
P-19-008)
