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State says inadequate procedures caused Plymouth gas explosion

Leaking natural gas vapors in 2014

Liquefied natural gas leaks from a damaged storage tank at the Williams Northwest Pipeline facility near Plymouth in March 2014.
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Liquefied natural gas leaks from a damaged storage tank at the Williams Northwest Pipeline facility near Plymouth in March 2014.

Federal and state regulators say improper procedures caused a 2014 natural gas explosion at a facility in Plymouth along the Columbia River and have recommended the company be penalized.

An investigation into the explosion at the liquid natural gas plant of Williams Partners found inadequate employee procedures allowed oxygen to remain in the facility’s system, a release said. That oxygen caused gas to ignite when the facility restarted.

Five people were hurt in the explosion that sent shrapnel into a 14.6-million-gallon tank and other buildings and triggered fires. The state’s report says the damage totaled about $45.7 million — much of it contained to the plant’s grounds but also affecting some nearby railroad tracks.

Williams Partners had no response to the findings late Wednesday afternoon.

Regulators did not specify how Williams should be penalized. The state’s report said the company has addressed the problems that contributed to the explosion by either correcting design flaws in the rebuilt facility, which was scheduled to restart full operations this spring, or by writing and implementing new procedures.

“The (state Utilities and Transportation Commission) also outlined a number of opportunities to strengthen pipeline safety through stronger regulation and technical assistance,” a state release said, adding that regulators were asked to “consider administrative actions or proceedings to incorporate the lessons learned from the investigation to ensure that LNG liquefaction facilities, such as Plymouth, continue to operate safely.”

Five workers were injured, one of them suffering serious burns. About 1,000 Plymouth residents and agricultural workers working within a few miles of the rural facility were evacuated. Some reported feeling sick after inhaling the vapor cloud.

All those injured in the explosion on March 31, 2014, worked at the plant. Four workers were treated and later released, while one worker was hospitalized for burns.

About 1,000 Plymouth residents and agricultural workers working within a few miles of the facility were evacuated. Some reported feeling sick after inhaling the vapor cloud that resulted from the explosion. A nearby rail line was damaged and dozens of trains were delayed until repairs were completed.

Before the explosion, the facility was last inspected in November 2013 by the state Utilities and Transportation Commission and no issues were found.

A spokesperson with Williams Partners said at the time that the company went above and beyond what is required for safety and maintenance, and spends a lot of time and money on making sure that its pipelines are well maintained and inspected regularly.

The federal Pipeline and Hazardous Materials Safety Administration and the state’s Utilities and Transportation worked for two years on its investigation.

The agencies traced the origin of the problems that caused the explosion back to November 2013, when three valves in the plant’s system were removed, allowing air to enter the system.

The system was purged when new valves were installed in mid-March 2014, but “because the blowdowns were only done to approximately 5 (pounds per square inch) instead of the industry recognized zero to 1 (pounds per square inch), oxygen remained in the system,” according to a report filed by Williams with regulators.

14.6 million gallon storage tank ruptures

$45.7 million estimated damage

Following that guideline was particularly important given the piping configuration at the facility, regulators noted.

That remaining oxygen caused gas to ignite, leading to a rolling detonation that flowed backward through the system when workers went to restart operations on March 31.

Williams officials worked closely with regulators during the investigation. Among the changes the company made to the plant following the explosion were a simplification of the facility’s purification system, installation of new components and moving the plant’s control room away from critical areas. Procedures concerning purging or restarting the system were modified.

A report released by Seattle-based think tank Sightline in February 2016 criticized Williams for downplaying the explosion, and said the company and others handling liquid natural gas benefit from lax regulations and oversight.

No Williams Partners officials were interviewed for Sightline’s report and company spokesman Tom Droege said at the time “unfortunately it contains numerous inaccuracies.”

“We have cooperated in a full and transparent manner with the various agencies throughout the investigative process. We have also worked with the energy industry to share lessons learned and advise others of our findings,” he said.

He also noted the company met with members of the Plymouth community to answer questions and address concerns related to the incident.

“Throughout the process, our No. 1 priority has been the safety of our employees and the community,” Droege said.

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