Regulators release report into 2014 explosion at liquid natural - NBC Right Now/KNDO/KNDU Tri-Cities, Yakima, WA |

Regulators release report into 2014 explosion at liquid natural gas facility

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Repairs are almost complete to one of the tanks damaged during the explosion. Repairs are almost complete to one of the tanks damaged during the explosion.

OLYMPIA, WA – Federal and state pipeline safety regulators Wednesday released their investigation into the March 2014 explosion at the Williams Northwest Pipeline facility in Plymouth.

The U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration and the Utilities and Transportation Commission worked together on the two-year long investigation into the cause of the explosion that injured six employees.

Fire and Explosion at Natural Gas Plant near Plymouth

The investigation found the leading cause of the explosion was inadequate procedures that allowed oxygen to remain in the system. The mix of the oxygen and gas ignited during start up causing the failure and explosion.

The investigation also identified additional factors that led to the conditions generating the explosion, including:

  • Procedures that lacked sufficient details for employees to follow and obtain consistent results;
  • Procedures that did not adequately address the piping configuration and allowed oxygen to remain trapped in portions of the system;
  • Lighting of a process heater before the system was at full operating pressure; and
  • Drastic pressurization of the system immediately prior to startup, which created excess heat.

Lab tests conducted as part of the investigation concluded that under a higher pressure and lower temperature, the oxygen and gas mixture ignited spontaneously. This confirmed that the explosion was possible under the conditions at the facility on the day of the incident.

As a result of this investigation, the UTC submitted a violation report to PHMSA that alleges the company violated federal pipeline regulations, and recommend the agency impose a penalty. The UTC also outlined a number of opportunities to strengthen pipeline safety through stronger regulation and technical assistance. The commission asked PHMSA 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.

The Plymouth-Liquefied Natural Gas Peak Shaving Plant is located on the Columbia River near the central Washington town of Plymouth. The plant liquefies natural gas during times of low demand and stores it until the demand increases. When gas is needed, the plant vaporizes the liquefied gas and introduces it into the transmission system.