The main cause of an explosion in 2014 at a southeastern Washington natural gas facility was inadequate procedures that allowed oxygen to remain in the system.
A pressure vessel ruptured at the Williams Northwest Pipeline facility in Plymouth, Washington, March 31, 2014, injuring six employees and causing tens of millions of dollars in damage, Pipeline and Hazardous Materials Safety Administration (PHMSA) officials said. It turns out the mix of oxygen and gas ignited.
Other factors investigators cited were procedures that lacked details for employees to follow and procedures that didn’t address the piping configuration and allowed oxygen to end up trapped.
Two storage tanks hold up to 14 million gallons of liquid natural gas to meet peak winter demands on the pipeline that carries gas through Washington, Oregon, Idaho, Wyoming, Utah and Colorado.
In addition to the six injured workers, the blast forced an evacuation of 400 residents and agricultural workers within a two-mile radius of the facility. River, highway and train traffic ended up restored the day after the blast, though authorities maintained a one-mile exclusion zone around the facility because of the ongoing risk of an explosion.
Shrapnel from the blast punctured one of the two on-site storage tanks containing super-cooled gas in liquid form.