It’s unknown when Plymouth residents will be able to return to their homes after an explosion and fire at a nearby natural gas facility Monday morning triggered fears of a second, larger explosion.
Up to 1,000 residents and agricultural workers were evacuated from a two-mile radius around Northwest Pipeline in south Benton County after the explosion, which caused slow leaks from a massive storage tank and injured five people.
Hazardous materials experts entered the liquefied natural gas facility Monday afternoon for the first time nearly eight hours after the initial explosion and fire inside a building at Northwest Pipeline, a subsidiary of Williams Partners.
The 8:22 a.m. explosion sent shrapnel into a 14.6-million-gallon storage tank, rupturing it and starting the gradual leak of super-cold liquefied natural gas. William Partners officials say the tank was only one-third full.
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A Washington State Patrol robot and a Williams Partners helicopter were sent in Monday afternoon. Joe Lusignan, Benton County Sheriff's Office spokesman, said the hazardous material experts assessed damage after reviewing information gathered by the robot and helicopter.
The evacuation remained in place Monday night and Highway 14 between Interstate 82 and Paterson was closed, he said. Officials encouraged citizens to stay out of the area.
Traffic also was shut down on the Columbia River and the rail lines near the plant.
The river traffic and Highway 14 were expected to reopen late Monday. The evacuation zone was reduced to a one-mile radius.
“This is considered a large leak,” Lusignan said.
The experts and Williams Partners employees planned to enter the plant a second time Monday night to see if there was a way to stop the tank from leaking, said Capt. Devin Helland of Benton Fire District 1.
The vaporized natural gas could explode if mixed with the right amount of oxygen and atmosphere and there was an ignition source, said Capt. Jeff Ripley, also with the fire district. Such a blast would kill anyone within a radius of up to three-quarters of a mile.
First responders had to wait for the natural gas to dissipate before entering the facility to investigate. That happened slowly, because the gas is cooled to minus 260 degrees. It froze as it leaked, plugging the hole, until the ambient temperature warmed the ice plug, allowing the liquid to continue to leak and vaporize, Ripley explained. The cycle of freeze, thaw and vaporize repeated itself over and over again.
An east wind helped disperse the natural gas, which was not considered dangerous, officials said. A large cloud of fumes floated in the area as the gas escaped into the air.
Northwest Pipeline shut down the pipeline and the facility at Christy Road and evacuated the 14 company workers who were on site at the time.
One worker was taken to a burn center and four others to local medical facilities, Ripley said. Up to 120 responders were in Plymouth Monday afternoon, including regional fire crews and law enforcement agencies, state Department of Transportation officials and Washington state troopers.
Williams Partners spokeswoman Michele Swaner said they still do not know the cause of the explosion.
“We will have to go in and go through piece by piece, look at the facility and where the whole incident began,” she told the Herald. “It just takes a little bit of time.”
Investigators from the state Utilities and Transportation Commission also will investigate.
Benton County deputies went door to door Monday morning to get people out of homes and businesses. AgriNorthwest and Crop Production Services have facilities in the Plymouth Industrial Park near Northwest Pipeline and there are also vineyards and orchards in the area.
The fumes were causing the deputies to feel nauseous, Lusignan said.
Kyla Christianson and her children, who were home for spring break, watched the scene from their house about a quarter mile from the plant.
“There were these two (tanks) that the gas sits in and the fire was in between them,” she said. “The ambulances were hauling down there. You could smell gas. It was in the air and making people sick.”
Some of the evacuees went across the river to the fairgrounds in Hermiston, where the Red Cross responded to help displaced residents.
The pipeline at the Plymouth liquefied natural gas facility connects to a natural gas pipeline which runs through Kennewick and Pasco in populated areas. Williams Pipeline is the transporter, with the line running from the top of Washington state at the Canadian border down to almost the New Mexico border.
The 20-inch-wide main line is operating, but the segment that’s extended to the plant has been closed off, Swaner said. She didn’t know how long the plant would be shut down.
The Northwest Pipeline facility has two storage tanks, each about 90 feet tall, and four vaporizers on about 72 acres, according a recent inspection by the Utilities and Transportation Commission. The facility began operating in 1975 and was expanded in 1979.
The commission last inspected the facility in November 2013, said Amanda Maxwell, the commission’s communications manager.
“It was a clean inspection,” said David Lykken, the commission’s director of pipeline safety. Inspectors found no violations of pipeline safety regulations.
Inspections, which occur annually, include a review of operation and maintenance records and a check of the plant itself to make sure it is maintained according to safety regulations, he said.
Swaner said Williams Partners goes above and beyond what is required and spends a lot of time and money on making sure that the company’s pipelines are well-maintained and inspected on a regular basis.
“Pipelines are highly regulated and safety is of utmost concern,” Swaner told the Herald. “We work with emergency responders and have mock emergencies so that we know what the duties are and the hours are, so we work as a coordinated team.”
Tank ruptures are rare, Lykken said. Local fire and law enforcement officials could not recall a similar incident in the Tri-Cities in recent decades.
This time the incident didn’t involve an underground pipeline, but there have been at least three major gas explosions in the Pacific Northwest in the past 15 years.
In 2003, a 26-inch-wide Williams-Northwest line in Auburn ruptured, shooting debris and rocks hundreds of feet into the air. There was no fireball and no one was injured, but hundreds of people were evacuated. Swaner said that Auburn line was completely replaced in 2006.
In 1999, an Olympic Pipe Line Co. line carrying liquid gas ruptured near Bellingham, causing a huge explosion and killing three people.
That same year, a Williams-Northwest natural gas pipeline exploded near Pendleton in rural Umatilla County. No one was killed but it left some 10,000 customers without heat for days.
-- Herald reporters Tyler Richardson and Kristen M. Kraemer contributed to this story.