A large explosion rocked a natural gas processing plant on the Washington-Oregon border Monday, injuring four workers, causing about 400 people to evacuate from nearby farms and homes, and emitting a mushroom cloud of black smoke that was visible for more than a mile.
The 8:20 a.m. blast at the Williams Northwest Pipeline facility near the Washington town of Plymouth, along the Columbia River, sparked a fire and punctured one of the facility's two giant storage tanks for liquefied natural gas.
Benton County Sheriff Steven Keane said a relatively small amount of gas leaked from the tank to the ground in a moat-like containment area. But it then evaporated, blowing away to the northeast, he said.
"I think if one of those huge tanks had exploded, it might have been a different story," Keane said.
The fire at the facility about 4 miles west of Plymouth was extinguished within a couple of hours.
One of the four injured workers was transported to a Portland, Ore., hospital specializing in burns, he said. The other three were taken to Good Shepherd Medical Center in Hermiston, Ore., where spokesman Mark Ettesvold said they were treated in the emergency room for injuries that did not appear to be life-threatening.
More than a mile away across the Columbia River, the explosion shook Cindi Stefani's home.
"It was just a very loud boom," she said. "I looked across the river and saw a giant mushroom cloud and flames at least a couple hundred feet high."
Animals on neighboring farms were running around, she added.
"At that point we were pretty scared. I was thinking, 'We need to get out of here.'"
Deputies went door to door to homes and farms within a 2-mile radius, evacuating about 400 residents as a precaution.
Buses were provided for those without cars, and a shelter was set up across the river in Oregon at the Umatilla County Fairgrounds. As part of the evacuation, Highway 14 and railroad tracks were shut down.
Deputy Joe Lusignan said the voluntary evacuation could last overnight. No one was being prevented from returning to the evacuation area, which was calculated based on the damage expected if one of the two storage tanks blew up.
The facility provides supplemental gas during times of high demand for a 4,000-mile pipeline stretching from the Canadian border to southern Utah. Its two storage tanks for liquefied natural gas each have a capacity of 1.2 billion cubic feet, Williams spokeswoman Michele Swaner said. The one that punctured was about a third of the way full.
Swaner said the 14 employees working at the time were all evacuated and accounted for. A total of 17 or 18 people work at the facility.
She added it was too early to determine the extent of the damage or the cause of the explosion. The pipeline was shut down in the area of the storage facility, but was still carrying gas on other stretches.
Video taken by a Washington State Patrol bomb squad robot was being evaluated, and plans were being developed to send up a helicopter for an aerial assessment of the facility, authorities said.
A pipeline engineer with the Washington Utilities and Transportation Commission will investigate the cause of the explosion and communicate with the western region of the U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration, the commission said.
Workplace safety investigators from the Washington Department of Labor & Industries will join the investigation, department officials said.
The state Pipeline Safety Program regulates 28 pipeline companies and inspects more than 24,000 miles of natural gas and hazardous-liquid pipelines in Washington.
Williams operates about 15,000 miles of interstate natural gas pipelines, according to its website.
The liquefied natural gas facility is owned by Williams Partners' subsidiary Northwest Pipeline LLC.
There was no pipeline rupture, and no customers were affected, company officials said.
A secretary with the Patterson School District, about 7 miles away, said it provided three school buses to help with the evacuation. Students are on spring break, Rachelle Munn said.
Barnard reported from Grants Pass, Ore.
Associated Press writers Doug Esser and Donna Gordon Blankinship in Seattle contributed to this report.