(Jim Urquhart ~ Associated Press)
Conditions on the swollen river have prevented a thorough assessment and hampered efforts to find the cause of Friday's break in the 12-inch pipeline that spilled an estimated 1,000 barrels of crude oil. The river was flowing too high and swiftly to launch a boat, and forecasters said mountain snowmelt was adding to the swollen river.
Much of the riverbank also is covered with dense underbrush, making it difficult to walk long portions of shoreline. Most observations have been made through aerial flights. Officials have speculated that the high water may push pools of oil into areas that haven't yet been damaged.
Exxon Mobil Corp. and federal officials said they have only seen oil about 25 miles downstream from the site of the break near Laurel, but Gov. Brian Schweitzer said he believes it has traveled hundreds of miles to North Dakota.
"At seven miles per hour, some oil is already in North Dakota. That's a given," Schweitzer said. "I'm asking everyone to get out there and report what you see on the river."
Exxon officials did not immediately address Schweitzer's claims.
Company officials have acknowledged under political pressure that the scope of the leak could extend far beyond the 10-mile stretch that they initially said was the most affected area. Sherman Glass, Exxon's president of refining and supply, said crews have identified 10 places where oil has pooled in the heaviest amounts within 20 miles of the break.
The surge of water raises concerns it will carry oil into areas that have not yet been affected, said Tom Livers, deputy director of the state Department of Environmental Quality. It also would make it difficult for the 250 cleanup workers to get to known damaged areas.
Exxon Mobil Pipeline Co. president Gary Pruessing has said the company is not limiting the scope of the cleanup to the immediate site. The company planned to test the river's conditions with a jet boat, with eight more on standby if the launch is successful, Glass said.
The pipeline burst Friday upstream from a refinery in Billings, where it delivered 40,000 barrels of oil a day. The 20-year-old Silvertip pipeline followed a route that passes beneath the river.
The cause of the rupture has not yet been determined, but company and government officials have speculated that high waters in recent weeks may have scoured the river bottom and exposed the pipeline to damaging debris.
Pruessing said Tuesday for the first time that it took a half-hour to shut down and seal off the pipeline after workers spotted a dip in pressure. The line was temporarily shut down in May after Laurel officials raised concerns that it could be at risk as the Yellowstone started to rise.
The company decided to restart the line after examining its safety record and deciding it was safe, Pruessing said.
The U.S. Department of Transportation, which oversees pipelines, notified Exxon Mobil in July 2010 of seven potential safety violations and other problems along the pipeline. Two of the warnings faulted the company for its emergency response and pipeline corrosion training, and another noted a section of pipeline over a ditch covered with potentially damaging material and debris.
Transportation Department spokeswoman Patricia Klinger said the company has since responded to the warnings and the case was closed. Company spokesman Alan Jeffers said there was no direct connection between those problems and the pipeline failure.
The impact on wildfire has not been assessed, although Exxon said one case -- a dead duck -- had been reported but not confirmed. The Billings Gazette has run pictures of a turtle and a group of pelicans apparently with oil on them.
The rupture site is upstream of Yellowstone National Park, which is about 110 miles away. Officials said the river portion in the park is not threatened by the spill.
But the stretch of the Yellowstone where the spill occurred contains sauger, bass catfish, goldeye, trout and, farther downstream, below Miles City, native pallid sturgeon. If another surge of water pushes oil into back channels as expected, it could threaten fisheries, said Bruce Farling, executive director of Trout Unlimited's Montana chapter.
Farling said there are many fish eggs and recently hatched fish in those channels.
"If we get a bunch of oil in some of these backwater areas, these are precisely where these small fish rear," Farling said.