Washington (Platts)--6Jul2011/340 pm EDT/1940 GMT

Montana Governor Brian Schweitzer said Wednesday that boulders scouring the bottom of the flooded Yellowstone River likely ripped into ExxonMobil's Silvertip Pipeline, sending as much as 1,000 barrels of crude hundreds of miles downstream.

"If that pipeline's 5-feet-deep down there, it wouldn't surprise me a bit if something hooked onto that thing," he said.

In a telephone interview with Platts, Schweitzer said he has not gotten a consistent answer from the company about how deep it buried the pipeline under the river. But he suspects its proximity to the water and the recent flooding caused the pipeline to fail.

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"Last year they said it was 12 feet deep in the sediment," he said. "Now they're saying it was maybe 5- to 6-feet-deep. Who knows? I can tell you what the Yellowstone River looks like right now. That is a raging torrent, trees the size of your house, they are floating down that river.

"Underneath, you've got boulders working their way down from the Rocky Mountains, and their full intent is to get to North Dakota," he continued. "By the time they get to North Dakota, they'll be the size of a baseball, but right now they're the size of your car and they're scouring and gouging the bottom of that river."

The Silvertip Pipeline burst late Friday at a river crossing near Laurel, Montana, leaking an estimated 750-1,000 barrels of crude into the Yellowstone River. ExxonMobil said it does not yet have a restart plan in place.

Schweitzer said the state would inspect 88 other pipelines that cross major streams and rivers. He said inspectors are asking companies about the pipeline designs, flow rates, products being shipped, what valves they use and documentation of their latest inspections for corrosion.

The governor declined to list the pipeline operators, but said he had received no pushback from the companies.

"It's just due diligence," Schweitzer said. "We'd hate to have another one like this occur, so we want to make sure we are once again reviewing the integrity of those pipelines." GOVERNOR SAYS SILVERTIP LEAK SHOULD NOT IMPEDE KEYSTONE XL PLANS

Schweitzer said ExxonMobil's oil spill should not impede the construction of another pipeline that crosses the Yellowstone River -- TransCanada's Keystone XL pipeline.

The US State Department is deciding whether to approve the high-profile application to build a system transporting crude from Canada's oil sands to the Texas Gulf Coast.

A supporter of Keystone XL, Schweitzer said he took comfort in two key ways TransCanada's design would differ from ExxonMobil's Silvertip. He said it would sit at least 25 feet below the riverbed and have automatic shutoff valves.

"Keystone is a completely differently designed system," he said. "They don't lay that pipeline in the bed of the river the way the Silvertip was. They actually use horizontal boring and that's actually the kind of technology that all new pipelines are using today...So there is no physical contact with the water."

A State Department spokeswoman said the agency would take ExxonMobil's pipeline rupture under consideration during its Keystone XL review.

Schweitzer said he hopes the recent spill in his state has no bearing on TransCanada's project.

"I don't think one ought to confuse what happens with this particular old technology, Silvertip, with what will occur in the future," he said. "Unless people are willing to park their cars and move into a cave and live naked and eat nuts, we're going to continue to produce energy and that energy needs to be moved to the source of consumption."

As for the cleanup happening along the Yellowstone River, Schweitzer said he gives ExxonMobil an "incomplete" grade, but is pleased with the federal response, led by the Environmental Protection Agency.

"They understand that Montana is the client," he said. "When the state of Montana says it's done, it's done. Not when some bureaucrat in Washington, DC, or some corporate executive in Houston, Texas, says it's done."

--Meghan Gordon, meghan_gordon@platts.com