Cause of Yellowstone oil spill remains unknown

WASHINGTON — It will likely be months before investigators know what caused an ExxonMobil oil pipeline to rupture near Billings, Mont., spilling about 1,000 barrels of crude oil into the Yellowstone River, a federal safety official said Thursday.

Thus far, investigators are unaware of any safety violations by ExxonMobil related to the spill, Cynthia Quarterman, administrator of the Pipeline and Hazardous Materials Safety Administration, told a congressional hearing. The spill has fouled shoreline and contaminated backwaters along dozens of miles of the scenic river.

The oil giant is working on a plan to lay a new section of pipe 30 feet below the river to replace the damaged pipe responsible for the spill, ExxonMobil Pipeline Co. President Gary Pruessing said. The flow of oil through the company's Silvertip pipeline has been shut off since the July 1 accident.

ExxonMobil hasn't yet submitted its plan for the replacement pipe to the safety administration, which must approve the project before it can go forward, Quarterman told the House Transportation and Infrastructure Committee's pipeline subcommittee.

The agency hasn't yet determined how deep the replacement pipe will have to be buried except that it will be deeper than the pipe that ruptured, she said. The depth will depend on the plan ExxonMobil submits, but horizontal drilling will be required, she said.

Federal regulations require that pipelines that cross underneath riverbeds be buried at least four feet, Quarterman said. The result of tests conducted by ExxonMobil prior to the accident indicated the pipeline beneath the river bottom was buried about five feet, she said.

At the time of the accident, unusually high amounts of mountain snowmelt had increased water level and velocity in the river to historic levels. That, in turn, increased the possibility for erosion of the riverbed covering the oil pipeline.

Safety officials were concerned enough about that section — as well as other pipelines in parts of the country that suffered flooding — that they were checking daily withExxonMobil , Quarterman said.

It will likely be August or September before water levels in the river are low enough to exhume the section of damaged pipe responsible for the spill, she said. It will be about two months after that before investigators identify a cause, she said.

The pipe replacement will also require moving two shutoff valves, Pruessing said.

He also said he's confident no more than 1,000 barrels of oil leaked into the river. Quarterman said her agency won't know for certain how large the leak was until it examines records at the company's control room in Houston.

A barrel of oil equals 42 gallons.

Republican members of the committee praised the oil and gas industry's safety record, noting that the number of inland pipeline breaks and spills have been declining in recent years despite several high-profile accidents. A Pacific Gas & Electric natural gas pipeline explosion last year in San Bruno, Calif., killed eight people and injured dozens of others. An Enbridge Inc. pipeline ruptured last July in southwest Michigan, spilling more than 800,000 gallons of oil into the Kalamazoo River.

The incidents are "cause for concern, but not for alarm," said Rep. Bill Shuster, R-Pa., the subcommittee's chairman.

But Sen. Jon Tester, D-Mont., told the committee he's frustrated because ExxonMobil officials have changed their initial statements on several key elements of the accident, including how long it took to shut the pipeline down, how far downstream the oil has traveled and how deep the pipeline was buried.

"And in this situation, Exxon was tasked with regulating itself. Regulators were not on the job. And now we're paying a price for it," Tester said.

The spill has already begun to figure in next year's Senate race in Montana. Tester emphasized at the hearing, which was webcast, that he has demanded ExxonMobil promise not to lay off workers at its refinery near Billings while the pipeline is shut down. Rep. Dennis Rehberg, R-Mont., Tester's likely opponent for the seat, took credit for initiating a phone call between federal public health agencies to discuss the possible health impacts of the spill.

Relations between ExxonMobil officials and Montana Gov. Brian Schweitzer, a Democrat, have become openly hostile. Last week, Schweitzer pulled out of the incident command group responding to the leak. His office said ExxonMobil was barring reporters from meetings held at a local hotel in violation of the state's open meetings law and preventing public access to information about the pipeline and the leak.

The hostilities continued Thursday as Schweitzer released a letter to Pruessing chastising the oil executive for telling a news reporter that he'd tried unsuccessfully several times to reach the governor.

"It is not that hard to reach me. The governor's office has been in the State Capitol building since 1902," Schweitizer wrote. He supplied his phone number.