Three weeks after a broken Exxon Mobil pipeline spilled 1,000 barrels of oil into the Yellowstone River, federal officials remain unsure how many pipelines carrying hazardous fuels cross the nation's rivers and streams, nor can they say how deeply those pipelines are buried.
The spill into the Montana river amid historic flooding this month drew attention to what had long been an overlooked part of the nation's energy infrastructure: the presence of pipelines underneath rivers coursing throughout the country. The spill raised concern that other underwater pipelines may have been exposed to debris by high and fast-moving waters that swept much of the U.S. in recent months.
As regulators scramble to gauge what other lines might be at risk, lawmakers from both parties are raising alarms that another spill could be imminent unless the government steps up oversight of the largely self-regulated pipeline industry.
"If we don't know where the (pipelines) are in the ground and how many crossings are under rivers and streams so we can check on them, we're asking for another catastrophe," said U.S. Sen. Jon Tester.
Tester, a Montana Democrat, said he was dismayed that the U.S. Pipeline and Hazardous Material Safety Administration could not immediately provide an inventory of pipeline crossings when he requested the information. "We had massive water this year, make no mistake about that. We need to re-evaluate the impact of those floods on the river crossings," he said.
Pipeline safety officials on Wednesday gave The Associated Press a preliminary estimate of 35,000 river, stream and lake crossings within the country's half-million-mile network of natural gas and hazardous liquid transmission pipelines. They said a review of pipeline crossings in the Missouri River basin in Montana and Wyoming is under way and there are plans to expand that effort nationwide.
But the federal government still can't pinpoint exactly where the crossings are, and has no information about additional spots where smaller gas distribution and gathering pipelines traverse streams, said spokesman Damon Hill.
Federal regulations require that pipelines crossing rivers be buried at least four feet underneath most riverbeds. They can be placed at shallower depths if the soil is rocky. There is no requirement for companies to periodically re-evaluate the original depth.
Flooding rivers can scour riverbottoms and expose pipelines to powerful water currents and damaging debris. That's the prevailing theory of what happened to Exxon Mobil in Montana although the investigation into the spill is not complete.
Exxon Mobil had recently examined the Montana pipeline prior to its July 1 failure in response to local officials' concerns that the river bank was eroding amid violent river flows brought on by a record winter snowpack. Yet when another company with an adjacent natural gas line shut down the line over floodwater concerns, Exxon Mobil did not, a decision the company has since acknowledged was a mistake.
A survey conducted by Exxon Mobil last December indicated its pipeline was buried at least five feet beneath the river bottom.
Michigan Republican Rep. Fred Upton, who chairs the Committee on Energy and Commerce, said he was concerned current depth requirements did not go far enough, particularly in light of recent accidents. Last year, an Enbridge Inc. pipeline ruptured in Upton's district, spilling more than 800,000 gallons of oil into the Kalamazoo River.
"The Yellowstone River incident is disconcerting in that it appears the operator and regulators had properly maintained and inspected the line where it ruptured, yet the spill still occurred," Upton said. "My concern is not that regulators are not doing their job, but rather whether or not the proper regulatory requirements are in place to prevent future incidents."
Exxon Mobil Pipeline Co. and numerous other witnesses are scheduled to testify at a hearing before the committee on Thursday.
The pipeline safety agency says operators must protect their lines from damage, no matter the depth.
But pipelines that were built and laid in the ground before 1970 _ when major pipeline safety rules went into effect _ were allowed to remain at their original depth, even if it was less than four feet. Even now, if pipeline operators repairing their pipes find that some segments are too short to meet the depth requirements, the rules let companies keep those segments buried where they are.
One proposed pipeline that would carry crude oil extracted from western Canada's tar sands to refineries in the U.S would cross water bodies 1,904 separate times, including 389 crossings in Montana, 354 in South Dakota, 160 in Nebraska, 368 in Oklahoma and 633 in Texas.
The Keystone XL project _ which would run from Alberta, Canada to the Texas Gulf Coast _ has drawn fierce opposition from environmental groups who call it an ecological disaster waiting to happen.
"This pipeline would go through the most productive parts of the Ogallala aquifer, the Sandhills region, where there aren't any other oil pipelines," said Anthony Swift, a policy analyst with the Natural Resources Defense Council which wants the government to give the project more rigorous environmental review. "The water table is at ground level in some of that region, so a spill could cause an instant problem."
Pipeline company TransCanada carefully selected each crossing for the Keystone XL project after weighing possible threats of erosion or the potential for floods to scour the riverbed, said spokesman Terry Cunha.
The company plans to place the pipe 25 feet or more below the riverbed at major river crossings, Cunha said.
The furor over the Yellowstone River spill comes 15 years after an even more damaging flood event in Texas in which eight ruptured pipelines spilled more than 35,000 barrels of oil and oil products into the San Jacinto River. More than 500 people were injured when the oil ignited.
That event spurred the National Transportation Safety Board to push for companies to adopt guidelines on how to deal pipeline crossings on flooded rivers. Those guidelines were adopted in 2005.
Former Conoco Pipe Line Co. president Tom Miesner said the guidelines reinforced the industry's longstanding focus on safety.
"No one wants a leak at all, and some of the most expensive leaks are going to be ones that occur in rivers," said Miesner, now an industry consultant and author.
Burke reported from San Francisco.