MAN:So that is a pipeline that has busted and has flooded the neighborhood.

　　JUDY WOODRUFF:A local resident described the scene in the small town of Mayflower on Friday after Exxon's Pegasus pipeline ruptured close to his home.

　　MAN:I mean, look. Incredible. And that is oil.

　　23.jpgJUDY WOODRUFF:And not just any oil, a type of heavy crude called diluted bitumen, from the tar sands of Western Canada and similar to what the proposed Keystone XL Pipeline would carry.

　　Running from Patoka, Ill., to Nederland, Texas, the Pegasus pipeline is capable of transporting 96,000 barrels of oil a day. It passes through this Little Rock suburb, and also through 13 miles of the close-by Lake Maumelle watershed, leaving many concerned with the risks posed to Arkansas' water supply.

　　Yesterday at a bird shelter in nearby Russellville, specialists cleaned ducks covered in the heavy crude. Investigators are still trying to find out what caused the rupture. According to Exxon's estimates, between 3,500 and 5,000 barrels of oil spilled. More than 20 homes were evacuated.

　　Last year in the U.S., 364 pipeline spills occurred, resulting in the dumping of 54,000 barrels of oil, according to the Department of Transportation. This latest breach, while considered relatively small, raises new questions about the proposed Keystone XL pipeline extension and whether President Obama should approve it.

　　It would carry 800,000 barrels a day of diluted bitumen crude over 1,700 miles, from the tar sands of Western Canada to refineries on the Gulf Coast of Texas. Environmentalists worry about potential spills, ruptures, and higher gaseous emissions from the use of tar sands oil. TransCanada Corporation and others have been awaiting approval for four years to move ahead with the project. A final decision from the president is expected this summer.

　　We examine some of the questions raised in the wake of this spill with Anthony Swift, an attorney who closely follows pipeline safety for the National—I'm sorry—Natural Resources Defense Council, or NRDC. And Andrew Black, he's the president of the Association of Oil Pipe Lines.

　　For the record, BP is a member of that group and a NewsHour underwriter.

　　Welcome to you both.

　　So, Andy Black, let me start with you. How serious is this pipeline rupture near Little Rock?

　　ANDREW BLACK, President, Association of Oil Pipe Lines: Well, no matter how rare a pipeline accident is, you don't want to see a scene like that.

　　What an operator wants to do is respond quickly, clean up, and try to learn the cause. As you said, we don't know the cause yet. He wants to share that that information to continue improving the safety records of pipelines, which are the safest method of transporting crude oil.

　　JUDY WOODRUFF:Anthony Swift, how serious do you think this particular incident is?

　　ANTHONY SWIFT, Natural Resources Defense Council: Well, this was a spill of up to 200,000 gallons of tar sands crude.

　　We saw it going through a suburban community in Arkansas. It's a very serious spill. EPA considers it a serious spill. And, you know, frankly, we have found that with tar sands spills, these are spills that are more difficult to clean. A similar spill in Kalamazoo, Mich., became the most expensive onshore pipeline spill in history, much because of the unique behavior of tar sands when it spills.

　　JUDY WOODRUFF:Well, what are you saying, that there's something particularly complicated about this kind of oil?

　　ANTHONY SWIFT:That's exactly right. The tar sands crude is a crude that has not—is not similar to the crudes historically moved on the U.S. pipeline systems. It's basically a mixture of very thick bitumen, which is solid at room temperature, and volatile petrochemicals that are very toxic once they reach the air.

　　And once spilled, you have a gas-off of the petrochemicals that expose residents to toxins and the bitumen itself then becomes heavier. If it reaches a water body, it flows underneath it. It's hard to control.

　　JUDY WOODRUFF:Andy Black, how much more complicated, how much riskier is it to be sending this kind of bitumen crude across the country?

　　ANDREW BLACK:It's no more complicated, Judy.

　　And U.S. pipeline incident records show that. With more than 40 years of moving crude oil from the Canadian oil sands, there's not been one pipeline accident in the United States caused by that and—caused by the type of crude from the Canadian oil sands. And the Department of State, when they have been exhaustively reviewing the Keystone XL pipeline, have similarly found that there are no more corrosive elements of crude from Western Canada as there are from California, Venezuela, Mexico. Crude has been safely moved for decades.

　　JUDY WOODRUFF:So, if it's the case, why the additional concern on the part of environmental groups?

　　ANTHONY SWIFT:Well, it's simply not true.

　　We saw with the Kalamazoo spill, 800,000 barrels—gallons were spilled from external corrosion. We don't know what caused the Pegasus spill, but we do know that pipelines moving tar sands-diluted bitumen have had poor safety records. And, as an example, the first shipments that came into the U.S. came in the late '90s into the Northern Midwest.

　　Those pipelines now over the last three years have spilled 3.6 times as much crude oil per pipeline mile as the national average.

　　JUDY WOODRUFF:And, in fact, we were seeing, Andy Black, as we have just reported, 364 spills or ruptures in the country last year, and you just heard that number of just this particular kind of tar sands crude. It sounds like what the two of you are saying doesn't reconcile.

　　ANDREW BLACK:Well, two things.

　　First, I would like to put that number in context. The 54,000 barrels spilled last year, that's out of 11.3 billion barrels of crude oil moved safely last year, crude oil and refined petroleum products, a reliability record that's 99.9995 percent.

　　As to the accident in Michigan, as Mr. Swift mentioned, that it was an external corrosion-caused accident, which the National Transportation Safety Board said had nothing to do with the type of crude that it was carrying.

　　JUDY WOODRUFF:External corrosion meaning the outside of the pipeline, rather than what was flowing through it?

　　ANDREW BLACK:Exactly.

　　If there was a problem with Canadian oil sands with corrosion, it would have caused an internal corrosion accident, and it didn't. And no pipeline accidents from internal corrosion have occurred on pipelines carrying that crude from Canada.

　　JUDY WOODRUFF:What about that? Because that bears directly on what might happen with the Keystone pipeline.

　　ANTHONY SWIFT:That's right.

　　And we know small set of California pipelines that higher-temperature pipelines spill more frequently due to external corrosion than conventional pipelines. If they're over 100 degrees, they spill up to 23 times as often due to external corrosion.

　　JUDY WOODRUFF:So you're saying what is going through the pipeline affects what's happening outside of it?

　　ANTHONY SWIFT:Around the pipeline.

　　ANDREW BLACK:If you look at the State Department study, not ours, the State Department's, they say you need to look at that California study with caution. Those are different design characteristics on a pipeline.

　　Again, no accidents on U.S. pipelines carrying oil sands crude caused by oil sands crude.

　　JUDY WOODRUFF:He's stating that as a fact.

　　ANTHONY SWIFT:And it's not.

　　The NTSB didn't say that the conditions under which the pipeline was operated based on what the crude -- what crude it was carrying had nothing to do with the accident. It just didn't weigh into it. And the State Department hasn't studied this issue. Pipeline regulators have said that they haven't studied this issue.

　　In fact, the head pipeline regulator told Congress in 2011 that her agency couldn't guarantee that regulations were strong enough for diluted bitumen pipelines.

　　JUDY WOODRUFF:All right, do you want to respond to that?

　　ANDREW BLACK:I'm not going to disagree with the chairwoman of the National Transportation Safety Board.

　　And this issue is being studied right now by the National Academy of Sciences. If it's done fairly, as I believe it will be, it will show what the decades of experience have showed us, that there's not a concern for corrosion. It's no more corrosive than any heavy crude.

　　JUDY WOODRUFF:Some people look at what's happening with the pipelines that run across this country and say it's inevitable that they're going to be some spills, some ruptures. It's just by the very nature of what's going through these lines.

　　ANTHONY SWIFT:Look, we have seen—I mean, the question is, are the risks worth the benefits?

　　You take a look at Pegasus and Keystone XL. Pegasus is a pipeline with a 10th of the capacity of Keystone XL. You build Keystone XL, you have a more significant—a 10 times more significant risk if there is a spill. And the question is, what is the benefit to the U.S. public?

　　You're dealing with a low-quality crude that increases climate emissions well above conventional crude, has increased risk to U.S. water bodies and communities, and is meant to go through the U.S. in order to bring tar sands to Gulf Coast refineries which are now exporting over three million barrels a day of refined products.

　　JUDY WOODRUFF:So he's making the argument for—I mean, against the XL—the Keystone XL pipeline, for expanding it.

　　ANDREW BLACK:We have not reached the goal yet of zero pipeline accidents. The industry works hard for that. The safety record has improved.

　　Over the last 10 years, the number of accidents per miles of pipe has dropped 60 percent. The industry spent $1.1 billion dollars in just 2011 on this. It continues to work every day on this.

　　JUDY WOODRUFF:Making safer pipelines? Working on the oil? How? How are they safer?

　　ANDREW BLACK:We—we're building pipelines today safer than ever before using modern techniques, modern coating, modern welding practices.

　　And that's what Keystone XL Will have. But, also, the technology is improving to inspect pipelines and learn more about what is happening. Now, all—all of that is contributing to, again, that 60 percent drop in accidents over the last 10 years.

　　JUDY WOODRUFF:Is either—go ahead.

　　ANTHONY SWIFT:Well, I was just going say just take a look at TransCanada's first pipeline, Keystone one in the Midwest. It was a new pipeline in 2010 and it spilled 14 years—in its first year of operation and had to be shut down by federal regulators.

　　ANDREW BLACK:It has had a couple of accidents at facilities.

　　The pipeline right of way has never been affected. The integrity of that pipeline has not been found at fault yet. I would like that add, as you were mentioning, about Keystone XL, and Anthony, the pipeline should be considered as an alternative to other modes of transporting crude oil, which our country needs, that can move on rail, truck, barge.

　　Nobody disputes that pipelines are the safest method. So if we're going to be bringing those barrels of crude oil into the U.S., it should be on a pipeline.

　　JUDY WOODRUFF:We're going to leave it there.

　　Anthony—Andrew Black, Anthony Swift, thank you.

　　ANTHONY SWIFT:Thank you, Judy.