By Dave Levitan
Details are still sketchy on exactly how an oil pipeline buried under the Yellowstone River in Montana ruptured and spilled at least 42,000 gallons of oil, but indications so far point to river flooding as a likely contributing factor, revealing a largely unaddressed climate-related risk to energy infrastructure.
Jim Swanson surveys the oil impact on his property in Laurel, Mont., on July 4, 2011. A pipeline near Laurel, Mont., ruptured and spilled an estimated 1,000 barrels of crude oil into the Yellowstone River last weekend. Credit: Jim Urquhart/AP Photo.
The river level, running well above flood stage, may have scoured the riverbed and exposed a pipeline, operated by Exxon Mobil Corp., that was supposed to be buried more than five feet out of harm’s way. Once it was exposed, any debris carried along by the river could have struck the pipeline and caused the leak. The immediate question arises of how likely such an event may be at the thousands of other pipeline river crossings around the country. And with climate change likely playing a role in changes to extreme weather events like those that have caused flooding through the first half of 2011, some experts say a warming climate could be putting pipelines at higher risk for more accidents like this one.
“I think that the Montana Yellowstone River oil spill has been a warning about what floods can mean for pipelines, even when they are buried deep under a riverbed,” said Susan Casey-Lefkowitz, director of the Natural Resource Defense Council’s International Program.
“We need to take a hard look at our pipeline safety regulations, we need to update them, we need to take new information into account… and [that includes] things like the effects of climate change on infrastructure, and that’s not something that we had been talking about yet.”
There have been suggestions in the past that flooding, and changes to flooding frequency and severity, could affect pipelines, but analyses of the risk are lacking. Hurricanes Ivan, Katrina, and Rita reportedly damaged hundreds of pipelines, but those are on the seabed in the Gulf of Mexico; one study using unique measurements during Hurricane Ivan showed that the wind and waves caused severe stress to the seabed, and the stress lasted for a week after the storm passed through.
And of course, if hurricanes grow more severe as the climate warms, as some studies indicate, then the risks to those pipelines could increase as well.
River flooding in particular is largely absent from energy infrastructure risk assessments. One report by the California Energy Commission stated simply that: “altering patterns of precipitation that increase [flash flooding] events could result in a greater number of pipeline service disruptions.” Another publication by the National Research Council noted that pipeline regulations required a minimum of three feet of cover over a buried line, and that “intense precipitation can erode soil cover…. Scour and shifting of pipelines are a major problem in shallow riverbeds, where pipelines are more exposed to the elements.”
Extreme precipitation events becoming more frequent
It is notable that in the Yellowstone River where the most recent accident occurred, the flooding was not a particularly extreme or rare event. According to John Kilpatrick, director of the U.S. Geological Survey’s Montana Water Science Center, these flow rates in the river tend to occur once every 10 to 25 years. For comparison, the massive Mississippi River flooding earlier this year was closer to a 500-year event (its second since 1993, incidentally).
And there is now reasonable evidence that conditions conducive to the kind of floods that have ravaged rivers from the Mississippi to the Missouri and the Yellowstone this year may become more and more common as the climate warms. In fact, scientists have already linked greenhouse gas emissions to changes in extreme precipitation events.
Two papers published in the journal in February tied higher levels of greenhouse gases in the atmosphere to the observed trend of more intense rainfall events in much of the Northern Hemisphere. One of the studies found that emissions of greenhouse gases significantly boosted the odds of a particularly destructive flooding event in the UK in 2000.
Francis Zwiers, a climate scientist and director of the Pacific Climate Impacts Consortium, has published several papers showing that extreme precipitation events will become more frequent over the course of the century.
Visible satellite image of Hurricane Ike as it approached the Texas coast on the morning of September 12, 2008. Seafloor oil and gas pipelines are overlain in brown. Credit: SkyTruth.org/flickr.
“Physically that makes lots of sense, you’ve got the warmer atmosphere, the warmer atmosphere can hold more moisture,” Zwiers said. “It doesn’t necessarily mean that it is going to rain more in any given location… but if there is more moisture available, then extreme events should become more extreme, and that’s exactly what we see in the models.”
Zwiers told Climate Central that comparing data from a number of climate models has suggested that a 100-year event in North America — meaning, a rainstorm of a severity that has a one percent chance of occurring in any given year — will become closer to a 70-year event by the end of the 21st century. A 50-year event will turn into a 25-year event, and as he and his colleagues showed in a paper in the Journal of Climate in 2007 a 20-year event will become a seven to 10-year event. This suggests, Zwiers said, that river flooding could become more common as well.
“So it means if you have designed infrastructure that will protect up to what you perceive today to be a 100-year event, that protection might not be quite as strong in the future,” Zwiers said. “You’ll have to deal with damages from excess water flow and so on more frequently.”
An increased risk of flooding also means an increased risk of exposed pipelines. “With higher flows you are more likely to have enough velocity to pick up and move sediment around,” said the USGS’ Kilpatrick.
Focus on oil and gas pipelines
Pipeline safety has jumped into the fore of energy conversations in the last year or so, beginning with a large oil spill into the Kalamazoo River in Michigan. That spill apparently also occurred when the river was above flood stage levels, though there is no indication that the flood itself caused the spill. There is also an ongoing controversy surrounding the Keystone XL pipeline, a huge project designed to bring tar sands oil south from Alberta to Texas.
“Keystone XL will cross rivers throughout the United States,” Casey-Lefkowitz said; this includes the Yellowstone, where the spill cleanup is ongoing. Her organization, the NRDC, has joined many other groups in opposing the pipeline; a final environmental impact statement is expected from the State Department this summer. “Right now TransCanada, the company that has proposed it, is saying that under the Yellowstone river it will be buried twice as deep as the Exxon pipeline was, but that’s not necessarily the case under all the rivers [the pipeline will cross].”
And though high profile spills like that in the Kalamazoo make the news, pipeline incidents have long been common events. The Office of Pipeline Safety – part of the Department of Transportation – has recorded an average of 282 “significant” incidents each year since 1991, with little signs of safety improvement over time. Will energy and pipeline companies take a changing climate into account in the future? For its part, Exxon Mobil — owners of the Yellowstone River pipeline that ruptured – isn’t ready to commit.
A spokesperson for Exxon Mobil, Kevin Allexon, told Climate Central in an e-mail that the company is “determined to learn from this so we don't repeat [it],” but refused to answer questions specifically related to climate change, calling them “speculative.”
The oil carried by the flood waters at least 100 miles downstream from the Yellowstone spill is real enough, and the increased likelihood of extreme precipitation events as the climate warms suggests it won’t be the last such incident. As Kilpatrick, of the USGS, pointed out, “rivers are powerful things. If you put your infrastructure in the way of it, at some point, at some time, the river is probably going to have an impact on it.”