Even though the Exxon Valdez and Deepwater Horizon disasters have grabbed the headlines, oil spills hit land much more frequently, posing risks for lakes, streams and rivers.
That's especially true near pipelines, suggests a study in the current issue of the journal Risk Analysis that looks for places particularly vulnerable to inland oil spills across the Upper Midwest.
Despite the attention paid to the 2010 Gulf of Mexico oil spill disaster, which released about 4.9 million barrels of oil into the Gulf of Mexico, the majority of oil spills, about 60%, are inland ones. A 30-inch pipe rupture near Marshall, Mich., two years ago, for example, spilled about 19,000 barrels of crude oil into a creek and then the Kalamazoo River, stopping 80 miles short of Lake Michigan.
The problem is the plethora of "roads, railroads, pipelines, tanks" crossing some 10,851 watershed locales stretching from Minnesota to Ohio, each one a potential spill location, says EPA analyst Thomas Brody, who led the study.
"If you put them on the map, you can see the threats, but it's hard to aggregate them visually all together," he says, to weigh all the risks appropriately. That's partly because fisheries, drinking water sources, migrating birds and other environmentally sensitive spots that leaking oil might spill into aren't always readily apparent from a map. "Liquids like water and oil are going to move," notes the study.
So, in the study, Brody and colleagues combined federal watershed drainage maps, two decades of spill records and cleanup cost data to identify areas most vulnerable to inland oil spills. Essentially, these are spots where the combination of past spills, pipelines that crisscross sensitive wetlands and slow response times by cleanup crews leave these locations susceptible to considerable damage in the event of a significant spill.
The study focused on the Upper Midwest ("Region 5" in EPA-speak), otherwise known as the lake and river-filled states of Michigan, Indiana, Illinois, Minnesota, Ohio and Wisconsin. But the authors think their approach could be applied nationwide.
The data in the study showed that inland crude oil spills occurred way more often near small towns of fewer than 10,000 people, accounting for 77% of the spills, which might raise concerns about response times to accidents. The study evaluated several dozen "high-risk" watershed locations, rating them as two to five times as vulnerable to spills than the great mass of other watershed locations. "Mostly it is where there are pipelines," Brody says, not a big surprise.
So, what does the study tell us about places vulnerable to inland oil spills? A National Response Center database of voluntary reports by industries of spills that was used in the study suggests that about 87% of their risks came from pipelines and 12.2% came from nearby storage tanks. And in the end, most of the higher-risk locations were reachable by federal emergency response teams within six hours of a disaster. (Richard Karl, an EPA Superfund site official in the region, notes, however, that local officials most often respond to spills ahead of federal personnel.)