Tara Lohan: Six Things You Need to Know About the Arkansas Oil Spill?

By now, you already know that at least 84,000 gallons of crude spilled from the Exxon Mobil pipeline, swamping an Arkansas subdivision on Friday, and causing the evacuation of 22 homes. In addition to the loss of wildlife, damage to property, and environmental and human health hazards posed by the spill, may have implications for the Keystone XL pipeline currently under consideration by the Obama administration. There is a lot more to the story that's important to understand. Here are the crucial things. Inside Climate News reported shortly after the spill, that an Exxon official confirmed the pipeline was transporting a heavy form of crude from the Canadian tar sands region. Specifically, it has been identified as Wabasca Heavy, Lisa Song writes, which is a type of diluted bitumen, or dilbit, from Alberta's tar sand region, although you won't hear any Exxon folks calling it tar sands. Dilbit is some seriously nasty stuff. She writes about a previous dilbit spill by Enbridge in Michigan's Kalamazoo River in 2010: Dilbit is a mixture of heavy bitumen and diluents, light hydrocarbons used to thin the bitumen, so it can flow through pipelines. While most conventional crude oils will float on water, the bitumen began sinking into the river as the diluents evaporated, leaving a sludge of submerged oil, that defied traditional cleanup methods. Earlier this month, the EPA ordered Enbridge, Inc., the Canadian company that owns the pipeline, to dredge sunken oil from the riverbed. The cleanup has cost more than $820 million to date, and could top $1 billion, once the order is carried out. The Arkansas spill wasn't as big as the Michigan spill, and it was farther from main water bodies, but it's still serious business. If you want to know more about how dangerous tar sands dilbit can be, the Dilbit Disaster is a must read. The Pegasus pipeline, running more than 850 miles between Patoka, Illinois and Nederland Texas, is 20 inches in diameter, and was built in the 1940's, to carry crude from Texas to Illinois. But in 2006, the flow was reversed, in order to help relieve the tar sands crude bottleneck in Cushing, Oklahoma, the same reason given by proponents for the construction of Keystone XL. The pipeline was built to carry 65,000 barrels a day, but Exxon was allowed to expand that to 95,000 barrels a day, just a few years ago. All of these facts bring up some basic questions. What effect does a higher capacity have on the pipeline? And what effect does switching from conventional crude to dilbit have on the pipeline, considering it was built to have a much thinner crude flowing through it?