On March 29, the Pegasus oil pipeline, owned by ExxonMobil, ruptured in an upscale suburb of Little Rock, Ark. While the 5,000 to 7,000 barrel oil spill is dwarfed by the Deepwater Horizon spill from just a few years ago, it nonetheless raises serious questions about the safety of the large network of pipelines that crisscross the United States. This is especially in light of the particularly hazardous nature of the diluted bitumen oil—which is refined from tar sands found at the Athabasca Oil Flats in Alberta, Canada—that traveled through the Pegasus pipeline and will travel through the proposed Keystone XL pipeline.

Thus far, Arkansas has been lucky—no significant amount of oil has been found either in the nearby Lake Conway or in Lake Maumelle, which is a main source of drinking water for Little Rock. Exxon has certainly not helped its cause, however: it recently announced that it will discontinue temporary housing assistance to the families that lived in the 22 homes that had to be evacuated as a result of the spill.

The recent business practices by oil companies with regard to oil spills, in addition to the particularly hazardous materials being carried in the newly proposed Keystone XL pipeline, should raise serious concerns. Over the last 10 years, an estimated 3.5 million gallons, or about 83,000 barrels of oil, were spilled from oil pipelines each year. The kind of oil carried in the Pegasus pipeline and the proposed Keystone XL pipeline contains additives that evaporate and then contaminate the air. The diluted bitumen oil not only pollutes the groundwater, but also has the tendency to sink to the bottom of large bodies of water, making it very difficult to clean up.

To make matters even worse, the proposed Keystone XL pipeline would not only be about six times bigger than the Pegasus pipeline, delivering almost 600,000 barrels a day to Gulf refineries, but it would also pass through the Ogallala Aquifer. It is the largest aquifer in the United States, the source of drinking water for more than 2 million people and the main water source for many Midwestern farmers.

Beyond the potential risk of even the best-maintained pipelines spilling the oil they transport, modern oil companies, no doubt buoyed by their massive profits and recent American deregulation, have shown a serious disregard for the potential environmental impact that their mining and transportation operations can cause.

It is also worth remembering the Deepwater Horizon tragedy that, in addition to killing a large portion of the drilling team, led to the second-largest accidental oil spill in history and the largest accidental spill in more than 80 years. Increasingly, oil pipeline transportation, particularly of oil sands-derived bitumen, seems to be a terrible game of chance with each spill having the potential to affect hundreds of thousands, if not millions, of people. Thus far, we have largely been lucky—or at least ignorant of any such occurrences. The completion of the Keystone XL pipeline, however, would lead to a significant increase in the probability of a pipeline spill and a massive increase in its potential damage, in the process making large areas uninhabitable and unusable, both directly and through contamination of the water supply.