An estimated 2,000 barrels of tar sands oil originating from Alberta, Canada, spilled from a ruptured pipeline owned by U.S. energy giant ExxonMobil over the weekend in Mayflower, Ark., a town of a population of around 1,700 people, forcing the evacuation of 22 homes. ExxonMobil sent emergency cleanup crews to contain the oil leakage, and has offered to pay all of the cleanup costs associated with the event.

The Mayflower oil spill has cast a shadow over the controversial plan to construct the Keystone XL pipeline. Exxon’s Pegasus pipeline, the pipeline that leaked this weekend, runs from Patoka, Ill., to Nederland, Texas, covering a distance of 848 miles. The Pegasus pipeline carries over 90,000 barrels of crude oil.

ANALYSIS: The Sticky Problems With Tar Sands

Compare that to the proposed Keystone pipeline system, which would, by contrast, when fully completed transport over 800,000 barrels of crude oil along a 1,353 miles. Of that distance, 1,086 of those miles would be in the United States, according to the Congressional Research Service (PDF).

Like the Pegasus pipeline, the Keystone pipeline runs along residential communities and even rural and agricultural areas that have voiced concerns about the potential for an oil spill and the damage that could result from it. Given the weekend’s events, those concerns appear to be well-founded. Although it did affect several homes in the area, containment crews and local officials have reportedly assured the public that they’ve been able to prevent oil from reaching Lake Conway, which could have posed a risk to the water supply around Little Rock, Ark. (Some local wildlife in the area, however, haven’t been spared, as noted by TreeHugger’s Chris Tackett.)

But how common are oil spills in or around residential communities?

ANALYSIS: How to Become a Citizen Climate Scientist

As noted by PBS’s the News Hour, 364 pipeline spills occurred in the United States last year, spilling an estimated 54,000 barrels of oil. Most of those incidents are small in scale, occur in remote areas, and are able to be contained quickly.

Oil spills of the magnitude seen in Mayflower are uncommon, but they can be devastating. The Environmental Protection Agency (EPA) has classified this incident as a “major spill.” There have been other, similar incidents over the years, however.

Last year, a half-century-old pipeline running along Washington County, Wisconsin, ruptured and leaked nearly 55,000 gallons of gasoline within a matter of minutes, as reported by the Milwaukee Journal-Sentinel. The spill contaminated local water supplies, compelling the state government to issue an advisory. Following the spill, attorneys representing local residents raised questions about the safety of the pipeline given its age and construction techniques used when it was built.

One of the largest and most devastating residential spills to occur in the United States somewhat recently happened in 1999, when a ruptured pipeline leaked some 270,000 gallons of liquid petroleum into an area surrounding the city of Bellingham, Wash. The gas created an explosive environment, as explained the the Department of Ecology of the State of Washington, which ignited and claimed three lives.

Some spills might be caused by equipment failure or operator error, but others could also be created as a result of excavation work by third parties. In 2011, a bulldozer in Nemaha County, Nebraska, collided with an oil pipeline, causing over 119,000 gallons of oil to spill.

Tar sands spills are especially difficult and expensive to clean up. In 2010, a pipeline bearing heavy crude oil originating from Canada ruptured near the small town of Marshall, Michigan, spilling an estimated 819,000 of oil into Talmadge Creek, which flows into the Kalamazoo River. As the EPA notes in its report following the spill, oil was carried as far as 35 miles downstream. Cleanup costs climbed past three-quarters of a billion dollars.

The toll taken by this oil spill, after cleanup efforts have completed and damage checks have been cashed, remains to be seen. What is certain, however, is that with the decision over the expansion of the Keystone pipeline system looming for this summer, this oil spill will affect the conversation over whether the project is worth the costs.

IMAGE: Tar sands oil seeps into the ground of marshland in Mayflower, Ark. (NWFBlogs/Flickr)