A proposed TransCanada pipeline would carry crude oil through six states on its way from Alberta, Canada, to Texas -- but an opposition movement in just one of those states could derail the whole project.

Lawmakers in Nebraska have introduced a series of bills that would make certain areas of the state off-limits to TransCanada and require the company to set aside $500 million to cover the costs of a potential oil spill.

The sticking point is the Keystone XL pipeline's planned route through the Sandhills of northwestern Nebraska and over the Ogallala aquifer, which provides 80 percent of the state's water for drinking and irrigation. A diverse coalition has formed out of fear that an oil spill could contaminate the aquifer.

TransCanada already has a pipeline that runs through the eastern part of Nebraska, crossing only a small portion of the aquifer. There was almost no opposition to that pipeline when it was built two years ago, both because of its lower-risk location and because that was before the 2010 BP disaster in the Gulf of Mexico drew national attention to the catastrophic consequences of oil spills.

It's a different environment than it was even a couple of years ago, Mike Flood, the speaker of the Nebraska legislature, told NPR.

Diverse Coalition

The coalition against the new pipeline includes Nebraskans of all political and economic stripes, from conservative farmers to liberal environmentalists. The message that unifies them is simple.

Many Nebraskans, including myself, support the pipeline, but we are opposed to the route that goes through the Sandhills and over the Ogallala aquifer, Gov. Dave Heineman told NPR. We ask, why would you risk an oil spill or leak over the aquifer when TransCanada already has a pipeline route on the eastern side of Nebraska?

The $7 billion pipeline would also cross Montana, South Dakota, Kansas and Oklahoma on its way to oil refineries along the Gulf Coast in Texas. Nebraska is the only state that is putting up a significant fight, but it has gained supporters nationwide. Thousands of people surrounded the White House on Sunday to protest the pipeline.

TransCanada officials acknowledged the possibility of an oil spill or leak but said it was an unavoidable risk.

Anybody who looks at this objectively knows that we're decades away from being able to turn off a fossil fuel switch and flip on an alternative energy switch without affecting our quality of life, TransCanada spokesman Shawn Howard said.

Howard said that the company would reduce the risk as much as possible with state-of-the-art safety systems, but that it was impossible to reroute the pipeline at this point because the project is already three years into the federal approval process.

Supporters of the pipeline as currently planned point out that numerous pipelines already run across the Ogallala aquifer.

The pipeline is intended to reduce the United States' dependence on oil from the Middle East and Venezuela, and TransCanada estimates that the construction process will create 20,000 jobs through 2012.