(Washington D.C. - David Schultz, WAMU) The construction of a subway line out to Dulles International Airport in Northern Virginia is one of the largest public works projects in the country, with a price tag of around $6 billion.

With that kind of dough, politics is bound to seep into the process one way or another. And it definitely has, especially after a decision yesterday that puts local politicians here in a no-win situation.

Yesterday, the Board of the Metropolitan Washington Airports Authority, which is overseeing the project, chose to locate the planned Metro station at Dulles underground, rather than above ground.

The Board made this decision against the advice of almost every elected official in the region - local, state and federal. That's because the underground option is more than $300 million more expensive than an above ground alternative.

Airports Board members said they chose the more expensive option because

it will be more convenient for passengers. Aside from the protection it provides them from the elements, an underground station would be much closer to the terminal, thus reducing the distance passengers will have to walk. Airports Board Member Mame Reiley said the above ground alternative would have been a "second-class station at a first-class airport."

But building a first-class station, which requires tunneling underneath an airport, comes with first-class bills. And the people paying those bills will be the aforementioned elected officials. Taxpayers in suburban Fairfax and Loudoun Counties, where the subway line would pass, are picking up a fixed percentage of the tab. The rest will come from a toll road that connects Dulles to D.C.

So the higher the cost of the project, the more local tax dollars will need to be spent on it. Furthermore, the more the project balloons in cost, the the higher tolls will have to rise. Both of these things will infuriate the constituents of elected leaders in the region. And elected leaders really, really don't like infuriated constituents.

Already, several have come out against it. The administration of Virginia Governor Bob McDonnell (R) expressed concerns. Fairfax County Chairman Sharon Bulova (D) told the Washington Post she wants the Airports Authority to pay for the extra cost of the underground station itself. Northern Virginia Congressman Frank Wolf (R) was more circumspect. "This is a bad decision," he said in a statement.

Ultimately though, this is a classic case of two groups with diverging, opposing interests.

The Authority's interest is to make Dulles a top tier airport, able to compete with the O'Hares, Hartsfield-Jacksons and JFKs of the world. Right now, Dulles' Achilles heel is its inconvenient location almost 30 miles outside of downtown D.C. The new subway line is supposed to remedy that, but if passengers decide the schlep from the subway station to the terminal isn't worth it, it will fail.

However, the interest of the elected officials is - wait for it - to get elected, and they can't do that in our modern Tea Party era if they appear to be spending tax dollars recklessly. So, with off-year elections just around the corner in Virginia, it's becoming politically advantageous to come out against this project. In fact, some local Supervisors in Fairfax and Loudoun have even grumbled about reneging on their counties' funding commitment, which would put the entire project in jeopardy.

Reiley, however, isn't worried about this. She says the Dulles rail project - and the supercharged development it will spur - is too vital to the economic futures of Fairfax and Loudoun for the Supvervisors to renege.

Also, Reiley says she's had private conversations with local Supervisors and they've told her they support the underground train station, but can't say so publicly. She says they'd prefer the unelected Airports Authority Board to make this tough decision, because "they have to run for reelection."

If that is the case, then a quote in today's Washington Post becomes very telling. Explaining why she's opposed to the underground station alignment, Bulova told the Post "We're looking out for our constituents."