The federal government is being asked to pay half the cost, and the state has agreed to pay one-quarter, mostly using Dulles Toll Road fees.
Fairfax County is supposed to pay the rest.
The fact that commercial landowners are paying the county's share has been touted as a cost savings for most Northern Virginians. Commercial property owners in the tax district have agreed to pay an extra 22 cents per $100 of their real estate value this year and similar amounts in the coming years.
County officials had looked at a sales tax and other ways to raise money. But the landowners in the tax district, most of whom signed a petition in favor of the rail tax, are carrying that burden.
"It is a unique way to finance the local share without putting the burden on the local taxpayers," Fairfax Board of Supervisors Chairman Gerald E. Connolly (D) said. He added that building densely around the Metro stops makes sense because it will help "build ridership" for the new line.
In return for their tax money, major employers will gain rail's convenience on behalf of their customers and employees. And many of the landowners with property near one of the four proposed stops will realize substantial increases in the amount they can build -- once the rail project is funded or built.
The so-called "density triggers" in the county land plan, which allow more development around rail stops, date to planning amendments drafted in 1994 and 2001. The development bonuses for property near a rail stop are large, sometimes roughly doubling the amount that can be built on a property.
Like the rail-dependent proposal to expand Tysons Corner Center, a Lerner Enterprises proposal to build eight towers nearby, approved in 2003, similarly depends on the construction of rail. Some of the towers could be as tall as 30 stories.
Even with the bonus for rail, the permitted building density in Tysons Corner falls short of what is permitted in Ballston, Bethesda and parts of downtown Washington.
But more recently, amid the renewed enthusiasm for rail, developers have asked for permission to build even more if the rail line comes. They have filed 21 requests for changes to the Tysons Corner land plan.
Given the swell of development proposals, several opponents have asserted that the rail project is meant to assist developers, not commuters.
"Do developers benefit? Sure," said John McGranahan, an attorney for the landowner group that set up the tax district. "But some of the biggest proponents of the tax district were employers -- like Gannett and Capital One -- and retailers, not just developers. The opponents of this project have characterized this as a developer's deal. But that's flat wrong. It's a great deal for the citizens."
The tax district reflects a growing movement for private groups to pitch in to create transportation solutions.
The idea for the tax district arose out of a similar effort in the late 1980s to pay for the widening of Route 28. Owners of property there, frustrated by the lack of state transportation spending on the roadway, agreed to create a special tax district to help pay for most of the roadwork.
While proponents tout the tax district for Tysons rail as a model that might be used elsewhere in the country, it also has been a frequent source of instability in the political coalition that came together to push for the rail project.
Property owners in Reston and Herndon objected to being included in the tax district, and in late 2003, organizers were forced to limit the tax district to properties only along the rail line's first phase.
Even then, some property owners subject to the tax have complained that they will derive little benefit from rail -- either because they are too far away from a station or because they have little incentive to build anything new on their properties. The owners of roughly 30 percent of the assessed value of the land in the tax district did not sign the petition.
Moreover, as rail organizers pursue the second tax district in Reston and Herndon to help pay for the second phase of the rail project -- which would take the line through Reston to Dulles International Airport and beyond -- the opposition continues, and organizers have fallen behind their self-imposed deadlines.
"We're waiting for additional information," said Peter Johnston, a senior vice president at Boston Properties, and one of the organizers of the second taxing district. "I'm optimistic that once we can get some answers that the support will be there. But we think it's prudent to wait."