Alexis Linder and Curran Bullock walk along a trail near Spring Branch in Tysons Corner. Residents have organized a coalition to oppose a highway ramp that could go through the wooded area. (Shamus Ian Fatzinger/Fairfax County Times)

Fifteen neighborhood associations in the Tysons Corner area are working together to persuade Fairfax County not to build a highway ramp that would cut into a stream valley.

The coalition, Save Tysons Last Forest, has been lobbying officials and collecting petition signatures to oppose the road.

Fairfax transportation staff members have been evaluating the ramp option as a way to alleviate traffic as Tysons continues to grow. The plans for Tysons adopted in 2010 included a new street grid with three potential new connections to the Dulles Toll Road.

One of the three, west of Route 7, commonly is referred to as the Boone Boulevard extension. It could go through a stream valley park to connect the new road to the Dulles Toll Road, or there could be ramps snaking around the existing Sheraton hotel.

The county is analyzing the Boone Boulevard extension and the two other possible ramp connections, looking at transportation benefits, as well as potential environmental and other effects, Department of Transportation director Tom Biesiadny said.

“It’s a very high-level feasibility study,” he said. The ramps, if built, would not be completed for decades.

Members of Save Tysons Last Forest are making several arguments against the possible extension and hoping to get the option removed from consideration.

“It’s amazing how quickly the community came together,” said Pam Konde, president of the Greater Tysons Green Civic Association, which has about 350 members. “Now, everyone is sort of playing the role of the Lorax.”

The Old Courthouse Spring Branch property is owned by the Fairfax County Park Authority. The group thinks the land has several layers of legal protection, starting with covenants on the deeds from when the previous landowners granted the land to the county, which state that it is to remain as parkland.

In addition, the land has a “resource protection area” designation, which is designed to protect water quality by limiting development in flood plains and stream valleys. Also, the county’s comprehensive plan for Tysons contains language about protecting stream valley parks.

The forested area serves as an important buffer between the commercial part of Tysons and the residential area, said Konde and Dean Mason, a resident of the Ashgrove Estates community who is active in Save Tysons Last Forest.

“There is precious little green space that is remaining,” Mason said. “That buffer is going to become that much more important as the commercial sections of Tysons become more developed.”

The route that would have the most impact on the stream valley is not the only option. Therefore, Mason and Konde said, they have a hard time understanding why the county is considering damaging land designated for preservation.

“We are saying, ‘Take it off the table right now,’ ” Konde said. “It seems like an absolute waste of county time and money if they don’t believe it’s a viable option.”

Biesiadny said the county understands why the neighbors want to protect the land, adding that community input has been valuable to the evaluation process. The county likely will have public meetings this fall to update residents on the study, he said.

Ultimately, the Board of Supervisors will decide which ramp option, if any, to put into county transportation plans.

“Even after the board makes a decision, then we have to get into the formal environmental review process,” Biesiadny said.