Arlnow reports that the trail was moved to save some mature trees.
The trail is expected to cost about $1.7 million, according to county Dept. of Environmental Services spokeswoman Shannon Whalen McDaniel, but it has not been put out to bid yet. The trail has been approved and in planning stages for years, but its initial path would have necessitated digging up hundreds of mature trees.
This Saturday, the Arlington County Board is likely to approve a realignment of the trail to put it closer to Towers Park and S. Rolfe Street, north of Columbia Pike. If approved, the county would pay $8,000 to the federal government to acquire the easement for the trail. The trail will then be put out to bid. Construction is expected to begin next year and end by summer 2015.
Here are images of phase I under work back in 2009.