Courtesy of the Bike Arlington blog:
"The Custis Trail will be closed for a probable 3 days starting 6/19/12 between the Lyon Village Shopping Center and Cherry Valley Park (near Quincy St) for the purpose of repaving. The detour is expected to utilize Quincy Street and Lee Highway to navigate people around the Trail construction area. There are areas of Street construction on both Quincy and Lee Highway so use extra caution in these areas. Detour signs will be posted. Commuters should allow themselves extra time to get to their destinations. Thank you for your patience while we make improvements to our trail system.

--Katie