Photo by PoPville flickr user Mr. T in DC

From WMATA:

Metro will advance rebuilding efforts during off-peak hours Monday, June 25, through Friday, June 29, 2012.

Red Line
• Monday through Thursday, beginning at 10 p.m. each night, Red Line trains will single track between Judiciary Square and Rhode Island Avenue for cable replacement and DDOT bridge work. Customers should allow about 10 minutes of additional travel time.
• Monday and Tuesday, beginning at 10 p.m. each night, Red Line trains will single track between Friendship Heights and Medical Center for track circuit work. Customers should allow 15 minutes of additional travel time.
• Wednesday and Thursday, beginning at 10 p.m. each night, Red Line trains will single track between Twinbrook and Shady Grove for track circuit work. Customers should allow 15 minutes of additional travel time.

Orange Line: Monday through Thursday, beginning at 10 p.m. each night, Orange Line trains will single track between East Falls Church and West Falls Church for work associated with the Silver Line extension. Customers should allow 15 minutes of additional travel time.

Blue Line: Monday through Thursday, beginning at 10 p.m. each night, Blue Line trains will single track between Stadium-Armory and Addison Road for repairs to the “floating concrete slabs” beneath the rails. Customers should allow 15 minutes of additional travel time.