Today, Amtrak revealed its new Union Station Master Plan. Currently at (and some might say beyond) its practical operating capacity, Union Station must be updated to accommodate the strong growth being seen in all transit modes, especially commuter rail and Amtrak.  The plan envisions a massive overhaul that will substantially improve connectivity to NoMa through construction of a monumental train shed on the northern side of the station.  The redeveloped Union Station will feature a green roof, ADA compliant platforms, underground parking and retail. As a result of this plan, the capacity of travelers using Union Station will triple and economic vitality will increase in and around the Washington Metropolitan Area.

http://www.amtrak.com/ccurl/919/171/Washington-Union-Station-Master-Plan-201207.pdf