Because of the facade's intricate design, the tower's window cleaning rig took three years and $3 million to plan. The resulting design incorporates "a rectangular steel box the size of a Smart car" on the roof, which hoists a mast and a hydraulic boom arm. Sixty-seven sensors and switches are housed in the box. A window cleaning deck hangs from the hydraulic boom arm, supported by six wire-rope strands. The device was installed in April 2005 on of elevated steel track looping the roof of the tower. The rig snapped in a 2013 incident that trapped two window cleaners.