The Central Artery/Tunnel Project is one of the largest, most complex and technologically challenging infrastructure projects ever undertaken in the history of the United States, with one of the largest highway tunnel ventilation systems in the world.

Keystone was instrumental in the successful completion and start-up of this system, providing the transportation, rigging, assembly, alignment, and start-up of ninety-three centrifugal fans, six axial vane fans and thirty-two jet fans in addition to the erection of the structural steel plenum walls.