From the Arizona Cardinals home page:
The 152,000 square-foot concrete stadium floor will have a utility grid embedded in the floor and can host various events like trade and consumer shows, conventions, concerts, motor sports and rodeos.When the Cardinals are playing poorly, fans should be allowed to press the button the ejects the field and teams out of the stadium.
The grass field remains outside the stadium in the sun until game day getting the maximum amount of sunshine and nourishment, eliminating humidity problems inside the stadium and providing unrestricted access to the stadium floor for events and staging.
The tray will take approximately 45 minutes to move. The tray will rest atop tracks and will roll out on steel wheel sets powered by small electric motors.
The field will support approximately 94,000 square feet (over 2 acres) of natural grass. Having the rollout field saves $50 million in costs since it is more economical to move the field than having the entire roof retract to allow the necessary sunshine to reach the grass.
The natural grass playing surface is contained in a retractable, 12-million pound tray that will be 234 feet wide by 400 feet long, the first of its kind in North America.