225 ILCS 710/45.09

In no case shall a cage, skip or bucket or other vehicle be lowered directly to the bottom of the shaft when people are working there, but such cage, skip or bucket or other vehicle shall be stopped at least 15 feet above the bottom of such shaft until the signal to lower farther shall have been given to the hoisting engineer by one of the people at the bottom of the shaft; provided, however, that this rule shall not apply to shafts of less than 100 feet in depth.