Wash. Rev. Code § 49.24.260
All shafting used in pneumatic caissons shall be provided with ladders, which are to be kept clear and in good condition at all times. The distance between the centers of the rungs of a ladder shall not exceed fourteen inches and shall not vary more than one inch in any one piece of shafting. The length of the ladder rungs shall not be less than nine inches. The rungs of the ladder shall in no case be less than three inches from the wall or other obstruction in the shafting or opening in which the ladder shall be used. Under no circumstances shall a ladder inclining backward from the vertical be installed. A suitable ladder shall be provided from the top of all locks to the surface.
All man shafts shall be lighted at a distance of every ten feet with a guarded incandescent lamp.
All outside caisson air locks shall be provided with a platform not less than forty-two inches wide, and provided with a guardrail forty-two inches high.
All caissons in which fifteen or more men are employed shall have two locks, one of which shall be used as a man lock. Man locks and man shafts shall be in charge of a man whose duty it shall be to operate said lock and shaft. All caissons more than ten feet in diameter shall be provided with a separate man shaft, which shall be kept clear and in operating order at all times.
Locks shall be so located that the distance between the bottom door and water level shall be not less than three feet.
RCW 49.24.260