An abandonment program was underway on the platform of an offshore drilling rig. The casing strings had been removed from the platform caisson, leaving five 20 inch-diameter conductor pipes. The first of the conductor pipes was raised to the rig floor. A floorman and assisting roustabout were asked to cover the opening (slot) in the platform cellar deck left by the removal of the conductor pipe.
The workers located a hole cover about the right size and proceeded to manually move it to cover the slot. Despite being unsecured, however, the cover was being used on another opening, which was then exposed. The floorman stepped into the newly exposed opening and fell 15.5 metres into the platform caisson. He received serious but, fortunately, non-life-threatening injuries including a dislocated ankle, fractured arm, two microfractures of the spine and a fractured sternum, as well as bruises and abrasions.