Near miss: Unidentified differential pressure led to diver’s umbilical getting trapped

The incident occurred when two divers were working on some underwater clamps associated with two chlorination dosing lines on either side of the entrance to a gravity fed seawater intake located in a culvert.

Each of a number of culverts at the location contained a seawater intake fitted with an automated grating and trash cleaning system recessed 5m from the main opening. The diving operation necessitated moving repeatedly back and forth across the 5m wide intake opening between the clamps. This allowed some slack to be unintentionally introduced into the divers deployed umbilical.

After an extended period of incident free operations, one of the divers’ umbilicals became entrapped with the automated trash cleaning system, resulting in the diver being pulled towards the intake. The 2nd diver cut the umbilical to facilitate escape and both divers ascended to the surface in a controlled manner without injury.

Our member’s investigation revealed the following:

• The presence of an automated trash removal system was not communicated by the asset owners to the project team.
  
  
• As a consequence of this omission there was no system in place to ensure the automated trash removal system was effectively isolated.
  
  
• There was a “lock out/tag out” system in place for the seawater intake valves.
  
  
• The project risk assessment was not effectively reviewed on site to identify appropriate controls for site-specific hazards.
  
  
• The position of the dive tender was not relocated as the dive progressed across the face of the multiple intakes, meaning that excess umbilical was deployed in the water, increasing the potential for snagging.