Near-miss: Divers nearly hit by weight on taut wire

IMCA has received a report of a near-miss incident wherein a taut wire weight narrowly missed two divers before coming to rest next to a subsea structure. There was no injury to the divers nor damage to the structure.

In undertaking its work, the DP vessel had moved, resulting in the taut wire running above the divers and the subsea structure. The dive was being run by a trainee diving supervisor under the direction of an experienced diving supervisor. The DP operator (DPO) was a deck officer experienced in DP operations. Communications were through an open communication system between the bridge and dive control.

The divers were in the process of recovering tools to clear the worksite prior to relocation of the vessel. Bridge and dive control had agreed that the vessel would need to move to re-plumb the taut wire prior to recovery. Dive control stated that a move of approximately 15 metres was required to re-plumb the taut wire. The vessel moved 5m, after which the DPO announced that he was ‘going to lift port taut wire’, believing that the taut wire weight could be recovered clear of the divers and the subsea structure. At the end of this announcement from the bridge the trainee diving supervisor said ‘OK’ on the open communications channel, but in response to another conversation. The DPO on the bridge interpreted this as an okay to lift the taut wire. The experienced diving supervisor immediately called an ‘all stop’. However, the lift had already commenced and although the bridge stopped the lift there had been nine seconds of lifting, which was sufficient for the taut wire weight to swing towards the subsea structure and the divers.

The investigation identified the following two main causal factors:

• There was a failure in communication protocol between the bridge and the dive control;
• Although the DP operator was experienced, he was experienced in DP operations on lay vessels rather than on dive support vessel.

The following remedial actions were recommended:

• Reinforcement of correct ‘repeat back’ protocols to be carried out. ‘OK’ is not a sufficient response to a critical operational question. The correct response should include confirmation that the ‘OK’ is in relation to the question asked, e.g. ‘OK to lift the taut wire’ or ‘OK to move vessel’;
• Review of the familiarisation process to identify gaps in knowledge when personnel are relocated from one area of operations to another;

Guidance on operational communications contains useful references to publications regarding correct radio procedure.