BSEE: Anchor-handling causes damage to subsea equipment and triggers gas release

The United States Bureau of Safety and Environmental Enforcement (BSEE) has published Safety Alert 508 on 30 September 2025, relating to a gas-release incident involving a dive support vessel (DSV) that was marking a pipeline ahead of a jack-up rig subsea well recompletion. The DSV was recovering two bow anchors from the seafloor.  

As the DSV approached the subsea well site, the vessel moved down-current, and the No. 1 bow-anchor wire became entangled in the well. The DSV backed away, but the wire remained snagged and multiple attempts to free it failed. During the final attempt, the wire caught the annulus-valve assembly, shearing several studs and detaching the valve from the tubing spool. A strong gas plume surfaced. The DSV retreated about 600m, and an emergency response began. During mobilization and execution of the emergency response, several critical preparation steps were overlooked:

BSEE identified the following findings (IMCA bold to highlight important issues)

• Planning and coordination were inadequate. The operator and contractor did not conduct simultaneous operations (SIMOPS) meeting or a hazard assessment.
• The Safety and Environmental Management System (SEMS) plan did not clearly specify which operations require SIMOPS planning and a hazard assessment.
• Communication between the DSV and the operator was lacking. Key personnel were not notified when the job began or what work was being performed.
• There was no anchor tug present which limited the vessel’s ability to hold position, increasing difficulty and risk.
• Information including drawings was not readily available during the emergency response.
• The replacement valve was not configured for diver handling, delaying efforts to secure the release.

To help prevent similar incidents in the future, BSEE recommends that operators and their contractors, where appropriate, consider the following:  

• Use a pre-job checklist that verifies all preparatory steps, including pipeline marking and weather or delay considerations.
• Establish contingency plans.
• Management of change: If delays occur (e.g., weather), reconfirm critical steps before remobilizing.
• Coordinate among internal teams and third-party contractors to ensure a shared understanding of job-readiness requirements.
• Hold a formal pre-mobilization review with all stakeholders to confirm scope, readiness and safety measures.
• Provide refresher training for personnel involved in offshore planning and execution to reinforce procedural compliance and communication.
• Ensure anchor-handling plans account for strong currents and vessel drift.
• Maintain clear communication with all stakeholders.
• Confirm that critical documentation is on board and accessible before mobilization.
• Include divers in preparation for subsea installation or repair activities.
• Review SEMS protocols to clarify SIMOPS and hazard-assessment requirements.