Marshall Islands Investigation Report: Mooring Failure After Overloading in High Winds


The Marine Administrator of the Republic of the Marshall Islands has released its investigation report into the Valaris DS-4 mooring failure at Hunterston Jetty on the Firth of Clyde, Scotland, during high winds on February 2 2021.

The Incident

BAccording to the Met Office Coastal Weather Forecast issued at 0001 UTC on 2 February 2021, the forecast for the next 24 hours indicated east to south-easterly winds between Beaufort Force 5-7 (17-33 kn) with periods of Beaufort Force 8 (34-40 knots). Forecasts issued later in the day called for easterly winds of similar strength.

According to the VALARIS DS-4 noon report of February 2, 2021, the winds observed were from the northeast at 25 knots with gusts between 45 and 53 knots. It was reported that the mooring lines and gangway were being checked due to the strong gusts and the drillship was being readied for the next few days of forecast high winds coming from shore.

The ENSCO DS-8 noon report indicated that easterly winds at 30-35 knots with gusts of 40-50 knots had been recorded. It was also reported that the mooring lines were adjusted as required and the No. 3 and No. 4 diesel generators were pre-heated.

According to drillship logs, wind speeds increased throughout the day. At 4 p.m., VALARIS DS-4 reported northeasterly winds of 50 knots. Storm-force winds continued, and by 6:30 p.m. winds were reported to be at 55 knots.

By 5:20 p.m., the ENSCO DS-8’s No. 3 diesel generator had been started and power to the drillship had been replaced with the portable deck generator.

Credit: Marshall Islands Maritime Administrator

At 6:45 p.m., the captain, C/E and duty ASD of the VALARIS DS-4 reported hearing a noise which they believed sounded like the anchor chain. The wind speed was reported to be around 70 knots47. When the master and the DSO came up on deck to investigate, they found that several forward mooring lines had separated and the drillship was moving away from the jetty.

The C/E of the VALARIS DS-4 went to the engine room to start a diesel generator and prepare thruster n°5.

Based on AIS information, around 1915 all forward mooring lines of the drillship had separated. Within 2-3 minutes the remaining mooring lines separated. The drillship was blown off the jetty and began to drift southwest at approximately 2 knots.

About the time the VALARIS DS-4 began to pull away from the pier, the master made an announcement over the drillship’s public address system ordering all crew members to assemble on deck . The C/E left the engine room and proceeded to the bridge.

It was reported that the diesel generator that the C/E had started stopped working shortly after he left the engine room.

At 7:15 p.m., the captain of the VALARIS DS-4 broadcast a MAYDAY on VHF.

According to AIS information, around 7:23 p.m., the anchor held. By this time, VALARIS DS-4 had drifted about halfway across the channel between the jetty and Great Cumbrae Island, which lay about 400m to the west.


VALARIS DS-4 lost its moorings and was carried off the pier when the recorded wind was from the northeast at 55 knots. It would seem that the speed was actually higher when the moorings started to separate. All mooring lines on the drillship separated within 30 minutes after the captain and other crew members reported hearing what they thought was the anchor chain at 6:45 p.m. on February 2, 2021. The vessel drifted halfway across the channel between the pier and Great Cumbrae Island before anchor. reset. The fact that the anchor held likely prevented the drillship from running aground on Great Cumbrae Island.

The C/E aboard the VALARIS DS-4 had started a diesel generator some time after the noise, believed to be the anchor chain, was heard. He had been unable to transfer power from the portable generator to the diesel generator and then bring one or more of the drillship’s thrusters online before the drillship was ejected from the pier or while it was drifting across the channel.

Credit: Marshall Islands Maritime Administrator

ENSCO DS-8’s mooring lines held the drillship to the jetty without any parting lines or assistance from the time the VALARIS DS-4’s mooring line began to part until a tugboat arrives and begins pushing the drillship against the jetty at 8:40 p.m. on February 2, 2021. One of the drillship’s diesel generators had been started and power to the drillship had switched from the portable deck generator at 5:20 p.m. on February 3, 2021, and at noon on February 4, 2021, three of the drillship’s thrusters were operating.

It cannot be determined whether the VALARIS DS-4 would have remained alongside the pier had the crew members been able to place two thrusters in line or if tugs had pushed the drillship alongside before 1845 on February 2, 2021.

It also cannot be determined whether ENSCO DS-8’s mooring lines would have held the drillship alongside the jetty without the use of thrusters or the assistance of tugs pushing the drillship up. ‘until the period of strong northeast to east winds has subsided. before February 6, 2021.


Causal factors that contributed to this maritime incident include:

  • The inability of the VALARIS DS-4 crew members to get the thrusters online in time to prevent the moorings from being overloaded by storm-force winds from the northeast; and
  • The captain of the VALARIS DS-4 did not request tug assistance when the weather forecast for storm-force northeast winds was received on the afternoon of February 2, 2021.

Other causal factors that may have contributed to this maritime incident include:

  • Inadequate coordination between Joulon and COL throughout the planning process for the decommissioning of VALARIS DS-4 and ENSCO DS-8 at Hunterston Jetty;
  • Inadequate identification and consideration of local conditions, including higher-than-expected northeast and easterly winds, winter temperatures, and the time required for tugs to arrive after being called, as part of the Joulon risk assessment for berthing drillships along Hunterston Pier;
  • Inadequate identification of drillship power requirements during Joulon and Noah’s planning for VALARIS DS-4 and ENSCO DS-8 commissioning to ensure sufficient diesel generators and thrusters would be available if needed during a period of high winds or an emergency situation;
  • The apparent deviation from the drillship mooring plans when VALARIS DS-4 and ENSCO DS-8 were moored after being moved along the pier in late January 2021;
  • The lack of third-party verification that VALARIS DS-4 and ENSCO DS-8 were moored in accordance with the drillship mooring plans;
  • With the exception of the drillship docking plans, the lack of third-party assurance of Joulon and Noah’s planning and execution of the decommissioning of the VALARIS DS-4 and ENSCO DS-8 at Hunterston Jetty ;
  • Lack of comprehensive flag state regulations to ensure the safety and security of decommissioned vessels;
  • The lack of flag state requirements for ships registered in the Republic of the Marshall Islands that are laid up to undergo inspections or other forms of monitoring to verify that they do not pose a security hazard or security;
  • The lack of port state regulations to ensure the safety and security of laid up vessels in UK ports and harbours.

Actions or events that reduced the adverse consequences of this maritime incident include:

  • That the anchors of VALARIS DS-4 and ENSCO DS-8 had been pre-deployed when the drillships were moored at Hunterston Jetty and that the anchor of VALARIS DS-4 was reset and kept the drillship amid of the channel after being blown off the pier after loss of mooring lines; and
  • The arrival of tugs to hold ENSCO DS-8 alongside the wharf.



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