Vessel’s breakaway due to wind causes damage at pier
The Australian Transport Safety Bureau issued an investigation report on an accident that happened at Station Pier, Melbourne, on January 2016, on a passenger ship, which was struck by strong winds while loading operations, causing severe damage to the shore infrastructure.
On the afternoon of 13 January 2016, the roll-on/roll-off passenger ship Spirit of Tasmania II was loading cargo, vehicles and passengers at Station Pier, Melbourne. At 1752, strong wind gusts blew the ship off the wharf and all but two of the ship’s mooring lines (on the bow) parted. After breaking away, the stern swung around until the ship was 90 degrees to the wharf, parallel to nearby Port Melbourne Beach and in danger of grounding. While waiting for tugs to assist, the ship’s propulsion and thrusters were used to maintain its position and prevent grounding. By 1905, the ship was back alongside the wharf, assisted by two tugs.
The ship suffered minor damage to its lower bow ramp and bow doors. Shore infrastructure suffered extensive damage to the elevated roadway and ramp arrangement on the wharf and minor damage to wharf structures. No one was injured.
Spirit of Tasmania II’s upper and lower bow ramps deployed at Station Pier
What the ATSB found
During the afternoon of 13 January, a band of severe thunderstorms passed across the location of Spirit of Tasmania II, with little warning. As the ship’s bridge was unattended throughout the port stay, none of its crew saw indicators of the approaching storm until just before the breakaway.
The ship’s crew responded swiftly. The bridge was manned and machinery was operational by the time the ship had turned 90 degrees to the wharf. The ship’s movement was then controlled using its thrusters and main propulsion until, with tug assistance, it was returned to the wharf.
Spirit of Tasmania II’s damaged upper bow ramp (skybridge)
- At 1753 on 13 January, the wind speed suddenly increased from about 25 to 60 knots during a thunderstorm resulting in a six-fold increase in the wind loading force acting on Spirit of Tasmania II.
- The exponential increase in the wind loading force pushed the ship’s stern off the wharf, stretching its aft mooring lines.
- Soon after 1753, the shortest of the three stern lines (all held on winch brakes) stretched beyond its limit and parted. As the load transferred to the remaining stern lines, they parted in quick succession.
- The two breast lines aft (held on self-tension winches) payed out before parting, allowing the stern to breakaway.
- While the weather experienced, in general, was forecast well in advance, the thunderstorm was not specifically predicted until 15 minutes before the breakaway leaving little time for the ship’s crew to respond.
- The adverse weather procedures for TT-Line Company ships when alongside did not take into account all the necessary factors to provide effective defences against significant, short-term weather events such as thunderstorms and squalls.
What’s been done as a result
The ship’s managers, TT-Line Company, advised the ATSB that it has implemented immediate changes to shipboard weather monitoring and notification arrangements along with changes to heavy weather and mooring procedures. These changes include: weather triggers for increased shipboard readiness; immediate notification of weather warnings; access to the Bureau of Meteorology (BoM) website from the bridge; changes to the wind speed alarm settings and; requiring all mooring lines to be held on the winch brakes.
TT-Line also engaged external marine consultants to complete extensive investigations and analyses into the mooring requirements and design for Station Pier. The consultants have completed mathematical modelling and incident replication simulations. Subsequent analyses will be used to identify and define operational parameters and recommend any alterations to berthing arrangements and infrastructure. The ATSB has issued one recommendation to TT-Line to complete safety action to adequately address the safety issue with respect to moorings.
CCTV images showing the ship moving off the wharf and the first line parting
The Victorian Ports Corporation (Melbourne) advised the ATSB that Melbourne vessel traffic service will broadcast BoM weather warnings on VHF channel 12. All masters of ships in port waters, including at berth or anchorage, are to ensure a listening watch is maintained at all times.
The BoM advised the ATSB that in addition to verifying the subscription service with the Victorian Ports Corporation (Melbourne) it continues to upgrade its marine weather services. This includes a one-stop webpage on its website for improved education, information and accessibility to marine and ocean services.
All ships, especially those with high windage, are prone to breaking away from moorings during short-term events, such as thunderstorms and squalls. The risks this presents to ships with large numbers of people on board mean that weather monitoring, mooring systems and procedures need to be regularly checked and verified for changing weather conditions.
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Source: Australian Transport Safety Bureau