November 25, 2017
The following Insight from Mike Priestly, Senior Consultant, provides incident commentary on the Spirit of Tasmania II parting of moorings:
Background
On 13 January 2016 The Spirit of Tasmania II broke from her moorings while loading vehicles and passengers at Station Pier Melbourne. The ATSB recently published a report of its investigation (link).
Purpose
ONA offers commentary on the incident and findings in light of its work as mooring specialists. ONA explores the background and challenges facing safe mooring operations and the use of robust marine risk assessments. ONA reviews the history of similar incidents and identifies an opportunity for better use of risk assessments to drive practicable, safe operational procedures.
The Incident
ATSB reported:
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.
Mooring Equipment
The report acknowledged Spirit of Tasmania II was fitted with mooring equipment commensurate with the size and type of ship as required by the classification society. This forms the bare minimum for mooring equipment regardless of the operational profile. ATSB reported that although the mooring lines parted, there were no other failures in mooring equipment.
Mooring up is also dependent on the capacity and arrangement quayside. Station pier was designed for Ro-Ro operations. Following this incident, consultants were engaged to assess the adequacy of Station Pier infrastructure.
Although The Spirit of Tasmania II mooring equipment and quayside infrastructure appeared adequate for the operations, similar ship excursions occurred in October 2002 and August 2009 with similar outcomes. Mooring procedures in the context of adverse weather were the focus of investigations into those incidents.
Incident Cause
The 2016 incident was caused by un-anticipated high wind loads parting the mooring lines and an uncontrolled excursion of the stern of the ship from the pier. The Master and crew acted swiftly to stop loading, arrest the ship and stabilise the situation.
Amongst other contributing factors, the ATSB reported:
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. [Safety issue]
TT Line reported to ATSB remedial action taken included updating and expanding procedures in relation to weather preparations and responses at Station Pier as well as engaging external consultants to review mooring conditions and arrangements.
Initial Response
Although the forecast was for thunderstorms that afternoon, the Master did not know about a severe thunderstorm warning issued shortly before the incident. Therefore, the Master did not have the opportunity to prepare for contingencies. He was forced to respond to the unfolding incident.
If afforded the opportunity to prepare, what steps might he had taken either pursuant to the ship board procedures in combination with his professional skill and judgement?
He might have stopped loading immediately. He might have altered the mooring arrangements but how? If moored in accordance with adverse weather procedures, he might have had limited further options available. He might have called for engine power and got the stern thruster on line immediately. But would 15Te of thrust been enough? He might have requested local harbour tugs to mobilise to push up and hold the ship. How long would mobilisation have taken for any meaningful and effective response?
The ATSB report did not detail the adverse weather (while alongside) procedures but it did recommend such procedures be reviewed.
That review should involve the application of an operational risk assessment methodology and framework.
Operational Risk Assessments
At ONA we routinely use analysis including assessment of design loads, tension sensitivity studies and sequential failure analysis. Simulations forms part of this work and is very important in the correct context. While these forms of analysis are highly beneficial for understanding infrastructure capacity and utilisation limitations, the use of simulation should be tempered with some hard-operational thinking within risk assessment framework.
All stakeholders should be encouraged to participate in assessment process (for the sake ownership, training and collective wisdom) including persons responsible for developing, documenting, implementing and revising the new operational procedures. They need to drive the analysis and simulation work and not the other way around, otherwise the risk is an outcome that is costly and academically fulfilling without tangible benefits.
When these analytical tools are used as part of a formal risk assessment process, important operational and commercial decisions can be justified. While this may appear to be detrimental to OPEX considerations it generally leads to safer and more defendable outcomes.
