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Accidents

Thorngarth / Stolt Aspiration (2005)

The tug Thorngarth crossed the bow of Stolt Aspiration during a bow-to-bow towing connection on the River Mersey and was struck on its starboard side.

Classification

  • Incident Type: Collision
  • Severity: Medium

Vessel Details

FieldValue
Vessel NameThorngarth
Vessel NamesThorngarth / Stolt Aspiration
Vessel TypeTug
Flag StateUnited Kingdom [GB]
IMO Number8311998
Gross Tonnage365
LOA (m)36.28
Bollard Pull (t)45
Year Built1983
Crew Size4

Incident Details

FieldValue
Date2005-04-13
LocationApproaches to Alfred Lock, Birkenhead, River Mersey
RegionUnited Kingdom
Coordinates53.3933, -2.9166
Fatalities0
Injuries1
Missing0
Investigation BodyMarine Accident Investigation Branch (MAIB)
Direct DamageThorngarth was holed below the waterline and sustained significant structural damage; Stolt Aspiration sustained minor bow damage.

Key facts

  • At about 02:10 local time, Thorngarth was attempting to connect as bow tug while Stolt Aspiration approached Alfred Lock.
  • Thorngarth moved across the tanker's closing bow while trying to recover position, and Stolt Aspiration struck the tug's starboard side.
  • Thorngarth was holed above and below the waterline, and its engineer sustained a broken arm; the report recorded no other injuries or pollution.
  • Stolt Aspiration sustained a small dent to its bulbous bow and continued into Birkenhead Docks with the after tug.
  • The MAIB attributed the collision to the tug master's unfamiliarity with Thorngarth and insufficient training for the bow-to-bow manoeuvre.

Narrative

Shortly after 01:00 on 13 April 2005, Stolt Aspiration left QEII Lock at Eastham for East Lewis Quay, Birkenhead. The Liberian-registered chemical/oil carrier was 128.91 m long, measured 7,901 GT and carried 23 people. A pilot was aboard for the River Mersey passage and the approach to Alfred Lock. Thorngarth and Ashgarth were assigned to assist, with Thorngarth acting as bow tug and Ashgarth assisting aft.

Thorngarth was a 45-tonne bollard-pull twin azimuthing stern drive tug designed to pass its towline from the bow. Connecting required the tug to approach Stolt Aspiration bow-to-bow, pass the line, then reverse stern-first into towing position. As the tanker approached Alfred Lock at about 6.5 knots and slowing, Thorngarth moved under its bow and received a heaving line. The tug then backed away, but its stern moved to port. The master corrected the swing and increased power to regain position ahead.

When the stern again moved to port, a further correction carried Thorngarth toward the tanker's starboard bow. The master then tried to recover the tug's position directly ahead, but Thorngarth moved across the path of Stolt Aspiration's bulbous bow. The tanker struck the tug's starboard side at about 02:10, heeling and displacing Thorngarth to port. Stolt Aspiration's pilot immediately ordered full astern, used the bow thruster to maintain heading and directed Ashgarth to pull astern at full power. The MAIB found that these actions limited the impact but that the tanker crew had no practical opportunity to prevent the collision.

Thorngarth's engineer suffered a broken arm. The impact opened the tug's starboard side above and below the waterline, buckled shell plating and internal structure, and damaged the starboard main-engine cooling system. After pulling clear, Thorngarth crossed to Princes Landing Stage, where the engineer was transferred to an ambulance and crews from two other tugs reduced the flooding. The damaged tug was beached at Kings Dock River Wall at about 03:10, dried out with the tide, temporarily repaired and refloated at 13:30. Stolt Aspiration sustained only a small dent to its bulbous bow and completed the berthing operation. The report recorded no other injuries or pollution.

The MAIB found no mechanical failure or fatigue-related cause. It concluded that Thorngarth's master was unfamiliar with the tug's manoeuvring response, misjudged the control movement needed and had not been adequately trained for the manoeuvre. The investigation also identified weaknesses in familiarisation, experience recording and tug-to-task allocation.

Sequence of events

Date/timeEvent
2005-04-13 01:00 localStolt Aspiration left QEII Lock for East Lewis Quay, Birkenhead.
2005-04-13 01:47 localThe pilot contacted the assisting tugs and agreed the working VHF channel.
2005-04-13 02:10 localStolt Aspiration struck Thorngarth as the tug crossed the tanker's bow while recovering position.
2005-04-13 03:10 localThorngarth was beached at Kings Dock River Wall to control flooding and dry out.
2005-04-13 05:35 localThorngarth dried out as the tide fell.
2005-04-13 13:30 localThe tug refloated after temporary hull repairs.

Contributing factors

FactorEvidence statusDescription
Tug-master familiarisationConfirmed findingThe master was unfamiliar with Thorngarth's manoeuvring characteristics and misjudged the control movement needed to recover position.
Manoeuvre-specific trainingConfirmed findingThe master had observed the bow-to-bow manoeuvre but had not previously conducted it in command of Thorngarth.
Control response during recoveryConfirmed findingCorrecting the tug's swing reduced astern motion and carried Thorngarth toward the tanker's bow before the final recovery attempt crossed its path.
Experience recordingConfirmed findingThe previous training system relied on experience accumulated over time but did not maintain records showing which manoeuvres personnel had completed.
Tug-to-task allocationConfirmed findingThe allocation system ensured the required bollard pull but did not necessarily select the optimum tug type or verify the experience needed for the task.

Investigation

The Marine Accident Investigation Branch published report 21/2005 in November 2005. It concluded that the collision was caused by the tug master's unfamiliarity with Thorngarth and lack of training in the required bow-to-bow manoeuvre. The MAIB recommended closer monitoring of personnel movements between tug types, matching training and expertise to the assigned tug and task, and regular formal discussion among port authorities, pilots and tug operators about tug allocation and crew experience.

References

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