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Accidents

Nautilus III / H7 (2001)

Nautilus III girted, capsized, and sank after hopper barge H7 sheered across Auckland Harbour, with both people involved escaping without injury.

Classification

  • Incident Type: Capsize girding
  • Severity: High
  • Primary Source: TAIC Report 01-204

Vessel Details

FieldValue
Vessel NameNautilus III / H7
Vessel NamesNautilus III / H7
Vessel TypeTug
Flag State
IMO Number
Gross Tonnage30
LOA (m)14.16
Breadth (m)5.27
Bollard Pull (t)9
Power (kW)336
Owner/OperatorThomson Towboats Limited
Year Built1971
Crew Size1 on Nautilus III; 1 on H7

H7 was a 47.64 m, 190-gross-tonnage hopper barge owned by Ports of Auckland Limited and loaded with harbour dredgings.

Incident Details

FieldValue
Date2001-03-09
LocationAuckland Harbour, near Fergusson Container Terminal
RegionOther
Coordinates-36.8521, 174.7632
Fatalities0
Injuries0
Missing0
Investigation BodyTAIC
Direct DamageMinor superstructure and hull damage with extensive water damage
Economic Damage

Key facts

  • Nautilus III was towing the loaded hopper barge H7 from Marsden Wharf to a mixing barge in Mechanics Bay.
  • A 20 m towline with a fixed eye at each end left the crew unable to slacken or release it as H7 yawed and then sheered to starboard.
  • The towline led close to abeam, girting the tug and heeling it until flooding began through an open watertight door.
  • The tug's skipper swam to H7, the barge deckhand was uninjured, and another tug recovered the barge.
  • Nautilus III sank, caused minor diesel pollution, and was raised and refloated later that day.

Narrative

At about 0705 on 9 March 2001, Nautilus III departed Marsden Wharf to tow the loaded hopper barge H7 approximately one nautical mile to a mixing barge in Mechanics Bay. H7 carried harbour dredgings and was trimmed by the head. The tug's skipper and a deckhand used a 20 m polypropylene towline with an eye fixed over the tug's H post and the other eye over a bollard on H7. The deckhand remained aboard the barge, leaving the skipper alone on the tug.

As the tow proceeded through Auckland Harbour, H7 yawed by as much as 40 degrees either side of the intended track. Near Fergusson Container Terminal at about 0720, the barge sheered about 60 degrees to starboard and began to overtake the tug. The skipper applied power and altered course in an effort to arrest the sheer, but the towline shifted toward the tug's starboard beam. Nautilus III heeled and became girted.

The heel increased until the sill of an open watertight accommodation door submerged and downflooding began. The skipper attempted to turn the tug further to port, but water was already entering the starboard engine-room ventilator. The deckhand on H7 could not find a tool to cut the partly chafed towline. Within about 15 seconds of the skipper recognizing the girding condition, Nautilus III rolled onto its starboard side and sank. The skipper swam clear along the towline and climbed onto H7. Another harbour tug recovered the barge.

Minor diesel pollution escaped from the wreck, but divers sealed the tanks by 1005. Because the sunken tug obstructed navigation, salvage began immediately. A floating crane raised Nautilus III at about 1500, after which it was pumped out and refloated. The tug sustained minor hull and superstructure damage and extensive water damage.

TAIC found that the short towline, H7's bow-down trim, the method used to control yaw, and differing tidal currents contributed to the barge's uncontrolled sheer. Fixed towline eyes prevented emergency release, while the open watertight door accelerated downflooding. The Commission concluded that deficient planning, communication, and towing precautions made the short harbour operation vulnerable to foreseeable risks.

Sequence of events

Date/timeEvent
2001-03-09 07:00 localThe skipper and deckhand prepared Nautilus III for the day's work.
2001-03-09 07:05 localThe tug departed Marsden Wharf to collect H7.
2001-03-09 07:10 localThe tow left the wharf with the deckhand remaining aboard H7.
2001-03-09 07:20 localH7 sheered to starboard near Fergusson Container Terminal and began overtaking the tug.
2001-03-09 07:25 localNautilus III became girted, flooded through an open watertight door, capsized, and sank.
2001-03-09 10:05 localDivers had sealed the tug's fuel tanks after minor diesel pollution.
2001-03-09 15:00 localA floating crane raised Nautilus III for pumping out and refloating.

Contributing factors

FactorEvidence statusDescription
Poor tow geometryConfirmed findingH7 was trimmed by the head and the 20 m towline was too short, causing excessive yaw.
Uncontrolled barge sheerConfirmed findingTAIC attributed the sheer to a combination of poor tow geometry, the yaw-control technique, and differing tidal currents.
No effective towline releaseConfirmed findingFixed eyes at both ends prevented the crew from slackening, releasing, or severing the towline during the emergency.
Open watertight doorConfirmed findingThe open accommodation door reduced the heel angle at which downflooding began and increased the flooding rate.
Planning and communicationConfirmed findingThe operation was not discussed in depth, and the skipper did not know that the deckhand would remain aboard H7.

Investigation

The Transport Accident Investigation Commission investigated the casualty and published Report 01-204, Tug Nautilus III capsize and sinking. TAIC found that H7's trim and the short towline produced poor tow geometry; the barge's uncontrolled sheer girted the tug; the fixed towline arrangement limited emergency options; and an open watertight door allowed excessive downflooding. The Commission issued safety recommendations on towing procedures, watertight integrity, emergency arrangements, crew communication, and the provision of a way to sever towlines aboard the barges.

References

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