INVESTIGATORS ARE examining how failure of a simple ballast tank valve on a state of the art berthing structure led to hundreds of passengers and their vehicles being stranded for 16 hours on an ultra-modern Stena ferry at Harwich Port in Essex last week.
It has also emerged that the port had no contingency plan for disembarking passengers - apart from taking the ship to another port - despite specific recommendations made a year ago by the Health & Safety Executive.
The incident has renewed calls by maritime design experts, in the wake of the Ramsgate walkway tragedy, for a specific code or guidance on the design, operation and maintenance of these structures (NCE 9 April).
The 650t floating vehicle ramp and passenger walkway doubles as a bespoke rigid docking and mooring system for the high-speed ferry. Only six of the ramps exist in the UK - one of which collapsed during installation at Holyhead in 1995 (NCE 12 October 1995). The ferry's innovative design makes it impossible to dock and unload at traditional berths.
The incident at Harwich occurred on the evening of 23 August. The port alerted the ferry only one hour before it was due to arrive at Harwich after noticing during routine checks that the berthing structure was floating around 1m too low in the water. Divers were brought in to investigate but were hampered by the ferry manoeuvring in the harbour.
The defective valve - normally only used to vary the buoyancy when the structure is installed - was eventually repaired and the ramp refloated. Mouchel, project manager for the structure's installation, then confirmed it was structurally safe. Vehicles finally left the ferry at 8:30am on Monday.
Investigations by Posford Duvivier into the incident are focusing on the design of the valve and the port's maintenance procedures.
Harwich Port project manager Bill Moger said that the HSE had issued an interim briefing note when the structure was first installed in June 1997. This highlighted particular items of the operation and maintenance procedure the HSE wished Harwich to concentrate on.
'They specifically wanted some alternative arrangement for getting passengers and vehicles off the vessel in the event of a failure,' Moger said. But although a temporary footway enabled passengers to leave the ferry during Sunday night, cars and lorries were stuck. Sending the ferry back to Hook of Holland, he said, was the contingency plan.
Moger added that he was expecting a report on the incident next week and would update the HSE on its findings. 'We need to find how we can improve matters - it really does need a proper code of practice.'
Past president of the Institution of Civil Engineers David Green, who is leading the battle for government funding to prepare a British Standard maritime code for ship to shore structures, said the incident was 'another example of the need for guidance'.
'The design and operation of these structures is very much a public safety issue. It should not be left to industry to fund research - Government should take the lead,' said Green. 'We put up a new submission to the DETR a couple of months ago with a more detailed proposal.Nothing has happened yet'.