Friday, July 14, 2000

U.K. publishes report on "killer wave" accident

Britain's Marine Accident Investigation Branch (MAIB) has now published its official report into the man overboard fatality from the angling boat Purdy, at Shipwash Bank, off Harwich, on July 17, 1999.

This was the incident that gave rise to headlines about high speed ferries generating "killer waves," after the Purdy reported that it had been swamped by a very large wave, with one person lost overboard.

According to the MAIB, Purdy, a 10 m long, Aquabelle angling boat with the skipper and one guest on board, was preparing to anchor and begin fishing on a shallow sandbank off the East Anglian coast when the Stena Discovery high-speed ferry passed inbound for the port of Harwich. Purdy's skipper turned his boat towards the wash from the high-speed ferry.

The weather was fine with good visibility and a slight sea. As the first wash waves approached Purdy they appeared to grow in height to 4 m and begin to break. The first wave crashed over Purdy's bow swamping the vessel and washing the guest, a John Sibley who had been sitting on the engine casing aft, overboard.

The skipper threw a lifebuoy towards the man in the water and tried to maneuver the boat towards him. The man disappeared from view.

Despite extensive searches carried out by the skipper and the rescue services, his body was not recovered until 12 days after the accident. He had been wearing heavy leather boots and no lifejacket.

An interim recommendation was addressed to both the U.K. Maritime and Coastguard Agency (MCA) and Stena Line BV to carry out route assessment trials with respect to wash generation.

The MAIB is now making further recommendations to the MCA to ensure that all operators of high-speed craft undertake route assessment trials with respect to wash generation as a requirement for issuance of a Permit to Operate. Guidance criteria should be developed on maximum permitted generated wave heights for measuring the efficacy of the route assessment results.

The MAIB's findings are

  • The victim was washed over the side from Purdy at about 0936 on 17 July 1999 by a large wave.
  • The victim was not wearing a lifejacket.
  • Purdy was well equipped and maintained.
  • Purdy's skipper was very experienced, although unqualified.
  • At the time of the accident, there was a southerly wind of force 3, good visibility and a slight sea and swell.
  • It is likely that Purdy had less than 3 m of water beneath her keel and possibly less than 2 m.
  • Stena Discovery had passed just over a mile from Purdy about 3 minutes before the wave struck.
  • Stena Discovery had been operating on the Hoek van Holland/Harwich route since June 1997.
  • High-speed craft, like Stena Discovery, were known to have the capability to produce waves that can be accentuated and become dangerously high in shallow water.
  • Stena Discovery had a valid Permit to Operate, which covered the port of Harwich.
  • Stena Discovery's route and speeds on approach to Harwich had been revised several times in response to information about incidents on the beaches and some off-lying banks.
  • The changes to Stena Discovery's approach had been largely successful in reducing the impact of waves on the beaches to within acceptable limits.
  • On July 17, 1999, Stena Discovery was operating on a route and at speeds in accordance with the current guidance.
  • Very little feedback had been received, before the accident, about the danger of wash waves on off-lying banks. However, attempts had been made to give appropriate warnings.
  • Purdy's skipper was not aware of warnings concerning the danger of Stena Discovery's wash on off-lying sandbanks.



The accident occurred when a wash wave, generated by HSS Stena Discovery and having grown to about 4 m in height as it encountered the shallow waters on the southern end of the Shipwash Bank, broke over and swamped the angling boat Purdy.


  • The wave was generated by Stena Discovery during or after the alteration of course made to the south of South Shipwash buoy. Its height and steepness were probably accentuated by focusing due to the particular bathymetry and superposition with wash waves generated before the turn.
  • The skipper of Purdy had not been aware of the broadcasted dangers associated with shallow banks and the passage of Stena Discovery.
  • The skipper had placed Purdy in a dangerous position with regard to the wash waves that Stena Discovery was known to produce.
  • The victim was not wearing a lifejacket. Had he done so, his chances of survival would have increased.
  • The skipper could have done more to ensure the safety of his boat and her occupants.
  • Wash generation by HSS 1500s is complex and is not yet fully understood.
  • It is likely that Stena Line BV was aware that wash would impact on Shipwash Bank and that the Bank would, to some extent, protect the bathing beaches at Dovercourt and Felixstowe. However, it did not expect waves of 4 m height to be produced.
  • There was a shortfall in safety management by Stena Line BV in that no documented risk assessment of the route with regard to wash generation was carried out prior to Stena Discovery commencing operations, despite prior knowledge of the problems being experienced on Irish Sea routes.


During the course of the investigation, in August 1999, the following safety recommendations were issued:

The Maritime and Coastguard Agency was recommended, as an interim solution, (1) to insist, through the Netherlands Shipping Inspectorate, that Stena Line Holland BV: instruct masters of the HSS ferry to change their passage plan and reduce speed to ensure safe entry to Harwich Haven including the reduction of wash on adjacent sandbanks; (2) begin monitoring the wash in the approaches to Harwich Haven, to ensure the action taken reduces it to within safe limits.

Additionally, the MCA was recommended to (3) instigate through the Thames Coastguard, a marine safety broadcast on VHF radio to warn small boat users of the dangers associated with the wash of the HSS.

Towards a permanent solution, MCA, was recommended to (1) insist, through the Netherlands Shipping Inspectorate, that Stena Line Holland BV carry out a full risk assessment of the approach to Harwich Haven with reference to wash and, as a result, propose a route and speed profile that constitutes a permanent solution; and (2) liaise with the Netherlands Shipping Inspectorate to ensure that the Permit to Operate and Route Operations Manual are endorsed with the requirement for a full risk assessment with reference to wash, and for all likely areas of wash to be identified, and action taken to avoid it.

In recommendations to small boat users, the MAIB reminded all users of small craft of the dangers that can arise unexpectedly from the wash of passing vessels. In deciding whether to wear lifejackets, it should be remembered that no harm comes from wearing them in even the most benign conditions, and that they may save lives if an unexpected event occurs.

Other recommendations made at the completion of the investigation:

The Maritime and Coastguard Agency is recommended to:

  • consider instigating procedures whereby a full route assessment with respect to wash is undertaken by all operators of high-speed craft who apply for a Permit to Operate;
  • consider establishing maximum wave height criteria for measuring the efficacy of the route assessment results;
  • consider the implementation of international regulations in this respect by raising the subject at the International Maritime Organization when the High-Speed Craft Code is next reviewed.

The Hydrographic Office is recommended to:

  • Review the content of Admiralty Notices to Mariners Number 23, to give appropriate warning concerning the risks of large waves on shallow off-lying banks.


U.K. Maritime and Coastguard Agency response
In a statement today, the MCA notes that the recommendation that operators of high-speed craft who apply for a permit to operate undertake a full route assessment with respect to wash is now a condition of the Permit to Operate, which is issued to all operators of High-Speed Craft operating in U.K. ports.

The MCA says it is considering the recommendation that it establish maximum wave height criteria for measuring the efficacy of the route assessment results.However, the MCA believes that the risk assessment approach allows for flexibility in terms of the differing requirements of an area and along specific areas of a route.

On the recommendation that it raise the subject of appropriate international regulations at IMO, the MCA notes that it is proposing to submit a paper to IMO later this year. This paper will draw on a research project commissioned by the MCA and aims to inform the next review of IMO's High Speed Craft Code.

Cammell Laird to refurbish sub for Canada
Britain's Cammell Laird has won a contract from BAe Systems to support the maintenance of former Royal Navy submarine, HMS Unseen, for the Royal Canadian Navy.

HMS Unseen is an SSK Upholder (Type 2400) diesel-powered conventional submarine built at Birkenhead for the Royal Navy. It is one of four conventional submarines that are to be transferred from the Royal Navy to the Royal Canadian Navy over the next few years, All four have been mothballed since the mid-nineties following the U.K.'s decision to pursue an all-nuclear submarine policy.

BAe Systems, Barrow-in-Furness, was awarded the contract from both the Royal Navy and Royal Canadian Navy to reactivate, refurbish and modernize all four submarines prior transfer to Canada. The transfer involves a lease/purchase deal between the UK and Canadian Governments.

The HMS Unseen was launched in 1989 and is one of the many submarines originally built at Cammell Laird's Birkenhead shipyard in the 1980's and has returned to her birthplace for drydocking prior to transfer to the Royal Canadian Navy.

The submarine arrived in Cammell Laird's Merseyside yard on July 4th and is expected to stay in dry dock for some 40 days prior to transferring to the yard's wet basin for a further 15-20 days. During the drydocking period, work will include renewal of the tailshaft bearings as well as a few other repair and refurbishment items required while the vessel is out of the water. It will then undergo trials and crew training at the yard's wet basin prior to sea trials.




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