A JACK-UP barge which ran aground off Orkney on an uncharted bank only 7.1 metres deep was being guided by a chart more than 160 years old, an investigation has revealed.
The Octopus barge had its legs extended to a depth of 13 metres, but the Admiralty chart for the area indicated a depth of greater than 20 metres with the closest sounding indicating a depth of 26 metres.
The report by the Marine Accident Investigation Branch (MAIB) says the source data diagram on the chart indicated the area was last surveyed, by leadline, in the 1840s.
The Octopus was being towed from Kirkwall to Seal Skerry Bay in the Orkney Islands by the tug Harald to act as a platform for the installation of a prototype tidal turbine when the incident happened on September 8 last year.
The tug and barge altered their route to pass to the west of Little Green Holm Island because of strong tidal streams experienced during the passage. This was a route not usually used by deep draught vessels and four of the barge's legs were damaged, resulting in substantial costs and project delays.
No-one was injured and the tug was undamaged.
The MAIB recommended the Department for Transport and the Maritime and Coastguard Agency should review the future work schedule for the UK Civil Hydrography survey programme in the light of the increasing use by large cruise vessels of sea areas not surveyed to modern standards.
They also recommended the UK Hydrographic Office put forward a proposal to international organisations that working groups investigated ways of ensuring electronic chart and display information systems provided a clear indication to mariners when the survey data used to produce the electronic chart was of poor quality.
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