West Gamma

Rig:

West Gamma Jack-up

Date:

20 August 1990

Location:

German Bight, North Sea

Activity:

Rig move

Summary

On 20 August 1990, the West Gamma accommodation jack-up ran into a gale (with waves up 12 meters and winds gusting 60 knots) as it was being towed by the Normand Drott from the Norwegian sector to the German sector. The rig first lost its helideck to a large wave, then lost its tow with the Normand Drott during the storm, causing the rig to drift towards the German coast.

As night fell, one of the deck lifeboats broke loose, damaging vent pipes and access hatches and causing down-flooding in the rig's hull. By 0100 hours, the rig had assumed a 10 degree list. By 0200 on 21 August, conditions deteriorated to the point where it became necessary to evacuate the crew. Evacuation by helicopter was not possible due to the damage sustained to the helideck and helicopter winching was not possible due to the high winds. The excessive movement as the rig pitched and rolled in the heavy seas also made it all but impossible to launch the lifeboats. Fortunately for the rig's crew, two Danish ESVAGT standby/rescue vessels (the Omega and the Protector) were despatched from the Danish sector to aid the evacuation. Members of the rig's crew tied themselves together in groups of 5 or 6 and jumped into the sea from the first level of the accommodation as a rescue helicopter's searchlight illuminated the scene. Four fast rescue craft belonging to the ESVAGT vessels formed a horseshoe downwind of the rig then picked up the crew.

At 0307 hours on 21 August 1990, the rig sank off the coast of Helgoland, Germany, in 44m of water, with the highest point of the rig only 10m below sea level at low tide. As German authorities decided in 1993 to use this area as an emergency anchorage area, the underwater obstruction created by the West Gamma had first to be cleared. In 1994, the rig was demolished in stages. The legs were first cut then blown free of the rig with explosives. Using an underwater hydraulic jackhammer, the West Gamma's hull was then crushed until the highest point was 25m below low tide sea level.

Bad weather, loss of the towline, structural failure and flooding all contributed to the eventual sinking of the West Gamma. The captain of the Normand Drott said after the event that the risk to the rig crew would have been lessened if "the UK practice of using two tugs and an auxiliary vessel had been used".

Sources:

ESVAGT
Jan Erik Vinnem: Offshore Risk Assessment (1999)
Ships And Oil (MMASS)
Crawford & Company (Nederland) BV: Personal correspondence

Photos
1. Fluemer Aerophoto
2, 3 & 4. ESVAGT