The UK Marine Accident Investigation Branch (MAIB) has released its investigation report into the August 2016 grounding of semi-submersible drilling rig Transocean Winner on the Isle of Lewis following the loss of tow.
The Marshall Islands registered rig grounded on the morning of August 8, 2016 on the north coast of the Isle of Lewis, Scotland following the loss of tow from the Dutch registered tug ALP Forward. The tug and tow was on passage from Stavanger, Norway to Valletta, Malta, where the 30-year-old rig was due to be de-commissioned or sold for scrap, when it encountered severe weather west of the Hebrides, located to the west of mainland Scotland.
The MAIB report said the effect of the wind and waves on Transocean Winner led to the loss of ALP Forward’s ability to control the direction and speed of the tug and tow. After being dragged backward by the tow for over 24 hours, the tow line parted and the tug was unable to pick up the emergency towline. The MAIB reported noted that the tow line was already in a deteriorated condition before the tow commenced, and it was further weakened during the heavy weather prior to the accident.
The Transocean Winner was refloated on August 22 and was eventually loaded onto a heavy lift vessel and transported the rest of the way to Malta.
Safety issues identified in the report are as follows:
- The effect of the wind on Transocean Winner led to ALP Forward being incapable of controlling the wind and tow in the severe weather conditions. Without the necessary information, it was not possible for the master to predict the tug’s inability to hold the rig and change his passage plan in time to seek shelter.
- The planning of a passage so close to the coast left little sea room for the tug and tow to drift. When ALP Forward lost control of the tug and tow, it was very likely that Transocean Winner would have grounded even if the tow line had not parted.
- The tow line was in a generally poor condition, there was insufficient catenary in the deployed tow line which led, in the weather conditions, to repeated sudden loadings resulting in the tow line parting. It is quite possible that a new tow line would have also parted under the same circumstances and conditions.
The MAIB report recommended that ALP Maritime Services, as manager of the ALP Forward, review its procedures with regard to the production of towing manuals to ensure that the guidance provided in them:
- Complies with the guidelines issued by the International Maritime Organization in MSC/Circ.884 of 1998
- Provides those responsible for the safety of the tow with all the necessary information, including tow-specific guidance on:
- The need to consider sea room and lee shores during passage planning
- The provision of an adequate catenary
- The need to report when control of the tow is lost
- The limitations/ functionality of the emergency towing arrangement when in adverse weather
- Provides its vessels’ crews and maintenance staff with comprehensive guidance on the maintenance, inspection and discard of tow lines
Transocean has also started its own internal investigation into the accident.
You can find the MAIB’s full Accident Investigation Report HERE.