Oil rig salvage: what have we learnt from Lewis?
In August the TransOcean semi-submersible oil rig Winner became grounded on the Isle of Lewis in the Western Isles of Scotland. Given the significant environmental risks associated with oil spills, this incident has naturally caused concern. So how exactly did it happen, and how can similar groundings be prevented in the future? Molly Lempriere investigates.
The TransOcean Winner was under tow from Norway to Malta with the eventual destination of Turkey when severe weather snapped the tow line on the evening of 7 August. Left adrift, the rig became grounded in Dalmore Bay on the west coast of the Isle of Lewis.
The Winner was initially moved to undergo “decommissioning and scrapping”, explains Hugh Shaw, the Secretary of State’s Representative (SOSREP) for Maritime Salvage & Intervention, a division of the Marine and Coastguard Agency (MCA). This process is far from unusual, with a large number of rigs being towed around the world. This was just one of a number of TransOcean rigs alone that use this method of transportation and these waters, Shaw explains. But it is unusual for one, such as the 17,000-tonne Winner, to go astray, raising many issues around the safety of this process.
Fixing the rig
On 8 August a perimeter was set up by local emergency services, and the Marine and Coastguard Agency and the Marine Accident Investigation Branch (MAIB) were at the site by the second day. Together they helped form a multi-agency response that sought to refloat the rig as quickly as possible. However, damage to the rig complicated the responders’ efforts.
“We knew then that [the rig] was badly damaged so that any opportunities to do a conventional tow, as had been happening before the accident, were fairly limited to non-existent,” says Shaw.
Thus the 93m long Winner was subject to basic repairs, including the removal of the remaining oil from the rig, before being tugged out to Broad Bay further off the coast. Here the rig was loaded onto a semi-submersible heavy lift ship, the Hawk, which set out for Malta on 14 October.
The refloatation of the rig was repeatedly hampered by poor weather, but regardless Shaw is proud of how fast it was achieved. “It took a little over two months to do and I think it's been quite an achievement to have a rig that grounded to manage to successfully refloat it, to get it around to Broad Bay to get it loaded onto a heavy lift ship, all within about nine weeks,” he said.
Following the Winner’s departure, work began to ensure the area has been not permanently damaged. “We've been doing sampling and ROV service of the sea bed just to ensure there is no debris or anything left on that site,” Shaw says. Although current environmental reports seem positive, TransOcean has also made a £120,000 donation to Dalmore and Caloway, the nearest communities, to apologise for the disruption caused in the past months.
Has the rig left its mark?
There has been mercifully little damage done to the environment, despite the rig carrying 280 tonnes of diesel on board, stored within four tanks, two of which were damaged. “Our concern was that we still had fuel in some of the undamaged tanks on the rig when it was aground, so it was a top priority to get that safely away from the lower part of the rig into tanks in a higher position,” says Shaw. This was a particular worry as “we were very conscious that within about four miles of the grounding site there was up to 27 aquaculture sites so we planned about the industry there,” he adds.
The two damaged tanks led to the loss of 53,000 litres of oil, but Shaw is keen to emphasise that this has not caused a great deal of damage. “We brought the surveillance aircraft in quickly, and by that time it wasn't detecting anything,” he says. “I think there was a very light sheen in the area which dispersed extremely quickly on that side.”
This sheen went alongside a strong smell of oil on the first morning, which quickly passed. Marine Accident Investigation Branch (MAIB) chief inspector of marine accidents Captain Steve Clinch reaffirms Shaw’s assertion, highlighting that “marine gas oil is quickly broken down and dispersed so it is possible that no lasting pollution was caused by this incident”.
Following the loss of the fuel there has been extensive testing to ensure that the water is unpolluted. Shaw’s team “looked back at any base line statistics they did have [for Dalmore], and then they carried out extensive sampling of water and air quality and that didn't give us any concern”. The testing was extensive, Shaw says, including “looking at fish, taking samples of fish and right down to taste-testing at our lab in Aberdeen”.
Hydrocarbon pollution is not the only environmental worry, however, as the debris caused by the collision was also scattered across the surrounding area. “I was concerned that if any debris had come off the rig itself, that is, any pieces of metal or whatever, that we didn't want to reopen the beach until we were satisfied it was safe for people to go in the water again,” Shaw says. Dalmore is a very popular beach on the island, particularly for surfers. Already more than 15,000 tonnes of debris has been collected from the site, but there is likely to be more.
TransOcean has already set up a scheme working alongside the MCA to clear the beach of debris for a minimum of twelve months. They will work in cooperation with local people, who can report any potential items related to the grounding, which will then be cleared by TransOcean. Shaw says this “will continue until I'm happy and the environment group [is] happy that there is nothing further left on the sea bed”. The amount of debris found is likely to increase over the winter months as “storms may uncover some debris which may have worked itself down into the sand at the moment which hasn't been detectable by the surveys,” he explains
Have lessons been learnt?
By and large, the rig has caused little damage to the island, and has already made it to Malta for deconstruction. At present the MAIB is conducting an investigation into the incident.
“The causes and circumstances of the grounding, together with any recommendations on how to prevent an accident like this happening in the future will be established during the current MAIB investigation,” confirms Clinch.
But certain aspects of the incident have already come under scrutiny, not least the availability of emergency tug vessels (ETVs). Scotland previously had two ETVs; however following a controversial decision in 2012 this was cut back to just one. Thus when the Winner was grounded, the nearest emergency vessel was over 14 hours away. Shaw suggests this may not have actually made a difference to the response to the incident, though.
“The rig itself was unmanned so in the weather conditions they had, it was always going to be extremely difficult to do a reconnection. So I suppose even if there had been another emergency tug there, once the line had parted it would have been quite dangerous and extremely difficult to make that reconnection”.
Criticism has also arisen from those who feel that decommissioning work could be carried out in Scotland, especially following the Winner’s grounding. Shaw explains that “there is a feeling that when it ran aground the question was asked politically, were there any facilities closer than trying to tow or put on a heavy lift ship all the way back out to Malta and then on to Turkey?” But both Shaw and Clinch emphasise that it was “a commercial decision taken by the owners of the rig”, and apart from minor repairs undertaken in Broad Bay the work will be done in Malta.
The MAIB report will ultimately prove how successful the response to the incident has been, although it was dealt with quickly and with impressively little environmental damage. Despite this Shaw assures that “there will always be lessons learnt, so we will have a debrief to see what else comes out; could we have done things differently? But I think the satisfying thing from my side is that apart from the initial small quantity of oil that was lost we managed to avert any further damage.”
Clinch says that “the MAIB investigation will also consider whether similar incidents could be handled better in the future”. But until it is published, many are just thankful the rig is back on its way.