Rig's grounding on Lewis 'could not be prevented'
The Transocean Winner could not have been prevented from running aground, MPs have been told.
Westminster's transport committee has been taking evidence of the grounding of the rig on Lewis in a storm.
Leo Leusink, of towing firm ALP Maritime Services BV, said the rig was too close to shore to stop.
Sir Alan Massey, of the Maritime and Coastguard Agency, also told MPs that weather conditions at the time were "phenomenal".
He said it was "very unusual" for the Western Isles to have such a sustained period of bad weather at that time of year and said the Transocean Winner was an "extreme example of a maritime casualty".
Sir Alan also said that an emergency towing vessel (ETV) would have unlikely to have been able to make a difference in such conditions.
He said the role of an Orkney-based ETV that did respond to the incident was still under investigation.
Until 2012, Scotland had two ETVs available for towing ships that had grounded or broken down on Scotland's north and west coasts.
One ship continues to operate out of the Northern Isles, but there have been calls from Scottish politicians and island local authorities for a second vessel to be reinstated.
Members of the committee sought evidence from its invited witnesses for information on what a Coastguard ETV may have made to the situation.
MPs heard that a tow line, which had been doubled in strength for the job of taking the rig from Norway to the Mediterranean, broke while the Transocean Winner and its tug were off the Western Isles.
Dave Walls, operations director at the rig's owner Transocean, said the towing operation was only undertaken after a risk assessment had been made.
The assessment included checks of the weather forecast for the route.
Mr Walls said planning for towing operations always looked at ways of avoiding an emergency situation from occurring.
He said it was standard not to consider the availability of coastguard ETVs because it could never be known where they might be deployed.
Mr Leusink said that given the conditions the grounding could not have been prevented, though he did say that having an ETV available in the Western Isles may have been useful.
Hugh Shaw, Secretary of State's Representative for Maritime Salvage and Intervention, told the committee that at one point it looked as if the rig might miss coming ashore at Dalmore, near Carloway, on Lewis.
The rig is now being broken up for scrap at a yard in Turkey.
The 17,000-tonne structure came ashore at Dalmore, near Carloway on Lewis, in a storm while being towed to the Mediterranean.
It was later refloated and anchored at Broad Bay, Lewis, before being put on board the heavy lift ship Hawk.
The rig was first taken to Malta before being transported to Turkey.
The rig's grounding on 8 August sparked pollution fears due to the 280 tonnes of diesel on board.
Investigations found two of its four fuel tanks were damaged in the incident which resulted in the loss of 53,000 litres of fuel, most of which is thought to have evaporated with no damage to the environment.
Three weeks later it was towed to the safer anchorage at Broad Bay before being floated on to the deck of the Hawk, a semi-submersible ship used for transporting large maritime structures over long distances.