On Tuesday, the UK Maritime and Coastguard Agency said that there was little risk of pollution from the grounded semisubmersible rig Transocean Winner, which went onto the rocks near Carloway on the Isle of Lewis early Monday morning.
The Winner has 280 tonnes (or about 90,000 gallons) of diesel on board, and authorities have been monitoring the site for signs of pollution. So far none has been observed.
GVA, the designer of the GVA 4000 series rigs (including the Winner) suggests in specifications and consultants' reports that drilling mud, brine and ballast tanks are located in the vessel's pontoons, the structural elements resting on the rocks. The firm was not immediately available for comment.
SMIT Salvage has been contracted for the response effort, and a team of SMIT salvors was set to make an initial inspection of the rig on Monday.
"This initial recce will be checking a number of things including fuel tanks," said Hugh Shaw, the on-site representative of the UK Secretary of State. "Weather permitting, it’s then intended to put a second larger group of salvors on tomorrow to carry out a more detailed inspection."
The UK Coastguard asked local residents and tourists to stay away from the popular beach and headlands areas near the grounding, for their own safety but also to ensure ease of access for emergency response crews.
The UK Marine Accident Investigation Branch has launched a formal investigation into the incident. So far, it is known that the Transocean Winner was in transit, towed by the anchor handling tug Alp Forward, when the tug lost the tow in severe weather. The Alp Forward was unable to reestablish a connection and high winds blew the Winner aground early Monday.
The 1983-built Transocean Winner has a 65-foot transit draft and a transit displacement of 20,000 tons.
As of Transocean's latest fleet status report, the rig was scheduled to come off contract with Marathon Oil last month. The BBC reported that it was under tow from the North Sea to Malta at the time of the grounding; Valletta-based firm GANADO Advocates recently reported that Transocean is stacking rigs in Malta while determining which and how many to scrap at Turkish recycling yards.