Rocking and rolling delays oil rig
25 August 2016
The two tugs towing the salvaged Transocean Winner oil rig were forced to slow down when the 17,600 tonne structure started rolling at sea.
The drilling platform was being pulled on a 54 mile voyage between the grounding site at Dalmore on the west coast of Lewis to anchorage at Broad Bay on the other side of the island early yesterday.
Repeatedly swinging from starboard side to her port side, the tow slowed down to a one knot crawl while salvage engineers pressurised previously holed fuel tanks on her bottom base, risking some diesel spilling out, to make the rig safe.
Twenty five of her lower tanks were ruptured and flooded by the grounding in a storm on 8 August. Compressed air is constantly pumping into 16 of the damaged compartments to keep seawater at bay.
Pollution was reported in the rig’s wake by a creel boat lifting crab pots in fishing grounds near the route off the west coast of Lewis. Fishery officers and environmental agencies are contacting the fishing skipper to find out more information.
Increasing the amount of pressurised air in damaged tanks and also ballasting other compartments helped stabilise the listing rig and it continued on its long journey.
As a result the platform arrived off Broad Bay some eight hours later than initially estimated.
Hugh Shaw, the Secretary of State’s Representative for Maritime Salvation and Intervention explained: "The tow has taken longer than anticipated.
"We have been clear from the outset that we would not compromise the operation in any way so I am delighted that the 54 mile transit has been successfully completed without incident."
He added: “There was some slight movement of the rig on passage and the salvors made adjustments using the pressurisation that’s been used for the buoyancy. Once that was implemented the rig settled down.”
“The downside was we had a slight sheen coming off the rig itself and that was coming
from the damaged fuel tanks. We were prepared to accept that and we had aircraft
up measuring the sheen. Very small amounts -
Mt Shaw said the tow kept well away from the creels, having planned its planned course to avoid going near shellfish grounds in the vicinity.
“We are aware there was some diesel out there. The actual investigation into the fishing vessel and the creels is being dealt with by other agencies such as the local fishery officers.”
The platform stood off North Tolsta as last minute adjustments were made to four giant anchors laid on in the seabed in advance.
Three tugs hooked it up to her securing chains after she was slowly eased the last five miles to the anchorage off Shader, Point.
An additional four anchors are required to ensure she does not break free with the tug ER Vittoria steaming back to Aberdeen to pick them up.
