Work commences to extract fuel oil from submerged bow tank
Work has started to extract fuel oil from the forward tank of the wreck of the OS 35, the Gibraltar Government said on Saturday evening.
The extraction operation suffered a setback earlier in the afternoon after the ship’s engine room flooded, preventing salvors from using onboard machinery which remains out of use.
Some of the water has been pumped out of the engine room and divers are working to identify the source of the leak, but hull deterioration in that area means flooding could “realistically increase” at any time.
To stabilise the vessel and add buoyancy, water has been pumped out of a cargo hold to help mitigate the impact on the hull’s structural integrity.
The forward tank containing fuel oil is submerged, further complicating the extraction operation.
But salvors have managed to successfully commence the process, albeit slowly, through a vent in the tank.
Earlier they had completed extraction of fuel oil from the aft tanks, having first removed diesel earlier in the week.
The vessel’s forward No Tank 1 is split into four separate parts, namely port, centre port, starboard and centre starboard.
Very slow extraction has successfully begun from the centre starboard section, where the bulk of the remaining oil – some 80 tonnes – is believed to be located. Salvors estimate the forward tank holds some 126 tonnes in total.
Initial assessments suggest that this tank is damaged by a minor crack that is letting water in.
“The extraction from this tank therefore needs to be done by relying on the pressure of the water entering the tank pushing the oil upwards toward and through the tank vent,” the Gibraltar Government said in its latest update.
“This is a slow process that is managed carefully in order not to increase the amount of water that is mixed in with the fuel when extracted.”
Operations to start the extraction from Tank 1 Centre Starboard were authorised by the Captain of the Port and commenced at approximately 5.00pm and by 7:00pm, some 12 cubic metres of mixed oil and water – about 12 tonnes - had been extracted.
The removal operation will continue through the night.
Separately, the operation to deploy a second containment boom around the wreck is ongoing, although it is described as “a complex operation” in which two large Spanish state-owned salvage tugs, the Luz de Mar and the Clara Campoamor, are playing a key role.
Overhead, a Spanish maritime surveillance aircraft was authorised to fly over the area to provide aerial intellegnce on the location and movement of slicks at sea.
Skimming operations continued through the day, including the recovery of 600 litres of low sulphur fuel oil from the vicinity of the wreck.
These operations will stop overnight but continue at first light.
A purpose-built, small catamaran launch that can operate 24/7 is en route from Cadiz with a double crew but has had to shelter in Tarifa due to high winds. It is expected to arrive on site tomorrow morning.
A Notice to Mariners issued by the Gibraltar Port Authority extended the exclusion zone around the wreck to 500m, to allow additional space for the salvage operation and ensure safety at night as the second boom is not illuminated.
An additional boom has also been placed to protect Sandy Bay.
Clean-up operations continued throughout the day, in particular in Sandy Bay and Little Bay with a focus on cleaning rocks and pebbles as well as raking sand to remove any globs of oil that has washed up.
But so far the impact on shore appears minimal and the Environmental Research and Protection Unit’s latest assessment is that there is no significant increase in soiled birds.
Earlier on Saturday, the Gibraltar Government issued a stark warning that the operation in the coming days would be complex and dynamic, and that furher pollution was likely despite efforts to contain any spillage into the sea.
Even after the tanks are emptied, residual quantities of fuel oil and the vessel’s “crumpled” hull mean continued seepage of small quantities of pollutants are “almost entirely unavoidable” until the vessel is removed.
“The deployment of booms in layers around the vessel will prevent to the highest possible level the amount of seepage into open water but they will not provide a watertight layer of containment, which it is not technologically possible to provide,” the Gibraltar Government said in its latest update.
“In this respect, it should be noted that all options for the salvage operation are sub-optimal in terms of the absolute control of pollution.”
“The aim of layered containment is to limit the seepage as much as possible.”
“It can however not be realistically expected that there will not be some seepage outside the booms into surrounding open water, despite the best possible strategy of layered containment.”
“The advice is that this is the unfortunate but unavoidable situation arising from this incident.”
“This situation will therefore now continue for the rest of the summer and until the salvage operation is completed.”