Clearing oil from the wreck of the RFA Darkdale will be challenging and costly – but clearing up an environmental disaster would be worse.
The Ministry of Defence is keen to avoid coping with an oil slick in mid-ocean, like the one caused near Tristan da Cunha by the loss of the MS Oliva in 2011.
The MoD’s report on the Darkdale says: “There are no publicly available figures for the total cost of the clean-up for [the Oliva] incident. However given the response that was mobilised, the figure will be several million pounds.”
The same could be true of a major leak from the Darkdale. “If no positive action is taken to remove the oil, the MoD must be prepared to mobilise a large scale response when the wreck releases the oil, and bear all the costs of this action.”
But it knows it can be done – because it has already tackled the same challenge with the wreck of the HMS Royal Oak, which was sunk by a U-boat in Scapa Flow, in the Orkney Islands, in 1939, with the loss of 914 lives.
Like the Darkdale, it began leaking oil at a growing rate as its hull corroded. Both ships lie in similar depths.
A technique known as hot-tapping was used to remove 1,500 cubic metres of oil from the Royal Oak.
This would involve sawing a hole into the Darkdale’s remaining tanks so the oil could be drawn off carefully.
“The structure of the Darkdale is a simple single-hulled tanker, making hot-tapping considerably easier than on a warship,” says the MoD’s December 2013 report.
“Much of the difficulty and time spent removing oil from the Royal Oak was due to the large number of small compartments and defensive design features such as the torpedo bulge.
“The Darkdale does not have any of these features.”
Disposing of the oil waste will need careful thought, says the report.
And there remains a danger from wartime shells, it says. “A detailed assessment of the unexploded ordinance risk would have to be undertaken and it is likely that the shells lying around the wreck would have to be removed and disposed of.”
St Helena’s remoteness will add greatly to the costs.
In other respects, the emptying of oil from the Royal Oak may have been far more delicate, judging from a report on the website of the contractor, Briggs.
“Spaces adjacent to bunker tanks were containing sensitive munitions and human remains,” it says.
The ship’s status as a war grave had to be respected throughout the operation.