A “catastrophic” oil leak from the wreck of the torpedoed RFA Darkdale has been declared inevitable within 25 years if no action is taken.
Britain’s Ministry of Defence has now promised urgent steps to remove the oil, to protect human health and St Helena’s precious environment.
In the meantime, its investigation team says an exclusion zone should be set up around the vessel.
The ship has been causing low-level poisoning of marine life since it was blown up in James Bay by a German submarine on 22 October 1941, killing 41 men on board.
A severe storm in 2010 apparently caused wreckage to shift and release more oil than usual, prompting pressure on the Ministry of Defence from the governor at the time, Andrew Gurr.
Investigations in May 2012 found that 10 per cent of fish and shellfish around the wreck had contamination above accepted safe levels. They “may be a hazard to human health if consumed”.
Sediment on the sea bed was found to be badly polluted.
A report from the MoD’s investigators has recommended that a 200-metre exclusion zone be set up around the ship to avoid the danger of rupturing oil tanks.
It says the anchors of the RMS St Helena have snagged on the wreck on occasion, and there has been damage from ships’ anchor chains.
The bow section of the Darkdale is estimated to contain between 2,326 and 4,952 cubic metres of oil – enough to pose an “intolerable” threat to the island’s marine environment.
That is up to 500 times the amount thought to have been released in 2010 – when a large slick formed across the bay, prompting the closure of the inshore fishery.
The hulk was examined by a remote-controlled robot device, brought to the island by MoD contractor Salvage and Marine Operations. They operated from island boats, including a Solomon’s barge.
The survey found the wreck lying in two parts, with the stern section lying on its side with substantial torpedo damage. The bow was found to be lying upside-down and in very good condition, given the time under water.
Generally low levels of contamination were found in water samples, but pollution of sediment exceeded Environmental Quality Standards (EQS). Most fish examined had low-level contamination, but about 10 per cent exceeded the safe standard.
Environmentalists who joined the investigation team found a large spill would cause a short-term lethal risk to inshore fish species – some of which are unique to St Helena waters, and already vulnerable.
Oil remaining in the environment would hinder recovery and could cause long-term “sub-lethal” effects.
The investigators have recommended:
- Removal of the oil
- A ban on anchoring with 200 metres
- A ban on fishing over the immediate site
- Analysis of fish from a wider area
- Long-term environmental monitoring
The MoD has secured funding for the oil removal work, which has been made more pressing because of the expected growth of a tourism industry on the island.
The RFA Darkdale was stationed in James Bay as a fuel tanker.
The ship’s tanks had been replenished only days before it was hit by three torpedoes from the U-68 submarine – in the first U-boat attack in the Southern Hemisphere.
The nine survivors included two seamen who were on deck and were blown into the sea, and the ship’s master, who was about to return to the vessel. Others escaped the blast because they were in the hospital in Jamestown.
The names of the dead are recorded on a monument on the seafront.
A memorial service was conducted by the survey team at the start of its visit, with a union flag being laid on the wreck.
Full investigation report