Shipwrecks from both world wars litter Estonia's territorial waters and over time more and more fuel leaks are expected. Until now, the state has responded to pollution incidents as the work is complex and expensive.
Ivar Treffner, a researcher at the Estonian Maritime Museum, told Vikerraadio's "Ökoskoop" that the exact number of wrecks in Estonian waters is unknown.
"There are dozens of known environmentally hazardous wrecks. These are ships that were already using liquid fuels, not coal or sails," he explained.
One recent example, Treffner highlighted was a German T30 fighter which sank in 1944 near Narva and began to leak a few years ago. A large-scale cleaning operation was organized by the authorities.
"What is already leaking again is the Cassandra wreck from the First World War, which sank near Saaremaa. When we went there, we found oil bubbles rising to the surface, which turned into oil slicks when they mixed with water," he said.
Cassandra is a 130-meter British light cruiser that came to the aid of Estonia during the War of Independence, but ran into a sea mine and now sits at on the bottom of the Baltic Sea.
"She lies about 25 nautical miles from the island of Vilsandi towards Sweden. It's not very close to the shore, which makes it more difficult to track," Treffner said.
Based on witness testimonies, it is assumed that despite the mine explosion, the fuel bunkers probably remained intact.
Cassandra bunkered in Copenhagen before arriving in Estonia, and since it was accompanied by other ships of the same class, it can be deduced how much fuel Cassandra carried with her.
"It can be assumed that the fuel was the same and the fuel consumption was more or less the same. We have log extracts from other ships. Cassandra's log went down with the ship, but we know that she may have contained between 710 and 780 tonnes of fuel. Maybe something came out at the moment of sinking," the researcher said.
Pumping fuel out is difficult and expensive
Treffner said removing the fuel from a wreck like Cassandra is difficult because it is located at a depth of 95 meters and is quite far from the nearest coast.
"She's lying on her side, so won't have access to all the bunkers anyway. In an ideal world, of course, such wrecks would have to be pumped dry. On the other hand, you always have to look at what it costs. Let's just say that such an operation is not exactly cheap," he noted.
The Police and Border Guard Board (PPA) periodically conducts overflights of Cassandra and other pollution-prone wrecks, but Treffner said it is quite difficult to organize active monitoring.
"It is highly unlikely that they will run out all at once, one would hope that the ship will signal before they do. The question then is also how fast catching it will take and where the spill will occur. Cleaning up pollution at sea is about ten times cheaper than doing it on the beach, " the researcher said.
How do you even get fuel out of sunken ships? Treffner said taps are drilled into the ship's hull which are connected to hoses. Hot water is then poured in to dilute the fuel and flushed out. "The metal corrodes and becomes progressively softer. If the body is already very old and brittle, the taps can no longer be put on and other solutions have to be found. There are different options," he said.
As old warships also contain unexploded ordnance, they pose a danger to divers. Therefore, it must also be neutralized or removed before fuel is pumped out. Old fishing boats can also cause problems for divers who can become entangled in their nets.
"These same nets continue to catch fish after the ship sinks. You go and look, seals, fish; the wrecks are just thick with them," the maritime museum researcher said.
Navy: Number of leaks could skyrocket at some point
The navy is responsible for pollution control in Estonia's waters. Mati Kose, the Navy's chief specialist in pollution control, said many shipwrecks originate from the First and Second World Wars.
"Due to their age, there is a risk of damage or collapse to the hulls and structures of ships, which could also lead to oil spills and marine pollution," Kose told Novaator.
"In recent years, small to medium-sized wreck leaks have been detected, but there is no evidence that their frequency has increased significantly," he said, adding reports from sunken warships are far below those connected to modern cargo ships.
But he said: "At the same time, it cannot be ruled out that, for historic wrecks, at some point in time, the oil spills into the sea caused by these wrecks could increase dramatically."
Kose said the Navy primarily responds to pollution reports but it is gradually trying to be more proactive and identify wrecks in danger of leaking.
"As sunken warships are often accompanied by unexploded ordnance, it is best to carry out an environmental risk assessment of the wreckage and, if necessary, to pump out the tanks in cooperation with the Navy and other relevant authorities. Given that the National Hydrographic Survey's seabed and survey finds 10-20 more wrecks each year to add to the approximately 500 known shipwrecks, it is appropriate to consider launching a national program of activities and funding," said Kose.
Editor: Rait Piir, Helen Wright
Source: Ökoskoop interview by Kristo Elias