SwAM:s work with shipwrecks 2017-2018
Four of the 30 most environmentally hazardous shipwrecks in Swedish waters - Thetis, Sandön, Hoheneichen and Skytteren have been examined during 2017 and 2018. Oil recovery operations have been carried out in three cases. The Swedish Agency for Marine and Water Management (SwAM) will continue its work on shipwrecks during 2019, which includes inspection, and recovery of oil and ghost nets.
Oil leakage from shipwrecks primarily affects animals and plants living near the wreck but the oil can spread to other areas with the currents. Toxic substances such as oil, polycyclic aromatic hydrocarbons (PAH:s) and heavy metals are absorbed by for example microorganisms which in turn transfer them up in the food chain to fish and crustaceans.
There are about 17 000 shipwrecks along the coasts of Sweden, 300 of them have been classified as hazardous for the environment by the Swedish Maritime Administration (SMA) in collaboration with SwAM, the Swedish Coast Guard, the Swedish National Maritime Museums and Chalmers University of Technology. 30 of them pose an acute environmental threat since they contain large amounts of oil, which may leak out of control. It occurred in 2014 when the shipwreck Immen, located near Gotland, suddenly started leaking oil. It also occurred in the end of 2018 when the shipwreck Finnbirch started to leak oil from a bunker tank, which still contains 85 m3 of diesel.
Our focus on working with hazardous shipwrecks
- SwAM has since 2016 had the responsibility to coordinate the investigations and the recovery of oil and ghost nets from shipwrecks. The working group that work with the risk assessment and the salvage of oil from wrecks include the Swedish Maritime Administration (SMA), the Swedish Coast Guard, the Swedish National Maritime Museums, the Swedish Armed Forces (the Navy) and Chalmers University of Technology.
- The government of Sweden decided in 2018 to invest SEK 25 million annually for ten years, totally SEK 250 million, to reduce environmental risks from wrecks along the coasts of Sweden. According to the government, between one and three wrecks can be remediated per year. SwAM has been assigned to coordinate the work. The risk assessment of the shipwrecks is made with the probabilistic risk assessment tool VRAKA, which has been development by Chalmers University of Technology. Prior to deciding which wreck to choose for the next recovery operation of oil, SwAM evaluates the probability of a leak, the volume of oil in the wrecks and where the oil is most likely to end up if an oil spill occurs.
Thetis - a pilot project
In the autumn of 2017, SwAM pumped up 730 litres from one of the 30 most acute hazardous shipwrecks, Thetis, which sank in 1985 outside of the island of Smögen on the west coast of Sweden. The remediation was a pilot project with financial support from the Swedish Environmental Protection Agency’s budget for contaminated areas. The oil removed from Thetis was sent to a company that handles environmentally hazardous waste.
During the operation, divers detected a 20 tons purse seine (a type of fishing gear that is placed around a shoal of fish) on and alongside the shipwreck. The size was about 100 x 400 meters and made out of nylon.
Derelict fishing gear and ghost nets can continue to fish under a long time and affect fish and shellfish stocks. The plastic material in the nets slowly degrades into very small plastic fragments, which may be harmful to marine organisms.
Approximately 12 tons of purse seine could be recovered from Thetis during 2018 and was later transported to Fiskareföreningen Norden in Smögen for recycling.
Sandön and Hoheneichen
During the autumn of 2018, two more shipwrecks considered as an acute environmentally hazard were subjected to an on-site investigation and possible oil recovery operation. The wrecks, Sandön and Hoheneichen, are situated approximately 12 to 22 kilometres from the coast of Skåne.
Simulations with the oil spill forecasting tool SeaTrackWeb showed that an uncontrolled release of oil from these wrecks would have ended up near Kåseberga and Ale stenar, and then move towards the city of Ystad. In addition, there are two nature reserves in the area, Norra Sandskogen and Hagestad. The area of Sandhammaren-Kåseberga is also classified as a Natura 2000-area according to the European Union’s Birds and Habitats Directive.
No leakage has been detected or reported since the wreckage of the ships and in August 2018, the Coast Guard did a video survey that showed that the wrecks were intact without any major damage to the bunker tanks.
The work with the on-site investigation and oil recovery operation on the two wrecks lasted for two weeks in November 2018. Several holes were drilled in the hull at the position of the oil and ballast tanks according to the drawings. Despite this, no oil was found in the wrecks, which indicates that the oil has leaked out over the years.
Divers from the Navy examined Skytteren
In 2018, SwAM carried out a major operation at the shipwreck Skytteren together with the Swedish Armed Forces (the Navy). Skytteren sank on April 1, 1942 at Måseskär outside of Lysekil, in an attempt to bring munitions to the allies. Estimations suggest that there are 400 - 500 cubic meters of oil left in the wreck.
Skytteren is located at a depth of approximately 74 meters, in an area with strong sea-floor currents. SwAM considered therefore that the Navy’s divers where the most suited for the mission. The investigation was carried out between 14th to 21st of November with the help of the Submarine Rescue Vessel HMS Belos.
Deep divers participated from The Swedish Armed Forces Diving and Naval Medicine Centre, the 1st Submarine Flotilla and the 4th Naval Warfare Flotilla, as well as doctors and nurses for medical preparedness.
The purpose of the diving sessions was to increase the knowledge on how to perform risk assessments on environmentally hazardous shipwrecks and to assess the status of Skytteren, specifically. A detailed examination of the wreck, measurements of the hull thickness and measurements of water parameters were performed. No oil was recovered during this operation.
The shipwreck initially seemed to be in relatively good condition but measurements on the hull plates showed that they were corroded and in some parts only 5-6 millimetres thick, which is less than one third of the original thickness. On the sea surface, a small but continuous oil spill was also detected. It was not possible to trace the leak back to a specific position on the wreck or to draw any certain conclusions on how much oil is left in the wreck during this operation.