Questions and answers about shipwrecks

There are about 17 000 shipwrecks along the coasts of Sweden. The Swedish Maritime Administration (SMA), SwAM, the Swedish Coast Guard, the Swedish National Maritime Museums and Chalmers University of Technology have classified 300 of them as hazardous for the environment. About 30 of these pose an acute environmental risk.

Some of the shipwrecks leak oil and other hazardous substances already and may adversely affect fish and other aquatic animals. Organisms living in the vicinity of the shipwrecks are mainly affected. Hazardous substances like oil, polycyclic aromatic hydrocarbons (PAH:s) and heavy metals are taken up by microorganisms which can transfer it up the food chain to fish and crustaceans.

Several shipwrecks contain large amounts of oil which can cause damage in large areas when it leaks out. Oil spills and leakage of other hazardous substances can also affect tourism, the fishing-industry and aquaculture.

The remediation of oil spill is very expensive. A bigger oil spill of 500 tons oil had a cleanup cost of SEK 140 million for the municipality of Orust, in the Swedish west coast in 2011. Furthermore, a leakage of about 20 cubic meters of oil in 2017 had a cost of SEK 2,4 million in total for the municipalities of Tanum and Lysekil. Loss of income from decreased tourism and economical costs for adverse effects on the environment were not included in the calculations. Tourism has an annual turnover of billions of Swedish crowns and even a small decline can have a large impact on the local economy. Therefore, it is beneficial for society to carry out preventive oil recovery operations on environmentally hazardous shipwrecks, in terms of both economy and the environment.

From 2016, SwAM has the responsibility to coordinate investigations and recovery operations of oil and ghost nets from shipwrecks. SwAM leads a national working group on risk assessment and remediation of wrecks. The group includes the Swedish Maritime Administration, the Swedish Coast Guard, the Swedish National Maritime Museums, The Swedish Navy and Chalmers University of Technology.

The Swedish Maritime Administration makes hydrographic surveys with side scan and multibeam sonar to control the status and location of the shipwrecks (multibeam sonar sends out multiple audio signals that hit the shipwreck and bounce back, a three-dimensional image of the wreck can then be created in a computer).

The Swedish Coast Guard and the Swedish Navy dive and film the shipwrecks to obtain more detailed data and to assist in evaluating the environmental risk they pose. The Swedish National Maritime Museums assists with gathering the history regarding the shipwrecks and Chalmers University of Technology contribute with the development of the risk assessment tool VRAKA (probabilistic risk assessment of shipwrecks).

The work starts with a thorough investigation and mapping of the shipwreck, including a localization of the oil. When the wreck is to be emptied of oil, the hull is penetrated in a closed environment, that is, the oil does never enter the aquatic environment. The work is performed by divers or ROVs.

After the penetration of the hull, a flange with valve is mounted and the oil is pumped up to tanks on the operator's vessel. The holes are then sealed. The oil is then left for destruction, or may in some cases be reused after passing a refining process in an oil refinery.

The government invests SEK 25 million a year for ten years, a total of SEK 250 million, to reduce environmental hazards from shipwrecks along the coasts of Sweden. According to the government, between one and three environmentally hazardous shipwrecks can be remediated each year. SwAM is responsible for carrying out this investment in the environment by prioritizing which shipwrecks that will be subject to detailed investigation and subsequent recovery of oil and ghost nets. The prioritization and the risk assessment is carried out with the risk assessment tool, VRAKA, developed by Chalmers University of Technology. See the location of the 30 most environmentally hazardous shipwrecks on our webpage.

During 2017 and 2018, recovery operations were performed on the shipwreck Thetis, near Smögen on the Swedish west coast, and oil and a ghost net (purse seine) were recovered. Oil recovery operations were also performed on the shipwrecks of Sandön and Hoheneichen near Ystad.

Furthermore, during 2018, SwAM in collaboration with the Swedish Navy, also performed a large diving operation and detailed examination of the shipwreck Skytteren, near Lysekil on the Swedish west coast.

The Swedish Coast Guard and several companies have previously recovered environmentally hazardous substances from wrecks where an owner was identified and insurance arrangements could be used. However, the remediation of the shipwreck Thetis was the first time a Swedish governmental authority developed a model for recovery of oil and ghost nets from an older, ownerless wreck, and then performed an oil and ghost net recovery operation on the wreck.

Thetis is one of the ~30 shipwrecks classified as an acute environmental hazard. Before the oil recovery operation, it was estimated that the wreck could contain up to 22 cubic meters of oil, which is ten times more than what fits in an oil storage tank in a typical Swedish residential home. It was also established that the wreck had begun to leak oil in smaller amounts. Thetis is located near a sensitive archipelago, both in terms of the marine environment and beach areas. Further out to sea, lies the protected area of ​​Bratten, with large numbers of red-listed threatened species, several of which have their only or main occurrence in Swedish waters.

Furthermore, Thetis is located at a depth of 30 meters, near a port and is in relatively good shape. It was therefore suitable as a pilot project for the recovery operation.

The oil that is recovered during an operation is sent to an enterprise with appropriate permits, for example an oil port or another company that can receive and recycle environmental hazardous waste.

In most cases, the oil in the shipwreck is located and removed, instead of the whole wreck being salvaged. Several wrecks are in very bad condition due to corrosion and the risk of a collapse during a salvage operation would therefore be imminent. Such a collapse of the wreck could cause an uncontrolled leakage of oil. The work with environmental hazardous shipwrecks in Swedish waters will therefore entail that oil is recovered from the shipwrecks while the wreck itself remains on the sea floor.

When the oil is removed, the shipwreck does not pose an environmental hazard anymore. On the contrary, it can act as a structure that has a positive impact on the environment by forming an artificial reef, which can attract fish and other marine organisms.

SwAM has seven operators on contract that recover oil and ghost nets from shipwrecks. To obtain a framework agreement through the Swedish Public Procurement Act, the operators needed to demonstrate that they were capable and had the ability and experience to recover environmental hazardous substances from shipwrecks. Prior to every new project, a reopening of competition under the framework agreement is carried out, where the operators may submit a tender for the oil recovery operation. The operator with the most economically advantageous tender is offered the contract and may carry out the oil recovery operation.

To check if there is oil left in the shipwreck, holes are drilled through the hull at the position of the bunker tanks. A visual inspection with divers or ROV is not enough, it only provides a general picture of the position of the wreck and what condition it is in. If there is great damage to the double hull, it can be assumed that the oil has been discharged, but if the hull and structure of the wreck are in good condition, an oil recovery operation must be carried out.

SwAM has investigated the possibility of physically examining whether there is oil left in a wreck prior to deciding on an oil recovery operation. There are then two options: 1) to drill small holes in the hull and see if oil "bubbles" out or 2) to use "neutron backscattering technique" (neutrons are sent in through the hull using ROV) to detect oil. There are risks and weaknesses with both techniques. There is a risk that the corroded hull of the shipwreck can rupture if one performs the first option and drill holes. If an oil spill then occurs, without having an initiated and informed organization with capabilities of recovering oil, for example initial capabilities of the operators or the Coast Guard, the spill can inflict great environmental damage and in the end become very expensive.

Furthermore, it is uncertain that drilling small holes to see if oil leaks out works if the oil type solidifies under cold conditions, for example as with heavy fuel oil. Oil will then not be discharged and an incorrect conclusion will be drawn that there is no oil left in the shipwreck.

A limitation of the second option, the use of the neutron backscattering technology is that it works poorly if there is only oil or water in a tank. The best results can be obtained if there is both water and oil in the tank, and differences can be detected. Another limitation is that if the shipwreck has a double hull, the technique will not work if you do not drill or cut through the first hull and then measure through the second hull. This implies a much larger operation. The area on the hull where measurements are to be carried out needs to be cleaned from biological growth and rust, in order to enable the instrument to get a good signal. This imply great workload for divers or ROV. The rental costs of the instrument, the work vessels and the personnel would be substantial.

SwAM does therefore choose the precautionary principle and assumes there is oil left in the shipwrecks classified as environmentally hazardous, if no other data is available. Even if only a few shipwrecks would contain oil, the investment in oil and ghost net recovery from environmentally hazardous shipwrecks results in an economic and environmental benefit for society.

Most of the hazardous shipwrecks that SwAM works with have no owner. The company that once owned the ship may have been dissolved, gone bankrupt or does not exist any longer for any other reason. So there is no owner to claim responsibility from. If the vessel wrecked before 1969, liability under Chapter 10 of the Swedish Environmental Code cannot be demanded either, since the Code is not applied to activities before -69. The statutory limitation period according to the Swedish maritime code (Chapter 10) for oil or bunker oil damage of three years from the date on which the damage occurred, or at the latest within six years from the date of the accident. In many cases this period has already expired.