Exploring the wreck of coastal defence ship Ilmarinen in the northern Baltic Sea


An exciting marine research expedition is currently underway in the northern Baltic Sea as experts from the Finnish Environment Institute, the Finnish Border Guard, and the Finnish Heritage Agency embark on a mission to study the wreck of the coastal defence ship Ilmarinen. Sunk in 1941 after colliding with a mine, the shipwreck poses a significant environmental risk due to its estimated 100,000 liters of light fuel oil held in its tanks.

The team aims to assess the potential for an oil removal operation and safeguard the fragile marine ecosystem from any possible oil leakage.

Project Manager Tommi Kontto from the Finnish Environment Institute emphasizes the urgency of the study, stating that any oil leakage from the wreck could pose a danger to the Finnish coast and the Archipelago Sea, which are both valuable marine environments. Therefore, understanding the extent of the risk and planning appropriate response measures are of utmost importance.

The challenging task involves studying the wreck lying at a depth of approximately 80 meters, partially submerged in bottom mud. To prepare for further action, the team will create a 3D model of the wreck using hydroacoustic equipment on the marine research vessel Aranda. Additionally, the wreck will be filmed using the ROV diving robot to gain valuable insights into its condition and surroundings.

Despite the urgent need for potential oil removal, the team will not physically interact with the wreck to respect its status as a grave site, following guidelines on the sanctity of graves. If the decision is made to empty the tanks in the future, measures will be taken to ensure the sanctity of the grave during the operation.

Finland’s territorial waters are home to over a thousand wrecks, with nearly 30 considered high-risk due to potential oil or hazardous substance leakage. Addressing these risks and preserving the marine ecosystem is part of the country’s water protection program, funded by the Ministry of the Environment. The Finnish Environment Institute leads the efforts in monitoring and renovating wrecks that pose environmental threats, while the Border Guard takes charge of rescue operations in case of spills.

The ongoing study of the coastal defence ship Ilmarinen is one of the many initiatives aimed at achieving a good ecological status of the Baltic Sea and domestic lakes and rivers. By reducing nutrient loading, cleaning oil from shipwrecks, restoring water systems, and minimizing harmful substances in urban wastewater, the water protection program strives to safeguard and preserve the precious water resources of Finland and the Baltic region.


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