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The Baltic Sea seabed surveys along the entire length of Harmony Link (approx. 300 km), which began in February 2021, has been completed. This is a milestone on the new interconnector between Poland and Lithuania – one of the largest investments in transmission infrastructure in this part of Europe. Due to possible unforeseen difficulties (e.g. storms) during carrying out the surveys, this was a crucial part of the project schedule. What does the completion of this part mean for the whole investment? ILF Consulting Engineers Polska (ILF Poland) was the company responsible for supervising the surveys.

The seabed surveys allowed, among others, to determine the locations of wrecks or post-war remnants of conventional and chemical weapons lying on the seabed. The location of obstacles has been included on prepared maps, which will help to avoid dangerous objects at the design phase. A route of about 300 km was surveyed. Side scan sonar and magnetometers were used for the task and bottom samples were taken. Remotely operated vehicles (ROV) took part in the works. The project is realized by PSE and Litgrid, transmission system operators in Poland and Lithuania. ILF Consulting Engineers Polska was responsible for supervising the surveys.

Seabed surveys are a key step in the investment process, highly dependent on weather conditions, which cannot be fully predicted. Therefore, they are an important element of the work schedule.

The survey report will be used to design and determine the final route of the High Voltage Direct Current (HVDC) offshore cable line between Poland and Lithuania, as well as to elaborate its laying and its protection strategy, including the determination of the burial depth of the cable system taking into account seabed conditions. It is ILF Poland that will analyse the possible risks of cable burial (Cable Burial Risk Assessment) on the basis of seabed surveys conducted.

Previously, ILF Poland was responsible for the Baltic Sea seabed routing as well as supporting PSE and Litgrid during the tender procedure for the contractor of the marine survey analysis.

The offshore cable will improve energy security of the region by opening the way to synchronization of Lithuanian, Latvian and Estonian power systems with the continental European system. Harmony Link is the second interconnection between the Polish and Lithuanian power systems – the first LitPol Link line connects Ełk substation in Poland and Alytus substation in Lithuania.

The completed study is a milestone on the Harmony Link project. Works began in February and were completed in August 2021.