Published 27.6.2023

The Geological Survey of Finland carries out seabed soundings in Metsähallitus’s offshore wind power projects

Metsähallitus will launch four new offshore wind farm projects this year and next year. Preliminary studies and preliminary project development are currently being carried out in the relevant areas. An important part of the preliminary studies is the sounding of the seabed with another state organisation, the Geological Survey of Finland GTK, which Metsähallitus has selected as its partner after a tendering process.

The soundings will start in Närpiö today (27.6.2023), and in front of Pyhäjoki and Raahe and Siikajoki initial around mid-July. The sounding of one area will take around three weeks, but the work is very weather-sensitive.

The area to be sounded for one offshore wind farm is approximately 120 to 230 km². The water depth at the area is mainly around 10 to 45 metres. The offshore wind power areas to be sounded are located in public waters in the Gulf of Bothnia.

“Seabed sounding provides valuable information for the construction of offshore wind farms and the placement of the submarine cable as well as for nature surveys. In addition to the contours of the seabed, it is essential to define some significant geological properties of the seabed, such as depth and soil type thickness. For example, sounding data helps to determine where wind power plants or other offshore wind farm structures can be placed and what kind of foundations are needed for wind power plants,” explains Ville Koskimäki, Wind Power Project Development Manager at Metsähallitus.

The sounding equipment to be used will provide information on the depth variation of the seabed, the quality and thickness of the seabed layers, and any other objects on the seabed. The strength of GTK is their decades of experience in sediment studies in the Finnish coastal area, in which material produced by acoustic seismic soundings has been compared to a series of several meters long samples bored from the seabed. This way, GTK has accumulated a unique seabed geodatabase over the years, with which the sounding material gathered from the new research areas can be compared.

“The sounding is a demanding phase because the company that is selected as our partner in the construction and operation of the offshore wind farm will design the structures of the power plants based on the information gathered at this phase. As project development progresses, the characteristics of the seabed will be examined in more detail,” says Koskimäki.

“GTK’s tasks also include the processing of data produced by sounding so that it can be used for permit applications and planning of the wind power farm areas, assessment of risks related to the seabed and for informing the authorities,” Koskimäki lists.

Further information

Ville Koskimäki, Wind Power Project Development Manager, Metsähallitus,, +358 40 536 9582

Sami Jokinen, geologist, GTK,, 029 503 2211