Fugro’s WAGEO research supports IJsselmeer Lake cable route

Gathering detailed waterbed structure insights

The Blue Wind Plan (Windplanblauw) is an ambitious renewables project in the Netherlands. Involving the replacement of 74 existing onshore and nearshore wind turbines with 61 larger and more powerful versions. 

As part of this project, 28 existing nearshore wind turbines at the Irene Vorrink wind farm had to be demolished and the foundations for 24 new replacement turbines installed.  

The client, Vattenfall/SwifterwinT, required accurate geophysical measurements to support the design of the cable routes between the 24 new turbines and the mainland. These measurements would also be available to support the design of cables and turbine foundations.  

Lake IJsselmeer soil profiling

To collect the geophysical data, our survey boat spent 6 days profiling approximately 30 kilometres of the soil structure below Lake Ijsselmeer, an inland bay that borders the provinces of Flevoland, North Holland and Friesland in the central Netherlands. 

The boat dragged a specially designed streamer (a measuring cable with 24 electrodes) over the lakebed, while measuring electrical resistivity at various distances between the electrodes.  

Our unique on-board WAGEO technology used electrical resistivity tomography (ERT) to measure electrical resistance in the soil, as well as variations in particle size, clay ratio and the conductivity of the water in the soil. 

By analysing the resistance patterns, WAGEO was able to distinguish between the clay, silt, sand and gravel layers in the lakebed, and to map them out precisely. We positioned the measurements accurately using real-time kinematic global positioning satellite (RTK-GPS) technology. 

This approach delivered rapid results. WAGEO provided a continuous 2D image of the electrical resistivity contrasts of the soil, to a depth of around 15 to 20 metres below the waterbed. We then calibrated the measurement data, based on the available geotechnical information, drillings and cone penetration tests (CPTs) for the design of the cables that would be needed to transport the generated power. 

Our Geo-data experts then applied in-house software to convert the data into 2D or 3D length profiles. Vattenfall/SwifterwinT used our measurements to help determine the optimal routes for the cables, as well as to refine the designs of the cables and the turbine foundations. 

Speed wasn’t the only advantage brought by the WAGEO approach. Additional benefits included low CO2 emissions and limited disruption of the soil, local flora and fauna. 

Innovative highlight: WAGEO geophysical technology

WAGEO is an innovative, non-destructive geophysical survey technology designed to capture accurate data in a fast and efficient way. It can be applied in water up to 50 metres deep, so it’s ideal for projects that need accurate insights on waterbed structure.  

Different soil and rock types, like gravel, sand, clay, peat and silt, each have their own electrical resistivity ‘signature’. WAGEO uses electrical resistivity tomography to constantly provide an image of the various soil layers in the lakebed.  

Based on the measured electrical resistivity contrasts and existing point measurements as CPTs and/or drillings, we made statements about the soil structure below Lake IJsselmeer, which Vattenfall/SwifterwinT applied to the cable route design. 

Impact

Speed and accuracy were of the essence for this important energy infrastructure project. Using WAGEO technology enabled us to achieve on-time delivery of the required insights into the lakebed structure, backed up by a wealth of calibrated measurement data. 

The project progressed according to plan. With the completion of the demolition work at the Irene Vorrink wind farm in 2022, turbine foundations and cable-laying in 2023, the turbines were constructed in 2024. 

The entire Blue Wind Plan is completed in 2024. It generates enough power to meet the annual electricity consumption of 450,000 households – the switch to renewable energy will annually save around 700,000 tons of carbon emission in total.