Ørsted proposed the development of the Hornsea 04 Offshore Wind Farm, a major addition to the Humber offshore wind cluster. Positioned approximately 69 km east of Flamborough Head, adjacent to the eastern boundary of the existing Hornsea 02 array, the project would have been one of the world’s largest offshore wind farm developments.
The selected landfall, located near Fraisthorpe, south of Bridlington on England’s east coast, lies within a zone of significant active coastal erosion. Ørsted identified landfall construction as a high risk element of the project and sought specialist assessment to establish a ‘base case’ export cable landfall design to take forward with EPCI contractors.
Our geotechnical team carried out a comprehensive Landfall Feasibility Study. The objective was to technically evaluate trenchless installation options capable of meeting Ørsted’s base cable installation parameters, enabling a clear and informed decision on the lowest risk solution for the project and providing a robust reference design for the main works tender.
The study included a detailed geological assessment and ground modelling based on ground investigation data, alongside the specification and procurement of topographical surveys. Using both onshore topographic information and offshore bathymetry data, 3D landfall profiles were developed to support the assessment of installation constraints, including minimum water depths at punch out and cable cover depth requirements for thermal dissipation.
A long term assessment of coastal erosion potential, projecting conditions up to 45 years post commissioning, was undertaken with technical support from a sub consultant. Our team also carried out inspections of rock core samples recovered from offshore boreholes to determine the frequency and nature of flint inclusions, which could pose challenges for trenchless construction techniques.
To support risk management and future project stages, a comprehensive Geotechnical Risk Register was developed, identifying key ground related risks and proposing appropriate mitigation measures. The findings were formalised through the production of a detailed Landfall Feasibility Report and associated base case design drawings.
Our analysis demonstrated that the lowest risk technique would be a fully cased system, driven from onshore to offshore using a jacked microtunnel boring machine launched from an onshore sheet piled pit. This solution provided confidence in achieving the required length to meet minimum water depth criteria at punch out, while limiting the extent of offshore works and associated weather dependency. Subsequent engagement with EPCI contractors by Ørsted validated this recommendation.
