Construction of the project will involve detailed, specialist engineering techniques. The main principles are outlined below.

Wind turbines

We are proposing to use three-bladed wind turbine generators. These will include the following elements:

  • Rotors, including blades and a hub (connects the blades to the shaft and drive train).
  • Nacelle, which houses the electrical generator, control electronics and drive system.
  • Structural support, which includes a tubular steel tower on top of a foundation structure.

The layout and design of the wind farm

The exact layout of the wind turbine generators is still being developed and will not be finalised until the project has been granted consent by the Secretary of State for Energy Security and Net Zero.

Wind turbine generators will be set out in two ‘lines of orientation’ through the array area and our wind turbine rows will be orientated roughly north to south. In-row (the space between each individual wind turbine generator in a row) and interrow (the space between each row of wind turbine generators) spacing will be a minimum of 1400 metres.

To promote co-existence with fishing activities, we are committing to maintaining an area that will be free of wind turbines and offshore substation platforms.

Connecting offshore to onshore – Transition Joint Bays

The offshore export cables will connect to the onshore export cables at up to four Transition Joint Bays (TJBs).

The onshore TJBs will be located above Mean High Water Springs in farmland to the south of the A547.

Fast facts: wind turbine generators

The below information is based on current understanding and may be refined once consultation has closed and ahead of submitting our DCO application. These numbers are assuming the generation of 1.5GW of electricity.

  • Proposed number of wind turbine generators: up to 96
  • Proposed rotor diameter: 320 metres
  • Proposed tip height of wind turbine generators: between 293 and 324 metres above the lowest astronomical tide (LAT)
  • Proposed rotor clearance above LAT: 34 metres

Fast facts: Offshore Substation Platforms

  • Proposed maximum number of OSPs: 4
  • Proposed maximum topside width (’topside’ meaning the main structure on top of the foundations above the sea surface): 60 metres
  • Proposed maximum topside length: 80 metres
  • Proposed highest point of topside (above LAT), excluding the helicopter landing pad and lightning protection: 70 metres

Onshore cables

The Mona Onshore Cable Corridor will be approximately 18km in length and the cables will be buried underground. Having collated all consultation feedback, the Mona project team have now chosen our single onshore cable route and will be talking to landowners over the coming months, so that we can continue to refine down our cable corridor to one that is approximately 75m wide.

The map on the Onshore Substation tab illustrates these refinements.

The Mona Onshore Cable Corridor width will need to allow up to four cable circuits to be installed, but we expect this width to be reduced in some areas ahead of submitting our application, following further surveys and studies.

Once the cable installation work is completed and commissioned, the temporary haul road will be removed and the ground reinstated using stored subsoil and topsoil. All temporary construction compounds and temporary fencing will be removed, field drainage and/or irrigation will be reinstated and the land will be restored to its original condition. Where practicable, consideration will be given to early restoration of sections of the Mona onshore cable corridor.

Hedgerows will be replanted using locally sourced native species, where practicable. Suitably qualified and experienced contractors will be used to undertake the reinstatement, which will be based on restoring the hedge to match the remaining hedgerow at each location. Where appropriate, some enhancement (such as planting of additional suitable species) may be undertaken.

Onshore substation

A construction compound will be required at the Mona onshore substation. The compound will be located within the Mona Proposed Onshore Development Area and will provide offices, welfare facilities, storage of plant and equipment and parking for construction staff.

It is anticipated that construction access to the onshore substation site will use the proposed permanent access route, albeit that during construction, a temporary surface may be used. This access route will need to be installed early in the construction process.

The onshore substation building substructures are likely to be composed of steel and cladding materials. The structural steelwork will be fabricated and prepared off site and delivered to site for construction.

Prior to the commencement of all of our onshore works, a number of preconstruction surveys and studies will be undertaken to inform the design teams when developing the final design, including:

  • Archaeological pre-construction work
  • Ecological pre-construction surveys
  • Geotechnical investigations
  • Drainage studies

Further work

We will now be looking at potential construction and operational access options, as well as preparing a landscaping and planting strategy to mitigate potential visual impacts of our onshore substation. We are also still refining the size, layout and height of the onshore substation buildings, in response to consultation feedback received.

Similarly, the project is now working to refine our detailed proposals for the onshore cable route including our access strategy for construction vehicles and the location of construction compounds. We are also determining the most appropriate ways for the route to cross roads, utilities and environmental receptors, such as watercourses.

Code of Construction Practice

All construction will be undertaken in accordance with a Code of Construction Practice. The CoCP will set out the key management measures that we will require all our contractors to adopt and implement for all relevant construction activities for the onshore elements of the Mona Offshore Wind Project.

The CoCP will be developed in dialogue with our stakeholders. It will remain a draft document during our consultation, application stage and through the Examination process, and will be finalised when we have a detailed design post-consent. Implementation of the CoCP will be secured through the DCO requirements.