Considering the environment
RWE is working to strike a balance between commercial, engineering, environmental and social considerations in the development of DBS. Survey and assessment work is helping us to understand the local environment and minimise impacts.
Following the introductory consultation held in September 2022, detailed environmental assessments have been undertaken to determine the location and orientation of infrastructure.
The assessments have included:
- Ground investigations to help us with the infrastructure design;
- Access studies for abnormal loads and HGVs and associated construction traffic;
- Flood risk studies;
- Further detailed visual assessment and work around the mitigation of potential impacts;
- Ecology surveys;
- Noise monitoring;
- Archaeology and heritage studies.
The results of the surveys, assessments and studies identify any potential environmental, social and economic effects. These, along with any relevant mitigation measures, are published in the Preliminary Environmental Information Report (PEIR).
RWE is experienced in constructing renewable energy projects, currently operating 10 offshore wind farms across the UK. We aim to be good neighbours, working closely with local communities to ensure the lowest possible impacts from our construction works.
Construction of DBS could start as early as 2026 with onshore construction works likely to start first. The construction phase is expected to take a maximum of seven years, with completion anticipated in late 2029/early 2030.
We have allowed for flexibility in the approach to construction in the PEIR, considering options for building DBS East and DBS West:
- In isolation;
- Sequentially, with a gap of two years between the start of construction at each project.
Before any construction is carried out, pre-installation works will confirm that the seabed is clear of any obstructions. Offshore works can then commence and involve the installation of wind turbines, cabling and offshore platforms.
The most common construction process for wind turbines is:
- A vessel loads and transports the turbine components, delivering them to the project site;
- The tower is installed first and then the blades;
- Each wind turbine installation is likely to take one day, depending on the weather conditions.
Other construction methods include components being loaded onto barges and installed by an installation vessel, which would remain on site for the duration of wind turbine construction.
It is also possible in some cases for wind turbines to be pre-assembled onshore before being transported to site as a single unit.
Before cable-laying operations commence, it will be ensured - through pre-construction surveys - that the route is free from obstructions such as discarded fishing equipment, anchors, wires or ropes.
The majority of offshore cabling will then be buried through a combination of ploughing, jetting or mechanical cutting and the dimensions of the cable trenches will be dependent on the method used.
It is not possible to bury cables in some areas, including in the closest proximity to the wind turbines and platforms. In these areas the cables will be protected using a range of external cable protection systems.
The proposed onshore construction works consist of the installation of buried onshore export cables- primarily by open cut trenching methods, transition joint bays and onshore substations.
The key installation stages of the onshore works are:
- Initial site investigation works and preparation including the stripping and storage of topsoil;
- Construction of cable joint bays;
- Construction of temporary roads, construction compounds, office units and parking areas to facilitate installation;
- Digging of a pipeline trench to the required depth and constructing cable ducts;
- Laying of cables directly in trenches or pulling through the pre-installed ducts;
- Backfilling of trenches with suitable materials to ensure cable electrical/thermal performance and protection;
- Reinstatement works.
The Pacific Osprey completing turbine installation at Triton Knoll.
Onshore and offshore transport movements
A variety of vessels and vehicles will be used during the construction phase, with the exact number and specification known nearer to the time of construction.
The expected modes of transport which will be used include:
- Vessels, such as boats and barges;
- Construction vehicles.
It is likely that both DBS East and DBS West will be operated from the RWE O&M (operations and maintenance) port at Grimsby. The final decision on construction ports will be confirmed prior to the start of construction.
Temporary access and haul roads are proposed to be built onshore to facilitate construction. The roads will run alongside the online cable corridor in order to transport workers and construction materials.
Maintenance, repowering and decommissioning
A programme of monitoring and scheduled maintenance will be undertaken throughout the lifetime of the wind farms to ensure that all offshore infrastructure is maintained in safe working order and to maximise operational efficiency.
Typical general maintenance activities include:
- Wind turbine servicing;
- Oil sampling and changes;
- Battery changing;
- Service and inspections of wind turbine safety equipment, nacelle crane, service lift, high voltage system and blades;
- Foundation inspection and repair;
- Cable repair and replacement;
- Cable remedial reburial;
- Cable crossing inspection and repair;
- Unplanned and planned corrective work.
The design lifetime of the project is expected to be 30 years. Repowering may be considered at or near the end of the design life, once all options for maintenance and repair are carried out.
Repowering involves the replacement of turbines and / or foundations with those of a different specification or design. This could enable the installation of more efficient wind turbines and would be in line with the technologies available at the time. This would allow DBS to continue supplying clean, renewable energy to the UK long into the future.
Any further consents needed for repowering would be applied for at the time.
Maintenance underway at Humber Gateway Offshore Wind Farm
At the end of the operational lifetime of DBS - which will occur once no further repowering can no longer take place - it is anticipated that all structures above the seabed or ground level will be removed.
The decommissioning sequence will generally be the reverse of the construction phase and will involve similar types and numbers of vessels and equipment. The Energy Act 2004 requires that a decommissioning plan must be submitted to and approved by the Secretary of State for Business, Energy and Industrial Strategy, a draft of which will be submitted prior to the construction of the Projects.
Working with the community
The construction and operation of an offshore wind farm can bring significant benefits to the neighbouring areas including jobs, skills and general economic benefits.
As part of our application for development consent, we have carried out a specific socio-economic benefit study to determine the benefits the projects could bring to the local and wider region. This study can be found in Chapter 28 of the PEIR - Socio-economics.
Working with local stakeholders, we will develop a Community Benefit Package for DBS which will deliver lasting benefits to local communities. We will provide more information around the package as it is developed.
DBS will be a major investment for the local area and wider region, and we will ensure that investment establishes a valuable and lasting legacy for local communities. For example, the maintenance port and facilities will be located on the east coast of the UK in the locality of the DBS site and we plan for all direct labour to come from people living within the area.