Cable Burial Risk Assessment

The Moray West Offshore Wind Farm is a massive undertaking poised to play a crucial role in Scotland's renewable energy future. 

Situated in the Outer Moray Firth, the project encompasses 60 large 14.7 MW turbines over an impressive 225 square kilometres and boasts the potential to generate up 882 MW of clean electricity. 

The project represents a significant investment in Scotland's clean energy future. It is estimated to create thousands of jobs during construction and operation while also providing a significant economic boost to the region. When operational, Moray West is expected to power over one million homes, substantially contributing to the UK's net zero goals.

Moray West is being developed by Ocean Winds (OW), an international company dedicated to offshore wind energy and created as a 50-50 joint venture, owned by EDP Renewables and ENGIE. The OW portfolio for operating, contracted and sites with grid connection rights already encompasses around 18 GW.

Ternan Energy’s involvement

Based out of our HQ in Aberdeen, Ternan were able to provide locally based expertise further supporting growth of the offshore wind sector in Scotland, utilising our local skills and expertise.  This knowledge has been developed through supporting multiple offshore energy projects and it allowed us to help reduce project costs through optimising the use and placement of rock armouring.

Ternan Energy was engaged to provide ongoing Cable Burial Risk Assessment (CBRA) support for the Moray West Offshore Windfarm. The scope of work covered the provision of cable burial risk assessments for the entire wind farm and ongoing support during trenching operations.

The CBRA support covered inter-connector cables, inter-array cables, and export route cables.

Preliminary assessment and data appraisal

The project began with a preliminary assessment of the wind farm's interconnector (IC) cable. The first requirement was to assess the collected data and identify what additional data was required in preparation for the CBRA.

Moray West Offshore Windfarm Layout with Bathymetry

Mitigating risk with a zoning approach

The next stage was the preliminary inter-array cables (IAC) CBRA. This was done before the final cable routes had been confirmed. In such a scenario, we adopt a zoning approach to the site as opposed to profiling the individual routes. This allows for flexibility when routes needed to be modified at a later stage. It also enables data gaps and high-risk areas to be identified.

During this phase, the team identified a unique hazard at the site, surface soil creep, and so we were able to make recommendations to the Moray team regarding the risk this posed to their cables.

Assessing natural and man-made hazards

We then looked at the export cable route (ECR) CBRA. Here, route-specific data was available. The cable route was zoned specifically to account for varying geotechnical/geological conditions and anthropogenic hazards (e.g. shipping lanes). 

By this stage in the project, the team had additional data to work with. Both the IAC and IC CBRA’s were undertaken again with more detailed data. This enabled specific areas considered higher risk to be identified clearly to the client, and the burial depths specified to reflect this.

Export Cable Route Vessel Crossing Density

In-the-moment trenching operations support

Ternan also provided support during the trenching operations on-site and in real-time. This was focused on delivering a “live” assessment of the risk to the cable as first-pass trenching was being undertaken. 

Due to varying soil conditions and vessel activity, sections of the route had different burial requirements. Ternan analysed the burial depth achieved based on residual risk to the cable and were able to make recommendations as to what sections would benefit from a second pass or remedial rock armouring, and which sections this would achieve a negligible reduction in risk. 

Our trenching operations support resulted in reduction of time on site leading to financial savings for the client and also ensured a more targeted rock placement campaign, minimising the required rock along the route.

Export Cable Route As-laid Data

A successful partnership

With the project complete, the feedback from the Moray team has been highly positive.

"Throughout the project Ternan has been easy to work with, responsive and helpful, and were a key deliver partner for the project. We will certainly be approaching Ternan again for future projects." Neil Crawford, Subsea Cables Package Manager, Ocean Winds

For Ternan Energy, this has been a long-term and multi-disciplined engagement.

"It has been great to support Ocean Winds on Moray West which is such a high-profile project. I am delighted to see the team here stepping up to the challenge and providing not just the expert knowledge but also the necessary soft skills to integrate with our clients' team to deliver a successful outcome." Mark Finch, Managing Director, Ternan Energy