More and more damaged cables are costing time and money, says Consub

Guest article by Consub

At CONSUB, we are seeing reports of more and more poorly executed subsea crossings.  Several recent and ongoing projects have suffered significant time delays and the associated cost implications from damage caused to third party infrastructure.  It’s not only the immediate vessel time required to survey and investigate the damage, but the additional engineering and rectification works, not to mention the significant knock-on effect to project schedules and budget.

Douglas Hall, Survey Manager, CONSUB, says: “While concerns around security and vulnerability to attack - particularly from so-called “bad actors” - grab the headlines, the reality is that deliberate interference with subsea cables remains relatively rare.  However prudent it may be to consider such risks, in practice, there’s statistically a greater risk that damage arises from planned installation of subsea infrastructure, and this must be addressed.”

Seabed becoming increasingly congested

As Europe accelerates its transition to renewable energy, the seabed is becoming increasingly congested. Offshore wind farms, interconnectors, pipelines, and existing communications cables are creating dense networks of assets that must coexist within limited corridors. Each crossing point represents a potential vulnerability, and it must be properly designed and executed.

Our analysis of recent projects has highlighted multiple root causes, these include:

- errors in crossing design

- lack of reliable survey data

- poor installation methodologies

- poor procedure execution 

- misunderstanding of ground conditions.

To counter these causes, there must be well-engineered crossings, supported by clear agreements between asset owners, and this must happen to ensure long-term integrity and operational reliability. This makes crossing design not just a technical consideration, but a critical element of project risk management.

Crossing agreements define responsibilities, installation methodologies, protection measures, and future access rights. They require careful negotiation and a deep understanding of both engineering constraints and operational realities. Similarly, the physical design of a crossing, whether through rock placement, concrete mattresses, or separation structures, must account for ground and environmental conditions, load interactions, and lifecycle considerations.

As offshore development continues at pace, particularly in support of Europe’s energy transition, knowing how to structure a robust crossing agreement and deliver a reliable crossing design is essential. This is an area where CONSUB brings deep expertise, with a proven track record across complex offshore projects.

Douglas Hall concludes: “As the seabed becomes more crowded, we have seen the repercussions of poorly executed subsea crossings. The only way that projects can proceed with confidence, minimise risk and safeguard critical infrastructure, is with well-engineered subsea crossings, with clear agreements between asset owners. The alternative will only mean further increased costs and time delays.”