Orkney-Caithness HVAC 220kV Landfall

Project Location:

Orkney

Client Name:

Scottish & Southern Electricity Networks Transmission (SSENT)

Project Description:

OCU Group delivered two 1,200m parallel landfall crossings as part of SSEN’s 220MW high-voltage transmission project linking Finstown in Orkney to Dounreay in Caithness. The works involved the design and installation of twin 630mm SDR11 PE carrier pipes using Horizontal Directional Drilling (HDD) and pipe-pushing techniques to enable the subsea connection to the national grid.

Completed under a single mobilisation, the operation used casing pipes to stabilise shallow deposits and maintain fluid returns. This project marks the UK’s longest forwardreaming pipe-push installation of its kind - achieved in a remote, coastal location with logistical and geological complexity.

Key Stats:

• Two parallel 1,200m landfall crossings

• Linking mainland Scotland to Orkney Islands

• 630mm SDR11 PE carrier pipes

• Subsea and onshore HVAC transmission system (220kV)

• UK’s longest forward-reaming pipe-push installation

6 Months

Duration

Challenge

• Complexities due to the remote Orkney and Caithness landfall sites, requiring precise planning and coordination

• Tight material delivery schedules required efficient supply chain management

• Extremely hard rock formations and fault zones created difficult drilling conditions

• Pushing HDD pipe over 1,200m presented technical challenges in maintaining bore stability and alignment

• Limited space for HDPE welding and handling required careful onsite planning to maintain safety and quality

Solution

• Early engagement and strong preparation with local Orkney suppliers ensured smooth delivery

• Custom tooling engineered to manage site-specific geology

• Skilled HDD operatives executed the long-distance bores with accuracy and control

• High-volume fluid management (up to 1,000 gallons per minute) maintained bore cleanliness and cuttings transport

• All works delivered under a single, carefully planned mobilisation for maximum efficiency

Outcome

• Project delivered successfully and to programme

• Strong working relationships established with local suppliers and stakeholders

• Effective 24/7 local support throughout the project duration

• Safe and high-quality installation achieved in complex and constrained site conditions

• Set a UK benchmark for forward-reaming, pipe-push HDD installations over 1,200m