SSE – Corran Narrows

OCU has undertaken several high-profile projects in the past 12 months, putting a spotlight on its extensive expertise and ability to adapt to operational challenges quickly. 

In 2022, OCU completed The Corran Narrows project – an underground power cabling project underneath Loch Linnhe in the Scottish Highlands for Scottish and Southern Energy.

The £3.4 million project included the installation of three cables through the process of Horizontal Directional Drilling – drilling 15m through highly changeable geological materials to lay cables underneath bedrock.

From the start, the group needed to overcome several operational challenges, many involving problem solving where no previous solutions existed. When the project had initially begun, drilling through metamorphic Psammite rock – some of the world’s hardest rock and stone – put significant strain on valuable drilling equipment.

With no existing methods of best practice, OCU and its engineers undertook a period of research and development to assess how best to approach the problem. By utilising the hardiness of their equipment at lower speeds they were able to guarantee progress without impinging on operational timelines promised to the client.

The approach to unfamiliar territory highlights OCU’s operational capability and the critical-thinking skills of their engineers to adapt to changeable environments.

As the project continued, the drills encountered areas of glacial till, where large sediment rocks caused occasional jams. To avoid delays, engineers developed a modular percussive drill mole to aid the team. This allowed the equipment to remain stable on the marshland while making it easier to remove when no longer needed, eliminating the need for additional employees to be on site unnecessarily. 

Thanks to OCU, a safe, environmentally benign, and cheaper alternative to the 70km route around the sea loch was successfully implemented. Its completion has also provided a more secure power-supply to residents, affording them the opportunity to decarbonise heating while supporting the Government’s Net Zero ambitions. 

The natural beauty of the surrounding area has also been conserved. With the cables being underground, there is no longer a need for traditional above ground cable and pylons, which would obstruct sightlines and panoramic views over the land.