Groundbreaking seismic surveys underway for new ‘Hollow Mountain’ power station

Exploratory ground works at the site of what would be the UK’s first pumped storage scheme to be developed in 40 years are underway on the slopes of Ben Cruachan, near Oban in Scotland.

Renewable energy leader Drax is progressing plans to build a new 600 MW underground plant adjacent to its existing Cruachan facility. Seismic surveys are being taken to provide crucial geological data about the rock in which the new plant would be housed inside. The process involves drilling holes into the rock and laying small explosive charges which are detonated to produce a powerful sound wave within the rock mass.

It is expected that the sound wave will penetrate up to 60m below the ground surface before its reflected signal fades away. Sensitive equipment called geophones mounted on the ground measure the progress of the sound waves to provide information about fractures, fissures, or potential weak spots in the rock.

Pumped storage hydro plants act like giant water batteries, using reversible turbines to pump water from a lower reservoir to an upper reservoir which stores excess power from wind farms and other low carbon technologies when supply outstrips demand. These same turbines are then reversed to bring the stored water back through the plant to generate power when it is needed.

Steve Marshall, Development Manager, said: “The expansion of Cruachan will be one of the most significant engineering projects in Scotland for many decades. The start of these seismic surveys of the mountain is a real milestone moment for the project and everyone at Drax is excited to see the development take another step forward, These surveys will further complement borehole drilling works undertaken in 2022 and 2023 at the site.

“With the project granted development consent from the Scottish Government, we hope the next UK Government will continue policy development in this area at pace to enable a new generation of pumped storage plants to come online as soon as possible.

“Expanding Cruachan will strengthen the UK’s energy security by enabling more homegrown renewable electricity to come online to power homes and businesses across the country. This major infrastructure project will support hundreds of jobs and provide a real boost to the Scottish economy.”

Increasing the country’s pumped storage hydro capacity is critical to enabling more renewable power to come online, strengthening the country’s energy security whilst helping the UK to decarbonise.


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