Exploratory ground works are under way at the site of the £500 million Cruachan power station expansion in Arygll.
The project dubbed “Hollow Mountain” is expected to create up to 1,000 jobs when completed.
The Cruachan 2 expansion will see the construction of an underground pumped storage hydropower plant adjacent to the existing Cruachan facility.
Renewable energy developer, Drax Group, said it will boost the site’s total generation capacity to 1.04GW.
It will also be the first newly constructed plant of its kind in the UK in more than four decades.
The project, on the slopes of Ben Cruachan, near Oban, is expected to commence operations in 2030.
‘Milestone moment’
Drax announced 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.
The plant will be housed within a new, hollowed-out cavern which would be large enough to fit Big Ben on its side, while more than two million tons of rock will need to be excavated to create the cavern, tunnels and other parts of the power station.
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.”
Cruachan Power Station expansion to support jobs and boost economy
Drax submitted the planning application for the Cruachan Power Station expansion in May 2022. It secured development approval from the Scottish Government in July 2023.
Mr Marshall said: “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 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.”
History of Cruachan
Sir Edward McColl, a Dumbarton-born engineer and pioneer of hydro power in Scotland came up with the idea for Cruachan Power Station in the 1930s with wartime Secretary of State for Scotland, Tom Johnston advocating it in 1947.
During the six years of construction, there was a workforce of 1,300 men known as the Tunnel Tigers.
Cruachan Power Station was opened by the Queen on October 15, 1965 with full capacity reached in 1967.