Robertson Geo was tasked with carrying out a major data-gathering operation to support development of the Coire Glas pumped storage project in Scotland.
The company was contracted by Strabag UK Ltd to collect detailed geotechnical data for the £1.5 billion scheme, located near Loch Lochy, close to Inverness. Coire Glas will be the UK’s largest pumped storage facility since the Dinorwig Power Station was built in the 1980s. Led by SSE Renewables, the project is expected to deliver up to 1300MW of capacity.
Conwy-based Robertson Geo, which provides borehole geophysical and petrophysical logging services, deployed geophysical probes in an exploratory tunnel more than one kilometre long and 700m underground.
Managing Director Simon Garantini said: “The exploratory work being undertaken for Coire Glas is among the most extensive ground investigations of its time, collecting and analysing a huge volume of geotechnical data before construction begins.”
He added: “The comprehensive scope of the ground investigation is not least required due to the site’s proximity to the Great Glen fault line, which is visible from outer space. The geotechnical data will observe ground conditions to inform on the potential risks and challenges posed to a successful delivery of the project, so this was a hugely important task, pivotal to them moving forward.”
Garantini described the work as “challenging,” noting it involved techniques and equipment the company had not previously used, including a 2,000m winch enclosed in a safety cage.
The tunnel features three galleries with long horizontal and angled boreholes, as well as short boreholes used for imaging, deformability, and stress testing. Operations are running continuously, with two teams of two engineers working 12-hour shifts around the clock.
“The most challenging aspect of the logging operation was the development and deployment of a ‘push’ system to place logging tools in horizontal boreholes,” said Garantini. “Our team has considerable experience in using them on horizontal boreholes up to about 40m in length. However, these were up to around 280m so the magnitude of the task could not be underestimated.”
He continued: “There were other challenges – notably in designing a push system for the raised boreholes up to 22m in length – but a manual arrangement using customised tubular push rods was engineered, which worked successfully.”
Garantini also noted issues such as equipment handling underground and environmental factors like noise and dripping water, which required on-the-spot solutions.
“The geophysical logging campaign we undertook formed a vital component of the overall ground investigation, providing high-quality calibrated data, not attainable by other means, at centimetre resolution in the boreholes,” he said.
Robertson Geo operates in more than 160 countries and runs a global rental service for borehole logging equipment. The data collected at Coire Glas will play a key role in informing the next phase of the project.
