Geotechnical challenges and measurement programme in the exploration tunnel for the Coire Glas pumped storage power plant

Abstract SSE Renewables is one of the UK's leading renewable energy developers and plans to build the first pumped storage power plant in over 40 years with the Coire Glas project. The fully underground facility at Loch Lochy in the Scottish Highlands will have a capacity of 1300 MW and a storage capacity of 30 GWh, which will more than double the UK's current storage resources. In preparation, geotechnical investigations began in 2022 under the name “Coire Glas Exploratory Works”. STRABAG UK Ltd was awarded the contract following a public tender and work began in November 2022. A major part of the project was the construction of an initial 0.9 km long exploratory tunnel, the length of which was extended to 1.2 km during the course of the work. The aim of the investigations was to record the geological and hydrological conditions in order to safeguard the planning of underground structures such as pressure shafts, turbine and transformer caverns and access tunnels.