Deploying a suite of geophysical probes in an exploratory tunnel over 1km long some 700m below ground level, in boreholes oriented near horizontal and vertical (up and down), was particularly challenging, requiring the development of new equipment and techniques.
The Coire Glas PHS project is located on Loch Lochy in the Scottish Highlands and is scheduled to be operational by 2031, making it the first large scale PHS scheme to be built in the UK for 40 years. When completed the project will deliver a power output of up to 1,500MW with a storage capacity of 30GWh, enough storage to power over 3 million homes for 24 hours.
Coire Glas will utilise Loch Lochy as the lower reservoir and a new upper reservoir, situated in a corrie, or hollow, will be constructed standing more than 500m above the Loch. The upper reservoir will require the construction of a new dam 92 meters in height, largely hidden from ground-level view, retaining the natural beauty of the historic Great Glen area. The tunnels and shafts for the water movement around the scheme and the powerhouse for pumping and electricity generation will be located underground, again minimising environmental concerns.
The project is being led by developer SSE Renewables. Construction company STRABAG UK, with their vast experience in engineering and tunnelling, was contracted to carry out the exploratory works, with Züblin conducting the drilling programme. The exploratory works were designed by SSE Renewables’ consultants, Stantec and COWI.
Robertson Geo Services’ remit was to collect geophysical data in a range of underground boreholes, using a large suite of probes.
An exploratory tunnel was constructed, over 1km in length, in which three galleries were constructed from which a series of long near horizontal and angled boreholes were drilled. For these boreholes, a comprehensive suite of probes was run. In addition, many short “televiewer” boreholes were also drilled and logged for borehole imaging and in situ deformability and stress testing, with some of the boreholes being drilled upwards …click for more
