Press Release October 2004

Helicopters used to transport Drill rig to site

A proposal by Scottish and Southern Energy (SSE) to build the UK's first, large-scale hydro-electric scheme for 40 years, mainly underground, is currently before the Scottish Executive. A dam and aqueduct on a 600m-high plateau will be linked to an underground generation facility close to the shores of Loch Ness by a 4.5 metre diameter tunnel. Once in operation, it is expected that the scheme will produce up to 100MW. SSE awarded Fugro Engineering Services Ltd (FES) the 10-week site investigation carried out in the summer of 2004.

Longyear 38 rigs and a Fraste tracked mini-rig were transported by helicopter to the proposed dam location high above Loch Ness where FES engineers drilled approximately 50 shallow boreholes to check the depth of peat and till plus nine deeper boreholes, from 30 to 50 metres, along the proposed dam and aqueduct alignment.

Drilling on the remote site 600m above sea level

To investigate the tunnel, vertical and inclined boreholes drilled to 350m deep were required - several times the depth of a typical civil engineering project. Drilling rigs needed to be set up on in woodland and open moorland with access along rough, hillside tracks. Here, FES used three Unimog-mounted Knebel rotary rigs to drill vertical and inclined boreholes to depths of up to 350 metres using coring and open hole techniques. Geophysical borehole logging, with optical and acoustic televiewers, natural gamma and calliper logging techniques, was carried out in each borehole.

Hydraulic fracturing was performed within the tunnel zone to determine the in-situ stress at the depths of interest in selected boreholes. These specialist operations were performed by Solexperts AG and the Norwegian Geotechnical Institute at depths of between 220 and 280 metres. Following processing of the results, the stress magnitude was shown to generally increase in depth and be consistent across the site.

Inclined boreholes drilled with a Knebel rig

Laboratory rock testing was successfully completed at FES's Soil Laboratories in Consett plus specialist laboratories in Norway and the UK