In 2021, Brownline was involved in three parallel drillings in north-west Scotland. It proved to be an interesting and challenging project, but the accuracy of our Drillguide GST got the job done in the end.
O’Connor Utilities Ltd was contracted by Scottish and Southern Electricity Networks Distribution to complete three crossings under Loch Linnhe, near its narrowest point at Corran. These crossings were part of a large upgrade project by the power distribution operator, to enhance and improve the reliability of power supplies in the western peninsula of Ardnamurchan. This involved rationalising the onshore network, replacing overhead lines with underground cables. At the Corran Narrows channel, three new power cables were installed under Loch Linnhe.
Laying the cables through underground ducts using a horizontal directional drilling (HDD) method rather than laying the cable on the bed of the loch minimises disruption and helps to improve the long term security of supply. This was of particular importance to the Corran ferry, an essential connection across the loch.
The 465 m / 1526 ft long bores passed through very hard rock formations and loose gravel layers, which complicated the drilling process and hampered a quick progression of the drill and casing. Passing under the loch, it was important that the annular pressure be constantly monitored. The three exit points also required high accuracy, being located on a small strip of land between the shore and a road leading alongside the loch. For such a challenging project, Brownline’s Drillguide Gyro Steering Tool was called in.
In the end, these crossings were completed with the highest accuracy thanks to our GST and the expertise of our HDD specialists. Disruption to the local community on either side of the loch and on the loch itself was kept to a minimum. With the updated cable connection, residents of the Ardnamurchan peninsula will be able to rely on a strengthened electricity network.