This is a single track and single bore tunnel of 450 ft on the east side of Loch Treig close to, and to the south of, the closed Fersit halt.
The tunnel was created in 1929 when Loch Treig became a reservoir for the Lochaber Smelter and its level was raised. A portion of the trackbed had to be raised to avoid being flooded. The disused section of the line is usually covered by water. At low water the portion alongside the tunnel is well preserved: a stone shelf cut out of a hillside.
Also known as Fersit Tunnel.
Fort William [1st]
| Loch Treigside|
Allt Coire Mheadhoin Viaduct
Stob Coire Sgriodain
Stob Coire Sgriodain South Peak
Stob a'Choire Mheadhoin
Stob Coire Easain
Cille Choirille Church
|Location names in dark blue are on the same original line.|
A Base Camp
During the construction of the West Highland Railway one of the 'base camps' was at the north end of Loch Treig, a location close to where the later tunnel was built.
From this camp supplies were ferried by small flat bottomed 'puffer' to the lochside locations where work proceeded. The line, going south, was slowly climbing to the summit at Corrour Summit, locations further south needing aerial ropeways to reach the works area from the lochside - by the south end of the loch the line was 450 ft above the water level.