Loch Treig Tunnel

Location type


Name and dates

Loch Treig Tunnel (1929-)

Opened on the Loch Treig Deviation (London and North Eastern Railway).


This is a single track and single bore tunnel of 450 ft on the east side of Loch Treig which passes under the west slope of Creagan Faraidh. It is close to, and to the south of, the closed Fersit Halt. It is built on a deviation from the original route, which was just to the west and at a lower level.

The tunnel was created in 1929 when Loch Treig became a reservoir for the Lochaber Smelter and its level was raised. The Loch Treig Dam is 2/3 of a mile to the north. A portion of the trackbed had to be raised above the new high water level of the loch. 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. The original route did not require a tunnel.

Also known as Fersit Tunnel.


Tunnel diversion deviation Loch Treig


Fersit Tunnel

Nearby stations
Fersit Halt
Roy Bridge
Spean Bridge
Invergloy Platform
Banavie Pier
Fort William
Fort William [1st]
Loch Treig Signal Box
Loch Treig Base Camp
Loch Treig Valve Shafts
Loch Treig Speeder Shed
Loch Treig Dam
Bridge 1
Fersit Speeder Shed
Bridge 2
Fersit Siding
Fersit Fitting Shop
Fersit Store
Fersit Cement Shed
Intake C
Bridge 3
Stob Coire Sgriodain
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 Loch Treig Dam and Loch Treig Tunnel were 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.


07/08/1932West Highland Railway
Loch Treig Tunnel and diversion opened. The line was re-aligned at a higher level as the Loch became a reservoir, part of the Lochaber Aluminium Works scheme.