Hydro Scheme

The major Affric-Beauly scheme commenced with Constructional Scheme No. 7, The Mullardoch – Fasnakyle – Affric Project.  The scheme uses water collected from a catchment area of 124 square miles around Glen Affric & Glen Cannich. Prior to the establishment of the Hydro, plans by the Grampian Electric Company to produce electricity in this area were rejected by Parliament in 1929 and 1941. These schemes proposed to raise Loch Beinn a’ Mheadhoin to the same level as Loch Affric thus creating a single body of water and submerging many of the scenic features of Glen Affric. Fortunately, this outcome was deemed unacceptable.

The revised project saw a relatively small dam constructed at the outflow of Loch Beinn a’ Mheadhoin, moderately raising the level of the loch by just 23 feet. Lost storage here and in Loch Affric was replaced by the building of a mass gravity type dam at the outlet of Loch Mullardoch in Glen Cannich. This is a much grander construction measuring some 2385ft in length and 160ft tall at its highest point. In the construction 286,000 cubic yards of concrete were used to retain a mass of 7.5 million cubic feet of water. The water level of Loch Mullardoch was thus raised by 113 feet. The two Lochs are interconnected by a tunnel just over 3.5 miles long driven through the mountainside having a fall of around three feet over its entire length. This difference in level allows an underground generating station at the Mullardoch end of the tunnel to further increase output (2.4MW).

From Loch Beinn Mheadhoin another tunnel system comprising a long low-pressure section linked by a high-pressure shaft to a high-pressure tunnel. This last section having a gradient of 1 in 50, leads to the power station at Fasnakyle. A short distance from its end the high-pressure tunnel splits into three smaller tunnels that initially fed three vertical Francis turbo-alternators, each capable of producing 23MW of power. In 2006 work on a fourth (underground) generator was completed during a major extension to the station.

The tunnelling work was completed under extremely difficult and dangerous conditions by a hardy breed of men of many nationalities dubbed “Tunnel Tigers.” Numerous British and European records for removing rock were broken by the Tigers. Wages for those employed on the Hydro schemes were high for the time and hardly surprising the tunnellers were among the top earners.