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The Lochaber hydroelectric scheme is a power generation project constructed in the western Scottish Highlands after the First World War. It was intended to provide electricity for aluminium production in Fort William.The scheme was initially designed by engineer Charles Meik but after his death in 1923, the scheme’s realisation was left to William Halcrow, by then a partner in the firm originally founded by Meik’s father Thomas Meik.

The project was finally sanctioned by Parliament in 1921, but construction did not start until 1924; the aluminium smelter was established in 1929 and took about 95% of the 82,000 kW of power generated.

The scheme harnesses the headwaters of the Rivers Treig and Spean and the floodwaters of the River Spey (plus a further eleven burns along the way). The Laggan Dam (213 m long and 55 m high) contained the flow of the Spean in a reservoir (Loch Laggan). A 4 km tunnel then linked this body of water with another reservoir (Loch Treig) contained by the Treig dam. From here, the main tunnel, until 1970 the longest water-carrying tunnel in the world, an enormous 24km long and 5m in diameter, was driven around the Ben Nevis massif. From the western mountainside, down five massive steel pipes, the water rushes towards the turbines in the power house at the smelting plant.

In 2008 Rio Tinto Alcan announced an investment of £45m to upgrade the plant, including replacing the generators which have been in use since 1929 (!), safeguarding 600 jobs in the area.