The hydro-electric station at the plant took large volumes of water from the River Foyers from an intake just above the falls, significantly reducing their flow.

The plant was built without the need for Parliamentary approval, because the company bought the Lower Foyers estate, through which the river ran, and they were thus able to ignore the public outcry at the spoiling of an amenity.

This became the upper reservoir for a pumped-storage hydro-electric scheme when the newly closed works was taken over by the North of Scotland Hydro Electric Board.

The falls influenced Robert Addams, a travelling lecturer in natural philosophy, to write a paper in 1834 about the motion aftereffect.

The most promising was the Heroult-Hall process, separately developed by P T L Heroult in France and C M Hall in America in 1886-1887, but it required large amounts of electricity.

This allowed them to create a hydro-electric scheme without needing to obtain Parliamentary approval, and to ignore public opposition to the effects it would have on local amenities.

The River Foyers ran through a gorge to the almost vertical Lower Falls, which was a beauty spot, and was a stopping point for tourists using the MacBrayne pleasure steamers running along the Caledonian Canal from Fort William to Inverness.

From there a tunnel was cut through solid rock for 0.5 miles (0.80 km) and the water continued through cast iron pipes to the generating station.

The water drove five Girard turbines connected to Oerlikon direct current generators, which could produce a total of 3.75 MW.

By that time Fulton had been succeeded by K R Vernon, an engineer with wide experience, that included working on the construction of another pumped storage scheme at Cruachan.

Like Cruachan, the system would be a hybrid, where about 25 percent of its output would be derived from water flowing from the catchment into Loch Ness, and the remainder would be from the pumped storage element.

This was at Tom an Eig, and by following a curved route, the low pressure tunnel could be driven through Foyers granite from Loch Mhòr to the surge shaft.

However, the route was bisected by the Gleann Liath, a small lower lying valley, and because the quality of rock was so poor, the pipeline ran off the surface for a short distance.

[14] Edmund Nuttall Ltd won the contract for the surge shaft, the high pressure tunnels, the power house and lower control works.

The contract for the low pressure tunnel was awarded to Duncan Logan Construction, but they went bankrupt after six months on site, and Nuttall's took over this part of the project as well.

[16] The new power station is situated on the east bank of Loch Ness, to the north of the aluminium smelter, and was formally opened in April 1975.

From the surge chamber, the water fills a vertical concrete shaft which is 367 feet (112 m) deep and the same diameter as the low pressure tunnel.

Engineers from Kvaerner Markham of Sheffield, England cut away the damaged steelwork and fitted redesigned linings, which had to be welded in situ, before 400 anchor bolts were used to attach them to the concrete.