River Arkaig

This particular project is part of a wide range of projects currently being constructed in the north of Scotland, with the aim of securing future energy resources for the UK by developing renewable energy. The project harvests an endless supply of nature’s resources, creating an output of electricity for the UK, before returning natures resources unaffected by the project.

The site is located within a remote highland estate, approximately 15miles north of Fort William, which is littered with rivers and lochs of varying sizes. The river in which the hydro scheme is being constructed upon is up-to 40m wide in places and fed by a loch exceeding 13miles long.

In its past use, the brownfield site had been used by the estates owners as a series of mills and small workshops, which also had a small hydro turbine mounted upon a pipeline from the mill pond to the river in the 1970’s.

Work consisted of site clearance works including the demolition of the older dis-used buildings, prior to a large scale excavation through the rock strata to allow the construction of the much more efficient and much larger hydro turbines. Approximately 3000T of rock had been required to be broken out with depths reaching 5.5m.

The structure required to house the 21m long hydro screws was constructed using in-situ concrete walls, which were anchored into the rock strata below. The concrete channel itself was 40m long, with a 60m long tailrace constructed to reduce velocities of water prior to it re-entering the watercourse at the outlet. To ensure that the flow of water through the turbines, a 40m long pre-cast concrete weir was constructed on the upstream of the hydro scheme to divert water into the turbines, whilst maintaining a flow of water down the natural river channel to ensure that the local wildlife was not affected by the project. A 60m long concrete fish pass was also built to the side of the hydro turbines to allow safe passage of fish past the works.

This particular project required quite a certain degree of care and consideration in relation to wildlife. Working closely with SEPA and ecologists, many species including fish, otters, bats, nesting birds and deer were protected throughout the works. Environmental controls and techniques such as stilling ponds, sedimentation bags, silt fencing, electrofishing, licensed bat removal/re-housing, concrete washout areas and substance controls were used. The environment was also protected throughout the works with tree protection zones implemented to preserve natural habitats.