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Glenlee Power Station and Tunnel
Glenlee, Dumfries & Galloway, Scotland, UK
associated engineer
Sir Alexander Gibb & Partners
Merz & McLellan
date  1931 - 1935, 2010
era  Modern  |  category  Power Generation  |  reference  NX605805
ICE reference number  HEW 1457/09
Glenlee Power Station is the control centre for the Galloway Hydro-Electric Project, which has a catchment area of 103,600ha in south west Scotland. It is supplied with water from Clatteringshaws Loch to the south west, via a tunnel and pipeline with a combined length of 6.3km.
Water isn't drawn off at the dam but from the eastern side of the reservoir 2.4km to the north (NX551777) where it is conveyed into a circular reinforced concrete intake tower or shaft. This is 30m tall and has an external above-ground diameter of 5.2m. Below ground, its walls are concreted directly onto the excavated rock face. The base of the tower connects with the tunnel through a bellmouth opening.
The concrete-lined tunnel is 5.8km long and has a flattened circle cross-section of 3.35m equivalent diameter. It is constructed on a gradient of 1 in 350 over most of its length, with the final kilometre on a gradient of 1 in 100. At about its midpoint the tunnel passes under Craigshinnie Burn, which is intercepted at a weir and its water let into the tunnel through one of the vertical driving shafts adapted for the purpose.
The tunnel was the most expensive and challenging part of the Galloway project. It was driven through rock, largely by blasting with gelignite, with battery-powered locomotives used for removing the arisings. Excavation was completed in about 18 months, followed by application of the concrete lining.
A 7.3m diameter surge shaft on the tunnel is situated some 210m from the downstream portal at Glenlee. It was sunk vertically from above and intercepts the tunnel some 43m down. During a surge, water overflows the shaft into a small holding reservoir. A large chamber 32m long and about 7.3m high was constructed near the bottom of the shaft, containing enough water to keep the tunnel full of water if full load is activated at the power station.
A 488m long flange-bolted single steel pipeline, weighing 640 tonnes, joins the tunnel portal to the power station. The tunnel is connected to the pipeline by a 3m diameter butterfly valve inside a concrete valve house (NX602802), which controls the flowrate. The pipeline decreases from 2.9m to 2.5m in diameter and ends in a bifurcation at the station. From there two pipes of 1.8m diameter carry water to the twin 12MW turbines. Water leaving the turbines flows through an 823m tailrace into the River Ken.
Each of the main turbines is connected to an alternator generating a three-phase current of 11kV. There are also two 560kW auxiliary turbines. Power is stepped up to 132kV for transmission to the UK's National Grid.
The power station has a maximum output capacity of 24MW for an average net head of 116m of water, which can be generated within five minutes. It was commissioned in March 1935 and is housed in a building of symmetrical Modernist design, constructed in reinforced concrete.
Since the 1970s, the whole Galloway scheme has been controlled from Glenlee Power Station. Individual generators are operated in proportion to customer demand and available water.
The power station building was Category B listed in April 1990.
The inside of Glenlee’s penstock was cleaned and repainted for the first time in 2010, using high-pressure water jets to remove old paint, debris and mill scale. The bare metal was then sprayed with two coats of glass flake epoxy paint. Work was completed between February and October.
Contractor: A.M. Carmichael Ltd
Steel pipework: Sir William Arrol & Co Ltd
Generating machinery and switch gear: English Electric Co Ltd
Valves, gates and sluices: Glenfield & Kennedy Ltd
Penstock refurbishment (2010): N.E.T. Waterjet Ltd, Meigle
Penstock refurbishment (2010): Concrete Repairs Ltd
Research: ECPK
"Galloway Hydro-Electric Scheme" information leaflet available at www.scottishpower.com
"Galloway Hydros" series of factsheets available at www.spenergywholesale.com
reference sources   CEH SLB

Glenlee Power Station and Tunnel