Glenlee Tunnel

NX57NE 37.00 5510 7779 to 6028 8026

NX57NE 37.01 NX 5511 7779 to NX 5520 7789 Inlet tower, inlet and causeway

Causeway [NAT] (at NX 551 778).

OS 1:10,000 map, 1979.

Extends across map sheets and NX68SW.

For surge tower at NX 60120 80124, see NX68SW 68.02.

For associated minor works, see dam (NX57NE 38) at NX 57768 78863 and adit (NX57NE 39) at NX 59492 79454.

For associated Clatteringshaws Loch or Reservoir (centred NX 540 769) and Glenlee Power Station (NX 6060 8055), see NX57NW 41.00 and NX68SW 68.00 respectively.

Glenlee tunnel and intake. The tunnel intake works [NX57NE 37.01] on the Clatteringshaws reservoir [Clatteringshaws Loch: NX57NW 41.00] are situated on that side of the new loch nearest to the Glenlee power station at a point some 1½ miles [2.4km] distant from the dam [NX57NW 41.01]. They are placed at the further end of a rock embankment about 100 yards [91m] in length, leading out from the shore, and consist of a concrete structure to hold removable gates lifted and lowered from an overhead steel gantry and a reinforced concrete valve tower, immediately above the mouth of the tunnel. The lowest draw-off level of the reservoir is 545ft [166m] above OD and the top water or spillway level 585ft [178m] above OD, while the sill level of the intake works is placed 542ft [165m] above OD. From the lip, there is a sharp drop down the shaft to the level 520ft [159m] above OD of the invert of the tunnel. The tunnel is horseshoe-shaped in section, with a greatest diameter of 11ft 6ins [3.7m].

The length of the tunnel is about 19,000ft [5793m] and it is 11ft 6ins [3.5m] in transverse diameter. Work upon its driving was begun in May 1932, and finished by October 1933. It has been built with a gradient of 1 in 350, except for the last 3600ft [1098m] which slopes more steeply at 1 in 100. It was excavated from the two ends, from a shaft [NX57NE 42] at Craigshinnie, and from an adit [NX57NE 39] driven horizontally into the Glenlee hill. It lies in general on a line running from SW to NE. At the Craigshinnie shaft, however, it tales a slight bend towards the N, and subsequently, before reaching the adit, turns more steeply towards the S. These changes of direction were dictated by the necessity to obtain sufficient rock cover. From the adit it turns towards the N again, and is driven straight to the outlet portal. The methods employed for the excavation of the tunnel call for no special mention, but it is worthy of note that when the concreting of the tunnel was begun a gantry of no less than 120ft [36.6m] in length was used on the straight portions. A smaller gantry, 30ft [9.1m] long, was used on the curved portions, and after these were completed this was attached to the main gantry and concreting then proceeded in lengths of 150ft [45.7m] at a time. Concreting was finished by June of this year [1934].

The waters of two streams, the courses of which cross the line of the tunnel, have been diverted down the Craigshinnie shaft. The collection of this water involved the construction of a short length of aqueduct.

About 700ft [213m] from the outlet portal, a surge shaft [NX68SW 68.02] has been driven down from above into the tunnel. It is 24ft [7.3m] in diameter, and is connected with the tunnel by a throat 11ft [3.35m] in diameter, which is carried down 5ft [1.5m] below the invert of the tunnel to form a sump. With its floor about 25ft [7.6m] above the tunnel invert, there has been excavated horizontally from the surge shaft a chamber 105ft [32m] long by 16ft [4.9m] wide, with an average height of about 26ft [7.9m]. This chamber is connected with the shaft by two holes, one above the other, each 10ft [3m] in diameter by 15ft [4.6m] long, the lower of which is situated just at the top of the throat section of the shaft. It provides space for the accommodation of a large quantity of water to be to be drawn on in the case of a heavy downward surge which might be caused by the rapid throwing on of full load on the power station. Its roof is built to a radius of 8ft 6ins [2.6m], and, together with the sides, is lined with concrete, the floor being unlined. For the protection of the turbines in the power station from any material that might be carried out from the surge chamber, the throat portion of the shaft is provided at its upper end with a lip 3ft 3ins [1m] in height. The top of the surge shaft opens on to a hillside, which has been excavated and embanked to create a dry 'pond', which is lined where necessary with concrete. Into this 'pond', water from the tunnel may rise after a heavy surge, subsequently flowing back into the tunnel. The top of the surge shaft, which is concreted throughout, bears a lip 5ft [1.5m], with six openings in its sides protected by gratings for the return flow of the water. Small subsidiary openings at the base of the lip drain a surrounding gutter.

The contractor was A M Carmichael.

Anon. 1934 ['Galloway Water Power Scheme'].

(Illustrations include plan and profile of the tunnel, and photographs of concreting gantry and of completed tunnel lining).

Anon 1934 ('The Galloway Water Power Scheme').

This tunnel forms a major element of stage I of the Galloway Hydro-electric Scheme, taking water from Clatteringshaws Loch reservoir (NX57NW 41.00) north-eastwards to Glenlee Power Station ( ), beneath Glenlee Hill and the grounds of Craigshinnie. This tunnel was the most expensive single element in the scheme.

The line underground is not indicated on current OS maps, but a map published at the time of construction indicates a kinked route from the intake channel (NX 5510 7779) to the SW end of the penstocks (NX68SW 68.01) above the power station. The map notes a shaft, dam and aqueduct to the W of Craigshinnie (NX 5826 7919), and an adit to the E. The dam and adit are presumably those noted as such on the 1979 edition at NX 5775 7885 and NX 5950 7945 respectively.

The tunnel ends (at NX 6028 8026) at the SW end of the penstocks (NX68SW 68.01) above the power station, and there is a surge tower (NX68SW 68.02) at NX 6012 8012, a short distance to the SW.

The area is now afforested, and the entire tunnel lies within the parish of Kells.

Information from RCAHMS (RJCM), 13 October 2005.

Gibb and Partners et al. 1934; G Harrison 1966.