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Subterranea Scotia

Culligran Power Station - Draft Tube Gallery

Culligran Power Station sign

There is a draft tube access gallery, off the right-hand side of the access tunnel as you descend. The purpose is to give access to the stoplog gates which can be closed to enable the turbines and draft tubes to be dewatered.

Although the tailrace at Culligran is free-flowing (i.e. there is always airspace above the water in the tailrace; it's not a pressure tunnel) the possibility exists that the station could flood through the draft tube gallery if the water level in the river was very high, and there was a backsurge. That's why it's closed with a watertight bulkhead door.

Photo: Culligran - looking into the draft tube gallery from the access tunnel - note how steep the access tunnel slope is.
Photo by: Mike Ross

Photo: the first part of the draft tube gallery ends at a short shaft. Doorway on right leads to toilet
Photo by: Mike Ross

Photo: draft tube gallery continues at the top of the shaft, towards the watertight door.
Photo by: Mike Ross

Photo: Looking back down the shaft
Photo by: Mike Ross

Photo: through the watertight door, looking down into tailrace tunnel.
Stoplog guide rails are visible stoplog gates have been lowered as main unit was under overhaul at this time.
Photo by: Mike Ross

Photo: A ladder descends to the lower level of the stoplog gallery in the previous photo.
Descending that ladder give the view above - from that level one can look straight down the tailrace tunnel to daylight.
Photo by: Mike Ross

Photo: looking back from stoplog gallery through watertight door towards head of shaft.
Photo by: Mike Ross

Finally one from the archives. Looking back down the tailrace at the completed draft tube/stoplog area. The floor of the main level of the gallery is just visible at the very crown of the arch. The lower level (rom where the above picture looking down the tailrace was taken) is the next level down. Everything below this is normally under water. The stoplog gates are in the closed position, so you can't see the outlets of the draft tubes. Two big gates on the right for the main 22MW machine, one small gate on the left for the 2MW compensation set.
Photo by: NOSHEB archives.

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Last updated 13th November 2005
Style © 1998-2001 Subterranea Britannica
Words and images © 2002 Michael J. Ross.