Building the last Main Line Railway

Catesby Tunnel and Viaduct: gcrcs189

View of the 'Survey Station' erected by the contractor above Catesby tunnel to aid its construction. The survey station would have been built in a location and at height that would maximise its line of sight. Because the tunnel was nearly 3000 yards long there would have been several of these structures over the top and in line with the path of the tunnel beneath. They would have incorporated both a bench mark, for calculating height which would be required for ensuring the tunnel's horizontal accuracy, a datum point for ensuring correct alignment along its length. The reason for their being was because the bore was driven from at least 8 intermediate shafts and from both ends of the tunnel. Each intermediate point would see the bore be driven in two directions thus at least 18 faces would be in operation reducing the construction time significantly. On the right of the picture, a line of well laid contractor's railway leads towards the headgear and temporary structures surrounding shaft No 7.

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