Located on open exposed moorland on the edge of the Yorkshire Dales, this was for CAN Structures a remote project. Not to mention a far cry from the city centres that we often work in. Built by the Victorians in 1870, the tunnel shafts provide ventilation to Risehill Railway Tunnel.
Over time calcite deposits in the original drainage system to these two shafts had stopped them working. This meant groundwater was pouring through the linings and down onto the track level some 45m below. This was then causing the localised flooding to the ballast causing Network Rail ongoing problems with track alignment. In winter large icicles were also forming and would drop off onto the track and even trains below!
The main project requirements
The main project requirement was to replace and also add additional drainage measures into the shafts. This ensured that any water was captured and taken away into the newly installed track level drainage system that ran alongside the tracks in the cess.
The tunnels themselves are both around 45m deep and lie directly over the rail tracks below. In order to keep the lines open to rail traffic through the project, CAN designed bespoke crash decking systems using a lattice work of wires attached to 1m long dowels drilled into the surrounding rock. This was then overlaid with layers of architectural polystyrene blocks to act as energy absorbers. This was installed during track possessions. Once in place, the main works could be completed whilst trains ran underneath. Although, it then meant that the working in the shafts was now a designated confined space. Using rig for rescue techniques alongside the necessary confined spaces equipment meant that CAN was able to safely access and work.
Firstly the old and blocked ring dams were removed, from then, new dams were installed along with lengths of twin wall pipe meaning that all the runoff from the walls would be collected and moved down into the cess drainage system below. Additionally brickwork repairs were undertaken in the upper reaches of the shafts where both the bricks and mortar had perished over the years. Finally new lids were fabricated and installed over the tops of the shafts.
Overall, whilst this was one of CAN’s more challenging projects coupled with a significant number of design changes as a result limited information prior to starting the works it was a success. Even with the changes and additional works, CAN completed the project on time and within budget!
Duration: 12 weeks
Client: Story Contracting