Rhondda Tunnel: Site Investigation

Engineered by S. W. Yockney, the Rhondda Tunnel is the longest disused tunnel in Wales at 3.1km. Today the portals are buried and the tunnel has been closed for more than forty years. Construction was carried out from both ends, taking five years to bore from June 1885 to 2nd July 1890. It features a single 58-foot ventilation shaft around 105 yards from its western end and is almost 300m below ground at its deepest point. A remarkable feat for the time and all with no prior site investigation.

Underground springs ensured that the Rhondda Tunnel was very wet in places; this was channelled away via a drainage system. Coal working caused the lining to bulge and a series of reinforcement ribs was erected in 1938. Eleven years later, an inspection found the tunnel to be in excellent condition except for two sections where distortion was severe.

The tunnel was closed in 1968 temporarily while funds were being found to repair it, but instead the British Railways board decided to close the whole line.

The Rhondda Tunnel Society hopes to raise enough money to reopen the tunnel as a cycle path. In September 2017 it was announced that the Society had been awarded a grant from the Vattenfall Pen y Cymoedd Wind Farm Community Fund. This grant would allow three surveys to be undertaken:

  1. A survey into the defects of the tunnel with estimates on how much it would take to fix them.
  2. A geotechnical survey looking at the materials used to seal both ends of the tunnel.
  3. A survey of the land which is marked to receive the excavated material. It is hoped this can be used to level ground and create space for camping, car parking and a visitors’ centre.

ESP are proud to be working with the Rhondda Tunnel Society implementing a Geotechnical Site Investigation and Survey around the Blaencwm and Blaengwynfi Portals of the Rhondda Railway Tunnel and providing general geotechnical and geo-environmental support to the project.


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