Pencader Tunnel

It is approximately 988 yards (903 m) long (just over half-a-mile), making it the longest tunnel in West Wales and is bored through Ordovician shales.

[1] From the first proposals of the Carmarthen and Cardigan railway it was known that an expensive and long tunnel would be needed to take the line between the valleys of Skanda Vale (in which Llanpumpsaint station resided) and Dolgran, under the Brechfa Forest watershed.

Brunel proposed a dead-straight tunnel to connect the valleys, though after reworking, the final design was longer in order to ease the gradients.

Construction started in the spring of 1857 to bore the tunnel at the same time as work began on the first stage of the railway line in the town of Carmarthen.

Once the second shaft was finished, digging also commenced from there, though this had been abandoned by May 1860 according to a report which stated that 576 yards (527 m) had been dug by this time, approximately two-thirds of the full length.

During construction of the tunnel, many of the horses used to haul away excavated rock died from disease and were buried in the field surrounding the northern of the two shafts.