Ffestiniog Railway: relict sections south of Tanygrisiau

Cadw's description

Summary description and reason for designation

The monument comprises the relict remains of the Ffestiniog Railway where it navigates the eastern slopes of the Moelwyn mountain range south of Tanygrisiau. Two early routes of the Ffestiniog Railway survive between Llyn Tanygrisiau and Dduallt Station. The earlier of the two routes follows the western shore of the lake to the South of Ffestiniog Power Station and then the public footpath over the ridge to the south of Llyn Tanygisiau. The later route follows a course to the east - the north of the formation is within the lake, the central section comprises a tunnel through the ridge and a substantial causeway survives to the south. Both routes meet east of Gelliwenog where a contour formation extends for a further 450m to meet Dduallt Station.

The Ffestiniog Railway Company was founded in 1832 and is the oldest independent railway company in the world. The 2’ gauge railway was developed between 1832 and 1836 to carry slate product from the quarries of Ffestiniog to Porthmadog for international export. The railway was surveyed by the engineer James Spooner and was designed as a gravity and horse-drawn system, laid out using a near constant gradient of 1/80. Steam locomotives were introduced in 1863 by which time every major quarry of the Ffestiniog region had a connection to the railway.

The gravity system is evident at Llyn Tanygrisiau but the constant gradient of the railway is interrupted by the ridge that connects Moel Dduallt and Moel Ystradau. When the railway opened in 1836 a temporary expedient of an up-haulage inclined plane was introduced on the northern side of the ridge and a counter-balance incline on the southern slope to carry wagons over the col. This system was powered by waterwheel, fed by a reservoir formed by the damming up of Afon Ystradau. The massive earth-core dam, faced with roughly coursed rubblestone and buttressed on the north side is named Archer’s Dam after the first managing director of the Ffestiniog Railway Company. The dam survives today in two parts having been breached by the modern railway in 1971 to allow the Ffestiniog Railway deviation to pass through. The uphaulage incline survives as an earthwork with rubblestone facing stones forming a partial revetment, while only the lower part of the southern incline survives along the line of the modern public footpath.

A tunnel 668m in length was cut in 1842 making the incline system redundant. The old Moelwyn tunnel, also designed by Spooner, was last used in 1957 and was plugged by the Central Electricity Generating Board during the construction of the Llyn Ystradau pumped storage scheme, known as Ffestiniog Power Station. The railway formation is visible through the clear water of the lake and the northern tunnel portal can be seen when the lake is low. The only above ground evidence of the tunnel is the three ventilation shafts and their associated spoil tips which mark the line of the tunnel as it passes through the ridge. At the southern end of the tunnel a second stone portal survives before the railway is carried across a shallow valley to meet the 1836 route using a substantial rubblestone causeway. This impressive causeway survives today at 138m in length and more than 6m in height on the eastern elevation.

A contour section of the relict railway continues for a further 450m to the south to Dduallt Station where the formation meets the deviation that carries the modern heritage railway. This section retains significant archaeological potential with well-preserved in-situ rails evident. An overbridge that provided access to Gelliwenog farm survives in an adjacent field having been dislodged and partly dismantled. The bridge is constructed from old rail sections, with concrete over an iron plate deck and side rails of iron bars fastened to rail sections. The steep eastern approach ramp built of rubble-stone and slate slabs, is largely undisturbed, and still has the old rail stanchions which once supported guard rails or wires. The southern extent of the relict 1836 railway survives as a short length of stone-faced embankment c.1m high, partly cut into the bedrock and partly flanked by a low rubble-stone wall. At the southern end some sleepers survive in situ while others have been dislodged during historic salvage.

The monument is of national importance for its potential to enhance our understanding of the slate quarrying industry, specifically the evolution of transport systems and transport engineering. It is one of a small number of elements of the Ffestiniog Railway to survive in a relict state and includes a number of monumental structures. It retains significant archaeological potential and may be expected to contain archaeological information concerning function, chronology and phasing.

The scheduled area comprises the remains described and an area around them within which related evidence may be expected to survive. The scheduled area includes the 1836 route which is c.2km in length and c.5m in width, orientated N-S between NGR 267885, 344245 – 267885, 342225 with a short break between NGR 267790, 343000 – 267845, 342895. To the west of the 1836 route Archer’s Dam comprises two discrete polygons c.30m E-W by c.10m transversely at NGR 267620, 343350 and NGR 267665, 343340. To the east of the 1836 route the 1842 tunnel is primarily an underground feature between NGR 267800, 343515 – 267945, 342865 but retains 3 air shafts with associated spoil tips above ground at NGR 267840, 343340, NGR 267895, 343135 and NGR 267910, 343025.