Pwll Du Tunnel

Cadw's description

Summary description and reason for designation

The monument consists of the remains of the Pwll Du tunnel which carried Hill’s Tramroad from Blaenavon Ironworks through the mountain to Pwll Du (MM224). The tunnel (Item A) originated as a mining level, driven into the hillside above Blaenavon to extract coal for use in the iron furnaces. Around 1815 the level was extended to create a tunnel between Blaenavon and Pwll Du and a tramroad laid through it which was used to move limestone from the Pwll Du and Tyla quarries to the Ironworks. At just over 2000m in length it was the longest tunnel on any horse-drawn tramroad in Britain. The tunnel was a significant feature of the operations of the Blaenavon Company until the 1850s when it was superseded by Dyne Steel’s Incline (MM280). It originally had a single entrance at each end (Items B & C), with the tramroad exiting the northern end of the tunnel adjacent to Lower Rank in Pwll Du village. In the 1840s a second entrance was created at Pwll Du (Item D) on the eastern side of the village adjacent to Tunnel House, possibly to make movement easier between the tunnel and Pwll Du Quarry and Garnddyrys forge. In the late nineteenth century static steam engines were installed to replace the horse-drawn waggons, and an engine house built at each end of the tunnel. The tunnel continued in use until the 1920s, later being abandoned and the entrances bricked up. At the Blaenavon end of the tunnel are the remains of the engine house and possible stables (Item E) adjacent to the entrance, as well as the footings of Tunnel Houses, early nineteenth century Blaenavon Company housing and their associated gardens (Item F).

The monument is of national importance for its potential to enhance our knowledge of the development of industrial transportation in the 18th and 19th centuries. The tunnel, tunnel entrances, track bed, drainage systems, embankments, revetments and other associated structures may all be expected to contain archaeological information in regard to construction techniques and functional detail. It retains significant archaeological potential, with a strong probability of the presence of intact archaeological features and deposits. The site forms part of a larger cluster of monuments related to the industrial workings of the Blaenavon Company, including Pwll Du Limestone Quarry and Water Balance Lift (MM225), Garnddyrys Ironworks (site of) and Adjacent Tramway (MM189), Pwll Du Village (MM224) and Blaenavon Ironworks (MM200), and their importance is further enhanced by their group value.

Originally scheduled in 1994 as ‘Pwll Du Tramroad Tunnel Southern Approach’, this scheduling has been revised to include the full extent of the Pwll Du tunnel and the northern entrances, which were originally scheduled as part of MM224. The scheduled area comprises the remains described above and an area around within which related evidence may be expected to survive. It is irregular in plan, 2240m in length, around 70m in width at each end and 11m wide along the length of the tunnel and is centred on OS NGR SO 24799 10724.

Archaeological Items
Item A – Pwll Du Tunnel
The Pwll Du tunnel is c. 2km long, passing between the remains of Pwll Du village to the north and Blaenavon to the south. The tunnel rises in height approximately 21m between the southern and northern portals, it was rock cut along most of its length, driven through the Garw and Farn coal seams, with wooden pit props used to support the roof. At each of the entrances, the tunnel consists of short sections of arched stonework, recorded as 25m in length at the Garnddyrys entrance. At Pwll Du the original tunnel entrance lay immediately adjacent to the eastern end of the houses on Lower Rank, with the tramroad splitting to go west to Tyla Quarry and east to Pwll Du Quarry and Garnddyrys. At a later date, probably in the 1840s, a second entrance was added on the eastern side of Pwll Du village and a Y-shaped junction created in the tunnel around 90m from the Tyla entrance. The tunnel contained a tramroad on a 2-ft gauge, set on sleeper stones, and in the later years of use battery operated bell wires were installed to allow communication between each end. Coal Authority maps indicate the presence of extensive workings into the coal seams around the tunnel, which was evidently used to facilitate access. The tunnel was also used by residents of Pwll Du as a short cut to Blaenavon. There have been several roof collapses within the tunnel which was blocked in the twentieth century and is not accessible.

Item B – Blaenavon Entrance
The entrance at the Blaenavon end of the tunnel was reconstructed in 2010 using reclaimed house bricks and is currently in a poor state of repair. Archaeological investigations undertaken at the time of the reconstruction identified the in-situ tunnel portal to have been constructed from refractory bricks pointed in black lime mortar which abutted the stone arched tunnel. The mortar suggests that this is a later addition to the structure, late nineteenth/early twentieth century in date, and evidently replaced the original portal.

Item C – Tyla Entrance
The Tyla entrance is located adjacent to houses at Lower Rank in the former village of Pwll Du (MM224). The entrance was open until 1989 when it was sealed by the Coal Authority. The stone portal has elements of the original structure in it but has been reconstructed, and the brick wall with gate are modern.

Item D – Garnddyrys Entrance
The Garnddyrys entrance is located adjacent to Tunnel House in the former village of Pwll Du. It is largely buried with only the top 0.5m of the stone arched tunnel and blocking wall visible beneath the turf.

Item E – Engine House and possible Stables
Mapping evidence shows the presence of four structures at the mouth of the southern entrance to the tunnel. The largest of these is similar in size to the engine house at Pwll Du and may be the location of the steam engine at the Blaenavon end of the tunnel. The remaining buildings are smaller and may have been stables for the horses. The remains of two of these structures can still be seen on the ground, with one building immediately adjacent to the tramroad south of the tunnel surviving as low footings with a 1.5m high stone wall on the western side of the building. The structure is overgrown and has stone and soil partly covering it, but intact structural remains are likely to be preserved beneath the later deposits. Above this structure is a terrace on which the footings of the larger building can be identified below the turf. Any traces of the other buildings are obscured by vegetation and later episodes of tipping.

Item F – Tunnel Houses
Tunnel Houses comprise a pair of Blaenavon Company cottages dating to the early nineteenth century, located above and to the west of the tunnel entrance. They were accessed along a track leading from the south and had a yard with outbuildings immediately in front of them and small gardens and fields. The remains of the buildings are overgrown and difficult to access but consist of piles of rubble covering walls that survive to around 1m in height. The remains of some outbuildings can be traced within the old yard, and the form of the track and small fields to the south can be seen through aerial images, although they are overgrown with vegetation.