Unit Superheaters Engineering, Swansea

Oxford Archaeology undertook a field evaluation at the Unit Superheaters Engineering Works, Swansea on behalf of Unit Holdings Ltd and DFWJ Ltd. Two trenches were excavated revealing substantial standing structures relating to the historical use of the site and large volumes of dumped deposits that progressively raised the ground level. Significant quantities of kiln and pottery waste debris were recorded at depth in Trench 1 and, along with standing stone walls recorded within Trench 3, are likely to represent the preservation of the Cambrian Pottery works that occupied the site in the late 18th century - mid 19th century. Structural remains relating to the subsequent late 19th-century Patent Fuel works and later use of the site were encountered within Trench 1 cut into the upper levels
of made ground but, significantly, these had not disturbed or truncated the remains of the pottery works. A photographic record undertaken in 1965 of the riverbank reclamation and historical North Dock Basin infilling, alongside the present assessment and recording of the current upstanding historical remains, demonstrate that the river wall, quays and docks all remain substantially intact within the site boundary. The dwarf stone wall at the eastern end of the northern factory unit also predates the current building and appears to originate as a boundary fronting the river side.
2008 phase
Oxford Archaeology (OA) undertook a field evaluation and watching brief
at the former Unit Superheaters Engineering site, commissioned by
Waterman (consultants) on behalf of DFWJ Ltd and Unit Holdings
(clients). Two evaluation trenches were excavated within the northern
part of the site and encountered primary made ground reclamation levels
comprising sand and gravel at 3 m below the modern surface level. These
was overlain by a relatively thin sequence of black silt layers that
contained abundant pottery production waste in the form of unfinished
and broken pottery vessels and various elements and forms of kiln
furniture. The assemblage dated to between 1830 and 1880 although a
small amount of late 18th-century pottery was also present. The pottery
debris represents a significant finding although the extent of these
deposits was not established beyond the evaluation trenches. These
deposits remain undisturbed in situ. No structures that could be clearly
related to these deposits were encountered and the focus of the Cambrian
Pottery works lies within the southern half of the site. These deposits
probably represent the dumping of waste beyond the boundary of the
works. Within the southern area several firebrick structures were
recorded in this phase of investigation adding to the previous evaluation
and watching brief evidence. Combined, these suggest that significant
structural remains are present that could relate directly to the pottery
works.
A series of well preserved stone pillars arranged in a grid pattern
also encountered across the southern part of the site relate to the
Graigola Merthyr Patent Fuel works and can be seen on a contemporary
watercolour view of Swansea from 1881. Alongside the Patent Fuel works
significant contemporary remains were recorded of the North Dock Basin,
canal basin and wharf. These were only exposed at intervals although,
combined with a 1940s view photo of workmen infilling these, it is clear
that they are likely to survive in very good condition. Likewise, the photo
shows that the Patent Fuel Works was levelled and has probably acted as
an effective protective covering to any earlier deposits and structures
buried at depth.
Remains of Villier’s Dry Dock were less well preserved although
the entrance to this was located with the wooden lock gate preserved in
situ. Much of the interior dock structure had been significantly damaged
or removed. However, north of this a series of contemporary walls were
present surviving to a height of 0.7 m built above the pottery-rich layers.
These sandstone walls represent the Cambrian factory located here on the
late 19th century maps. No floor levels or associated deposits were
present.
The detailed watching brief and guidance provided by the
attending archaeologists to the demolition contractors proved to be a very
successful means of removing the modern obstructions without damaging
the earlier structures in the process. Potentially significant structures
were revealed immediately below and around the foundations of the
former Unit Superheaters building foundations. Without the
communicative approach and early involvement strategy adopted, it is
likely that many of these important remains would have been removed as
hard obstacles before their significance was realised.