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Black Road causeway, Black Bridge and World War II reservoir at Copperhouse Pool

A Scheduled Monument in Hayle, Cornwall

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Latitude: 50.193 / 50°11'34"N

Longitude: -5.4107 / 5°24'38"W

OS Eastings: 156662.759711

OS Northings: 38125.985223

OS Grid: SW566381

Mapcode National: GBR FX05.JDH

Mapcode Global: VH12N.5DGV

Entry Name: Black Road causeway, Black Bridge and World War II reservoir at Copperhouse Pool

Scheduled Date: 25 August 2001

Last Amended: 17 December 2010

Source: Historic England

Source ID: 1020400

English Heritage Legacy ID: 15564

County: Cornwall

Civil Parish: Hayle

Built-Up Area: Hayle

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Phillack

Church of England Diocese: Truro


The monument includes an early 19th century causeway, called the Black Road,
across the upper end of Copperhouse Pool, the broad, shallow eastern arm of
the Hayle estuary in west Cornwall. Near the centre of the causeway, the Black
Bridge carries the causeway over the tidal channel of the Copperhouse Creek.
The monument also includes a World War II reservoir impounded against the
north east side of the Black Bridge. The Black Bridge is a Listed Building
Grade II.
The `Black' element in the name of both the causeway and bridge (also known as
Sea Lane and Sea Lane Bridge respectively) derives from their facing of
rectangular, moulded blocks of very dark, glassy, copper-smelting slag called
scoria. Scoria blocks were a by-product from the Cornwall Copper Company's
smelter which operated from 1758 to 1819 at Copperhouse, south of Copperhouse
Pool. Produced in large quantities, scoria blocks were used extensively for a
variety of building purposes during the smelter's operation and for long after
it ceased production, providing one of the distinctive architectural features
of the area.
The Black Road causeway is visible for 197m north west-south east, crossing
Copperhouse Pool from an area of raised ground on the south east to the sea
wall fronting the north of the Pool. The causeway is up to 17.5m wide at its
base, rising up to about 2m high to a flattened upper surface about 10m-11m
wide. Within that upper surface the carriageway is now visible as a 4.5m wide
gravelled track, but earlier records note its former metalling by scoria
waste. The south west side of the causeway is faced by coursed scoria blocks,
largely unmortared except for the upper course near the bridge. The scoria
facing has a steep slope, called a batter, and rises at least seven courses
high beside Black Bridge. The causeway's upstream facing, on the north east
side, is almost entirely obscured by accumulated silts and overlying
vegetation. At intervals along the causeway, roughly-worked upright granite
guide-slabs, variously 0.6m to 1.16m high, stand in pairs, one to each side of
the present track, marking the road when the causeway was inundated at high
spring tides. Two pairs of such guide-slabs, 37m apart, survive north west of
Black Bridge; to the south east of the bridge, only one guide-slab now
survives, 50m from the bridge on the south west verge.
The Black Bridge is situated south east of the causeway's midpoint and
measures 19.3m long overall with a carriageway 4.65m wide. The bridge spans
the channel of Copperhouse Creek by two unequal rounded arches separated by a
single pier lacking cutwaters. The south eastern arch, 4.75m wide, is lower
and wider than the north western, 4.35m wide. This asymmetry reflects an early
modification reputedly to allow the boat of the Rector of Phillack to pass
beneath the bridge. The abutments also differ: on the south east, the sides of
the bridge extend about 2m from the arch before splaying out to the sides of
the causeway while the north western abutment splays from close beside the
springing of the arch. The faces of the bridge rise from the arches, pier and
abutments to flank the carriageway as a parapet up to 1.2m high and 0.5m wide,
level over the main body of the bridge but angled down above the abutment
splays. The downstream side parapet over the north west abutment follows a
course inside that of the abutment, leaving a step on top of the abutment
The bridge is faced almost entirely by coursed rectangular scoria blocks,
mortared except at lower levels, with scoria blocks also providing the
arch-rings and paving across the channels beneath the arches. Limited use of
brickwork infills the irregular shapes where blockwork courses approach the
curves of the arch-rings. The parapet coping is also of scoria blocks but
these are edge-set and moulded to a pointed arch in profile. The carriageway
between the parapets now has a rough gravelled surface which breaks over the
north western arch to reveal the outer surface face of the scoria block
The Black Road and Black Bridge were built during the first two decades of the
19th century to provide more direct access from the Cornwall Copper Company
works at Copperhouse to the company's main quay facilities at North Quay; the
year 1811 is considered the most likely date of construction, when the company
obtained the freehold of North Quay.
During World War II, a reservoir north east of Black Bridge was used to store
water for emergency fire-fighting purposes, enlarging an earlier, smaller pool
formed by sluice gates inserted against the upstream side of the bridge by
1908; similar but earlier sluices may have produced ponding behind the bridge
apparent on maps of the 1830s and 1840s. The 1940's reservoir is retained by a
small dam immediately behind the bridge's north east face. The dam comprises
three large shuttered-concrete blocks, 0.6m thick and 1.6m high, separated by
two sluice gate gaps, 1.6m wide and 1m deep, narrowing to slender gaps between
the blocks' bases. The reservoir, now partly silted, extends 25m north east
from the bridge by up to 24m wide, north west-south east, and about 1m deep. A
raised bank diverts the upstream channel of Copperhouse Creek around the north
east of the reservoir, only merging with the reservoir close behind the
All modern electricity poles, fittings and cables, all street lighting
equipment, and the modern gravel metalling of the track are excluded from the
scheduling, although the ground beneath these features is included.

The site of the monument is shown on the attached map extract.
It includes a 2 metre boundary around the archaeological features,
considered to be essential for the monument's support and preservation.

Source: Historic England

Reasons for Scheduling

The Hayle Estuary, one of the few natural harbours on the north coast of south
west England, was an important focus for trade and the movement of people and
ideas in the prehistoric and early medieval periods. The area around the
estuary has produced prehistoric artefacts with Irish affinities and, later,
some of the earliest post-Roman evidence for Christianity in south west
England, again showing strong Irish influences. Trade and religious elements
continued with a growth of pilgrimage to European shrines and more locally to
St Michael's Mount, but rapid decline set in during the later medieval period
as the estuary became choked by silts from tin extraction along the valleys
feeding into it. By the early post-medieval period, the estuary was surrounded
by dispersed settlement remote from regional and national centres of trade and
economic power.
This situation changed dramatically from the mid-18th century with the need to
service the increasingly industrialised exploitation of tin and copper in west
Cornwall. The resulting developments show the considerable extent to which
industrialisation restructured earlier economic, settlement and transport
patterns, overcoming significant natural difficulties to meet its needs.
Extensive quays built from 1740 at the heart of the estuary facilitated the
import of coal and other supplies required for the mines. A copper smelter
built by Copperhouse Creek in 1758 further stimulated business on the quays.
The difficult maritime and land access to and within the estuary was eased in
1769 by constructing the Copperhouse Canal and Dock, and, in the early 19th
century, by the Black Road across Copperhouse Creek and by the early
development of the Hayle Railway. Blocks of slag, called scoria, from the
Cornish Copper Company's smelter, provided a distinctive building material in
the rapid growth of the Copperhouse district.
In 1779, Harvey's Foundry was established at the head of Penpol Creek, an area
later known as `Foundry'. Initially serving local mine needs, it became one of
the world's leading suppliers of industrial pumping engines in the early 19th
century, a role shared with the rival Copperhouse Foundry which supplanted the
copper smelter that ceased operation in 1819. In contrast to Copperhouse,
Harvey's drew much of its workforce from nearby villages, tending to build
large villas rather than urban housing on its land. Fierce competition over
access to quays produced the `South Quay' built by Harvey's in 1819,
aggravating the natural problems of estuarine silting. These problems were
resolved by impounding Copperhouse Pool and, from 1834, creating the wholly
artificial Carnsew Pool as tidally-filled sluicing pools whose waters were
directed to the canal, quays and harbour mouth. This complex system maintained
the port facility that gave the foundries their national and international
role besides serving their regional hinterland. Accompanying this industrial
growth, the foundry companies operated as general merchants, developing the
necessary storage, cartage and stabling facilities and further stimulating use
of the port.
From the 1860s, rapid economic decline of the Cornish mining industry
undermined the foundries' core business leading to their closure, at
Copperhouse in 1869 and Harvey's for heavy engineering in 1903. In the early
20th century Hayle diversified into ship-breaking, light engineering and
general cargo shipping, but these also underwent serious decline.
The survival of extensive elements from the early industrial development of
the Hayle Estuary and their contrasting nature in differing areas contributes
much to the distinctive character of Hayle in the present day. These survivals
also have a wider significance from Hayle's role as the world's leading
supplier of pumping engines in the early 19th century, especially for deep
mining, and are of major importance for studies of this formative period of
our present industrialised society.

The Black Road causeway and Black Bridge have been little modified and survive
well. Their physical survival and documented origins demonstrate clearly the
major changes and improvements to the transport infrastructure which the early
industrial development required around the Hayle Estuary. In particular they
form a tangible illustration of the close economic relationship between the
manufacturing sites and the wharfage providing import and export facilities.
The scoria block construction of both the causeway and bridge is highly
unusual, a good example of the diverse applications of this by-product of the
copper smelting industry and part of the distinctive contribution which the
Hayle area makes to the national stock of architectural fabrics.

Source: Historic England


Books and journals
Buck, C, Smith, J R, Hayle Town Survey, (1995)
Buck, C, Smith, J R, Hayle Town Survey, (1995)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
CAU, Cornwall SMR entry PRN 139245,
CAU, Cornwall SMR entry PRN 31974,
DCMS & EH, AM7 & internal core data & reports for CO 987,
DCMS, Listed Building entry SW 5638-5738 9/106,
In conversation on 13/7/2001, Information given in conversation with MPPA, (2001)
In conversation on 13/7/2001, Mr Frank Johns ex Hayle Town Councillor, Information given in conversation with MPPA, (2001)
Title: 1:10000 Ordnance Survey Map SW 53 NE
Source Date: 1979

Title: 1:10000 Ordnance Survey Map: SW 53 NE
Source Date: 1979

Title: 1:2500 Ordnance Survey Map SW 5637-5737
Source Date: 1970

Title: 1:2500 Ordnance Survey Map: SW 5637-5737
Source Date: 1970

Title: 25": 1 mile Ordnance Survey Map Cornwall sheet LXII: 14
Source Date: 1908

Title: Map of Bodriggy Waste with Indenture of land N of old highway
Source Date: 1836
In Cornwall Record Office
Title: Ordnance Survey 25": 1 mile Map Cornwall sheet LXII:14
Source Date: 1877

Title: Ordnance Survey 25": 1 mile Map Cornwall sheet LXII:14
Source Date: 1908

Title: Phillack Parish Tithe Map
Source Date: 1842

Source: Historic England

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