Saltford Tunnel East Portal (MLN11157)

Summary

A tunnel portal in the Tudor-Gothic style, with a four-centred arch, set in an cutting under the village of Saltford in an otherwise a rural landscape. Erected c.1836-40.

Reasons for Designation

Saltford Tunnel East Portal is designated at Grade II for the following principal reasons:
* Date: the portal dates from the Pioneering phase of railway design, prior to 1840, and as such there is a presumption in favour of listing;
* Architectural interest: its Tudor Gothic design by Isambard Kingdom Brunel is of clear architectural interest;
* Historic interest: as a design of circa 1836-40 by Brunel;
* Intactness: the portal is remarkably unaltered and survives well;
* Group value: as part of the most architecturally interesting and imaginative sequence of railway tunnels in the country.

History

Great Western Railway

The Great Western Railway was authorised by an Act of Parliament in 1835 to construct a line from London to Bristol. At 118 miles this was slightly longer than the other major trunk railway of its time, the London and Birmingham (112 miles) and considerably longer than other pioneering lines. Construction of the line began in 1836, using a variety of contractors and some direct labour. The first section to be completed, from London to Maidenhead Riverside (Taplow), opened in 1838, and thereafter openings followed in eight phases culminating in the completion of the whole route in 1841. Work at the Bristol end of the line had started in 1835, and the section from Bristol to Bath had opened in August 1840.

The engineering of the railway was entrusted in 1833 to Isambard Kingdom Brunel (1806-59), who was already known for his engineering projects in Bristol. More than any other railway engineer of his time he took sole responsibility for every aspect of the engineering design, from surveying the line to the detailing of buildings and structures. He sought to achieve as level a route as possible and, working from first principles, he persuaded the Directors of the GWR to adopt a broad gauge of 7ft 0¼ in rather then the standard (4ft 8½in) gauge in use on other lines. A two track broad gauge line was 30ft wide, and this determined the span of the overbridges and other structures. Except for larger bridges such as Maidenhead Bridge, the majority of Brunel’s masonry bridges did not need to be as innovative as his works in timber and iron, and his structures followed the typical architectural idioms of his time, but they were all beautifully detailed and built and together they formed integral parts of a consistently-designed pioneering railway.

Although he left no written statement concerning his design concept for the line, it can be inferred from its design and from the way it was described when opened that part of his vision was a line engineered according to picturesque principles. This influenced his selection of the route and the design of structures along it. For reasons of cost, but also because it helped blend the railway to the landscape, he used local materials for bridges and other structures, ranging from stock brick at the London end of the line, to red brick, Bath stone east of Bath and Pennant stone west of Bath. This intentional variety was remarked on by contemporaries, for instance in J.C. Bourne, 'The History and Description of the Great Western Railway' (1846). On the line from Bristol to Bath, where the track runs along the Avon valley valley, Brunel chose to use Tudor four-centred arches for both the over- and underbridges, and castellation for tunnel portals and viaducts. This makes it the most distinctive part of the whole route from London to Bristol, and it is also the section on which the structures have generally survived in their original form because this part of the route was not quadrupled and the Pennant stone used for most structures has lasted well.

Existing contract drawings for bridges and other structures on the Bath-Bristol section of the line carry the signature of I.K. Brunel, reflecting his involvement with every aspect of the project. The Resident Engineer was G.E. Frere (1807-87), assisted by G.T. Clark (1809-98) and Michael Lane (1802-68), but their individual contributions have not been identified.

Saltford Tunnel

Saltford Tunnel is a very short tunnel (160m) lined in Pennant stone, with a horseshoe-section, bored directly under the village of Saltford west of Bath. It was one of twelve tunnels designed and constructed by Brunel between Chippenham and Bristol. Saltford Tunnel East Portal was built c.1836-40 under contract 3B. The original contract drawings survive, together Brunel's original sketch designs in his sketchbooks. There have been no major works to the portal since construction.

As executed, the West Portal (MLN1 11164) resembles the East.

Details

MATERIALS: ashlar Bath stone portal and copings. Square and coursed Pennant stone retaining walls and tunnel lining. Small engineering brick patches.

DESCRIPTION: depressed, four-centred arch, with a span of 30ft (9m), consisting of ashlar voussoirs and a recessed roll and then hollow moulding. No stops to these mouldings are visible (though they are shown on the contract drawings; they may be buried beneath ballast). Two small sections of engineering brick patching. The arch is set within a giant square hoodmould with stops, which frames chamfered spandrel panels. This ashlar portal is itself set within a coursed Pennant stone retaining wall extending above and to the sides. This is topped by a plain coping course which rises gently to a peak over the centre. A low coursed rubble retaining wall abuts the south (Down) side. This has a segmental-arched niche with basin, which may be the outlet for a natural spring. It is not shown on the surviving contract drawings.

The tunnel is not very deep, and buildings and gardens of the village of Saltford crowd the low hill above the portal.


This list entry was subject to a Minor Amendment on 18/07/2012

Sources

Books and journals
Brindle, S, Cruickshank, D, Brunel: The Man Who Built the World, (2005)
Bourne, J C, The History and Description of the Great Western Railway, (1846)
Cross-Rudkin, P, Chrimes, M, EDS, Biographical Dictionary of Civil Engineers Volume 2: 1830–1890, (2008)
MacDermot, E T, A History of the Great Western Railway, (1927, revised ed. 1964)
Pugsley, A, The Works of Isambard Kingdom Brunel, (1976)
Maggs, C, The GWR Bristol to Bath Line , (2001)

Other
Alan Baxter & Associates, The History and Significance of the Great Western Main Line , 2012,
Kinchin-Smith, R, Crossrail Technical Assessment of Historic Railway Bridges , 2005,
Brunel, I, K , Sketchbooks, Brunel Institute and the University of Bristol,
Network Rail, National Records Centre Roll Number 13117, 13119, 13123 and 13128a,

End of official list entry

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