Summary
A road underbridge in the Tudor-Gothic style with a four-centred arch, set in a low embankment. Erected c.1839-40.
Reasons for Designation
The Avon Mill Lane Bridge, constructed c.1839-40, is designated at Grade II for the following principal reasons:
* Date: an early example of a railway structure dating from the pioneering phase in national railway development;
* Architectural interest: it is characteristically well designed, by the hand of Brunel, with a moulded four-centred arch flanked by stepped buttresses, moulded string courses and parapets terminating in piers, in a Tudor-Gothic style;
* Group value: it forms part of a group of architecturally similar overbridges on the section between Bristol and Bath;
* Historic association: it is constructed to a design by Isambard Kingdom Brunel who is widely perceived as one of the most important transport engineers and architects of the C19.
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, 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 Bristol-Bath 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.
Avon Mill Lane Bridge
Avon Mill Lane Bridge was one of the structures built c.1839-40 in time for the opening of this stretch of the line in August 1840. Contract drawings survive together with a sketch in one of Brunel's sketch books show him trying five different variations for Gothic underbridges and selecting the design which was executed as a variant at Avon Mill Lane. The bridge is largely unaltered
Details
MATERIALS: pennant stone throughout, squared and coursed on the faces and soffit, ashlar dressings for voussoirs, quoins, string course and copings.
DESCRIPTION: depressed, four-centred arch of 16ft (5m) span with a simple chamfered profile terminating at the footings in chamfer stops. Low continuous chamfered plinth around the external faces and the carriageway faces. Soffit and carriageway faces unaltered throughout. On both sides, the archway flanked by buttresses, whose coped caps support a plain string course running across the face. Plain parapet above with chamfered coping. Faces continue beyond buttresses as straight wing walls, terminating in piers. On the south (Down) side, a course rubble retaining wall alongside the roadway abuts the buttress west of the arch at right angles, and another lower retaining wall does the same against the east buttress on the north (Up) side. Late C20 steel tubular steel railings attached to the north (Up) parapet and the metal plates fixed to the arch ring highlighting the low headroom are not of special interest.
This list entry was subject to a Minor Amendment on 19/07/2012
