Summary
A culvert designed by I.K. Brunel and constructed c.1839, with a Blue Lias stone horseshoe arch. Set in an embankment between Keynsham Hams Underbridge (MLN111404, Grade II) and Durley Lane Underbridge (MLN111439, Grade II).
Reasons for Designation
Stream Culvert, Keynsham, 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;
* Rarity: a rare example of a culvert or underbridge to survive intact from the earliest phase of the Great Western Railway;
* Design: an architectural treatment on structures of this type is unusual and, in this case, the voussoirs, wing walls and coping add to the special interest;
* 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 Blue Lias 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 Blue Lias stone used for most structures has lasted well.
Existing contract drawings for bridges and other structures on this 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.
Stream Culvert, Keynsham
The culvert near Keynsham was constructed under Contract 2B and was built as shown in the relevant contract drawing. The culverts on the line between Bath and Bristol are classically derived (e.g. with voussoirs) although more substantial structures on this stretch were designed in a Tudor-Gothic idiom. This part of the line opened in August 1840. Minor additions have been made to the area immediately around the south portal in the C20.
Details
MATERIALS: squared and coursed Blue Lias stone.
DESCRIPTION: an 8ft (2.4m) span horseshoe arch (length c.113ft) (34m), made of squared and coursed stone. Both elevations have voussoirs, plain coping and no parapet. There are small wing walls that are convex in plan and sweep down in elevation. These abut the arch at its base. The soffit is coursed stone. Modern, round-section, galvanised steel handrails are mounted on the coping. On the south (Down) side, a coursed rubble retaining wall is attached to the west (high mileage) wing wall, angled south along the course of the stream. A slab of concrete has been cast beneath the arch against the east (low mileage) wing wall.
