Colne Valley Viaduct
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Colne Valley Viaduct | |
|---|---|
 Viaduct in January 2025 over Korda Lake | |
| Coordinates | 51°35′09″N 0°29′24″W / 51.5859°N 0.4900°W |
| Carries | High Speed 2 |
| Crosses | Colne Valley Regional Park |
| Locale | |
| Characteristics | |
| Total length | 3.38 kilometres (2.10 mi) |
| Width | 14.3 metres (47 ft) |
| Height | c.10 metres (33 ft)[1] |
| Longest span | 80 metres (260 ft) |
| No. of spans | 57 |
| Piers in water | 11 |
| Rail characteristics | |
| No. of tracks | 2 |
| Track gauge | 1,435 mm (4 ft 8+1⁄2 in) |
| Electrified | 25 kV 50 Hz AC |
| History | |
| Architect |
|
| Engineering design by | Rendel-Ingerop, Jacobs |
| Constructed by | Align JV (Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick) |
| Construction start | March 2021 |
| Construction end |
|
| Statistics | |
| Daily traffic | High speed passenger trains |
| Location | |
 Interactive map of Colne Valley Viaduct | |
The Colne Valley Viaduct is a railway bridge that will carry High Speed 2 over the Colne Valley Regional Park and the Grand Union Canal. It runs between Harefield in Hillingdon, Greater London and Denham in Buckinghamshire. At a length of 3.38 km (2.10 miles) and a weight of 116,000 tonnes, it is the longest railway bridge in the UK. It is one of the largest single civil engineering works of High Speed 2. Trains will travel at about 320 km/h (200 miles per hour) on the bridge.
A contract for the section of the railway pertaining to the viaduct was awarded during 2017 and the design concept was shown in January 2018. Preparatory work commenced shortly thereafter, including a compulsory land purchase and the establishment of temporary facilities, including a factory, onsite. Construction of the viaduct began in March 2021, with the main deck completed in September 2024 and full completion of the bridge in September 2025. Protestors occasionally occupied the site, and allegations over the viaduct's aesthetic and environmental impact upon the area have been made.
The Colne Valley Viaduct was intended to be a major civil engineering work of High Speed 2, being amongst the largest and perhaps the most prominent single feature to be constructed on the project.[1][2] Its basic configuration is a gently-curved structure along a horizontal radius of 5,280 m (17,320 ft), supported by 57 spans, with 11 V-shaped piers in water, and weighing roughly 116,000 tonnes in total.[3] The viaduct crosses over both the River Colne and the Grand Union Canal, at which points its spans are spaced at intervals of 80 m (260 ft); the majority of over-land spans cover shorter lengths of either 45 or 60 m (148 or 197 ft).[4][1] Trains will travel at about 320 km/h (200 miles per hour) on the bridge.[5]
Considerable attention has been directed to the viaduct's aesthetic design and to avoid unnecessarily impacting the surrounding landscape and local community.[1] To reduce its impact upon wildlife and the general public alike, four-metre (13 ft) high transparent acoustic barriers were installed along the entire length of the viaduct; these will reduce noise emissions while only incurring a minimal impact upon the view of onboard passengers.[4] The design of the overhead electrification equipment was also bespoke to reduce its visual impact. The exterior concrete surfaces are faceted to provide a more attractive visual and tactile design.[1] However, the viaduct has been subject to criticism from Stop HS2 for allegedly ignoring the needs of local residents.[6] Rail industry periodical Rail Engineer notes that the site of the viaduct features multiple factors of sensitivity, pertaining to both environmental and public interests, as well as access issues during the construction phase.[1]
The main deck of the viaduct was manufactured at a nearby temporary factory, the assembly of which was commenced from the northern end.[1][7] In total, 908 deck units and 92 pier head units were produced; weighing between 60 and 140 tonnes, each one unique to its intended place in the overall structure. Assembly used a match-casting technique with relatively tight tolerances, supported by an adjustable steel formwork and prefabricated steel reinforcement where relevant.[1] While two deck units were to be typically cast each day, the more complex pier head units required three days to complete. To appropriately handle rail braking loads of up to 9,000 tonnes, a total of four shock absorber units were integrated into the deck structure of the viaduct.[1] The structure also features four expansion joints. The foundations consist of driven piles upon which the faceted framework is installed; water-based piers are considerably more complex in shape and design.[1]
In November 2024, the viaduct won the Royal Fine Art Commission Trust's annual Building Beauty award in the engineering category. The judges praised it as a “tour de force that despite its scale [...] treads lightly, skimming over the water”, noting especially its elegant expansion joints, varied concrete treatments and lightweight acoustic wings.[8][9] The Times called the bridge "a two-mile-long masterpiece".[10]
