Colne Valley Viaduct

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Colne Valley Viaduct
HS2-VL-10383-CVV Harefield-Lake 190524-3.jpg
Artist's depiction of the completed viaduct
Coordinates51°35′23″N 0°28′47″W / 51.589654°N 0.479687°W / 51.589654; -0.479687Coordinates: 51°35′23″N 0°28′47″W / 51.589654°N 0.479687°W / 51.589654; -0.479687
CarriesHigh Speed 2
CrossesColne Valley Regional Park
LocaleHarefield
Characteristics
Total length2.1 miles (3.4 km)[1]
Height10 metres (33 ft)[1]
Rail characteristics
No. of tracks2
Track gauge1,435 mm (4 ft 8+1⁄2 in)
Statistics
Daily trafficHigh speed passenger trains
Location

The Colne Valley Viaduct is an under construction bridge which will carry the High Speed 2 railway over the Colne Valley Regional Park and the Grand Union Canal, in Hillingdon, west London. Possessing a length of 2.1 miles (3.4 km) and a weight of 116,000 tonnes, it is the largest railway bridge in the UK, as well as one of largest single civil engineering works of Phase 1.[2]

A contract for the section of the railway pertaining to the viaduct was awarded during 2017; the design concept was released to the public on 19 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 commenced during March 2021; the completion of the main deck has been anticipated to occur during 2024. Protestors have occasionally occupied the site, and allegations over the viaduct's aesthetic and environmental impact upon the area have been made.

History[]

Various means for High Speed 2 to traverse the Colne Valley were considered. One option which was studied as an alternative to using a viaduct was the extension of the nearby Northolt tunnel, which was also being built for the new line, however this option was dismissed in a report released in February 2015 due to the increased costs and construction time that would be involved.[3] During 2017, Contract C1 (Central 1), which covers the 21.6km section of the line that the viaduct falls within, was awarded to the Align JV joint venture, comprising Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.[1]

On 19 January 2018, the design concept for the Colne Valley Viaduct, which was created by Knight Architects and Atkins, was unveiled by the British Government.[4][5] This concept was produced in consultation with the Colne Valley Regional Park Panel.[1] Additional work on the viaduct's design has also been undertaken by Grimshaw Architects.[6]

In April 2019, Buckinghamshire County Council requested that the government pause all preparatory work until the Oakervee Review had been completed and disagreed with HS2 Limited over mitigation works.[7] During March 2021, Hillingdon Council and HS2 Limited came to an agreement in which, in light of written assurances from the latter, the former shall not pursue a judicial review into the scheme.[8] Shortly following this decision, full planning permission for the viaduct was secured.[2]

Design[]

The Colne Valley Viaduct is 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 during Phase 1.[1] In terms of its basic configuration, it is a gently curved structure along a horizontal radius of 5,280 metres (17,320 ft), supported by 57 spans and weighing roughly 116,000 tonnes in total. The viaduct crosses over both the River Colne and the Grand Union Canal, at which points its spans are spaced at intervals of 80 metres (260 ft); the majority of over-land spans cover shorter lengths of either 45 or 60 metres (148 or 197 ft).[9][1]

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, 4-metre (13 ft) high translucent acoustic barriers are to be 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.[9] 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 ignoring the needs of local residents.[10] 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 is to be manufactured at a nearby temporary factory, the assembly of which is to commence from the northern end.[1][11] In total, 908 deck units and 92 pier head units will be produced; weighing between 60 and 140 tonnes, each one unique to its intended place in the overall structure. Assembly will use a match-casting technique with relatively tight tolerance, supported by an adjustable steel formwork and prefabricated steel reinforcement where relevant.[1] While two deck units are to be typically cast each day, the more complex pier head units will each require three days to complete. To appropriately handle rail braking loads, a total of four shock absorber units are to be integrated into the deck structure of the viaduct.[1] The structure will also feature four expansion joints. The foundations will consist of driven piles upon which the faceted framework is installed; water-based piers are considerably more complex in shape and design.[1]

Construction[]

As early as 2018, protestors had taken up positions in the Colne Valley to voice their objections to the project.[12] In April 2019, twelve Extinction Rebellion protesters began treesitting in order to prevent HS2 Limited chopping down trees as part of preparatory works at Harvil Road, near to the proposed site of the viaduct.[13] There had been a protest camp next to the road since October 2017, which HS2 began evicting in January 2020.[14]

In order to clear the viaduct's intended path, a farmhouse was compulsory purchased while a watersports centre was required to relocate. Both properties are to be demolished.[15][16] Various preparatory works were also undertaken during the 2010s, including the diversion of water mains, the realignment of 275 kVa overhead power line, and a reinforcement of a gas mains, along with other measures.[1] Towards the northern end of the viaduct, a temporary construction compound has been assembled, which accommodates offices, plant, employee welfare facilities, and the pre-cast factories for the project. Sufficient space for the storage and treatment of up to 3,000,000 cubic metres (110,000,000 cubic feet) of chalk slurry has also been provisioned for the construction of the Chilterns tunnel to the north of the viaduct.[1][17]

During March 2021, construction of the viaduct's foundations commenced, although test piling had occurred before this.[18] Between Spring and Summer 2021, an internal access road was built, while the onsite factory building the viaduct segments were commissioned during the autumn . During Spring 2022, deck construction will commence from the northern embankment; completion of the deck has been anticipated in mid-2024.[1] The first pier for the viaduct was cast in December 2021.[19]

References[]

  1. ^ a b c d e f g h i j k l m n o p q "Colne Valley Viaduct – HS2's largest bridge". railengineer.co.uk. 7 June 2021.
  2. ^ a b Horgan, Rob (1 April 2021). "HS2 secures full planning consent for UK's longest rail bridge after council drops legal challenge". newcivilengineer.com.
  3. ^ "Proposal for Northern Extension of Northolt Tunnel SIFT Report" (PDF). High Speed 2. 27 February 2015. Retrieved 3 July 2020.{{cite web}}: CS1 maint: url-status (link)
  4. ^ "HS2 reveals Colne Valley viaduct concepts". GOV.UK. Retrieved 28 July 2020.
  5. ^ Smale, Katherine (19 January 2018). "HS2 reveals controversial Colne Valley viaduct". newcivilengineer.com.
  6. ^ Hopkirk, Elizabeth; Rogers, Dave (15 April 2020). "Huge boost as government tells HS2 to start work". Building Design. Retrieved 28 July 2020.
  7. ^ Smale, Katherine (6 August 2019). "HS2 and council clash over Colne Valley viaduct 'uncertainty'". New Civil Engineer. Retrieved 29 July 2020.
  8. ^ "Hillingdon and HS2 declare peace over plans for Colne Valley Viaduct". hillingdontimes.co.uk. 19 March 2021.
  9. ^ a b "HS2 Colne Valley Viaduct". Grimshaw. Retrieved 28 July 2020.
  10. ^ Wareham, Stephanie (24 January 2018). "Campaigners criticise HS2 plans for 'one of the longest viaducts in UK'". Bucks Free Press. Retrieved 29 July 2020.
  11. ^ Horgan, Rob (14 June 2021). "The reality of working on HS2's biggest construction site". newcivilengineer.com.
  12. ^ Topham, Gwyn (8 December 2020). "Veteran activist Swampy among protesters in HS2 site standoff with police". theguardian.com.
  13. ^ Snaith, Emma (27 April 2019). "Extinction Rebellion activists camp out in trees to protest HS2". The Independent. Retrieved 29 July 2020.
  14. ^ Taylor, Diane (7 January 2020). "HS2 begins evicting activists from protest site after two years". The Guardian. Archived from the original on 13 June 2020. Retrieved 29 July 2020.
  15. ^ Harris, Simon (29 July 2020). "Couple lose battle to save their dream home from HS2 bulldozers". ITV News. Retrieved 30 July 2020.
  16. ^ "Rise in injunctions against HS2 protesters". The Guardian. 13 June 2020. Retrieved 30 July 2020.
  17. ^ Horgan, Rob (27 April 2021). "How HS2 plans to reuse chalk slurry from Chilterns tunnel to 'rewild' the Colne Valley". newcivilengineer.com.
  18. ^ "Work begins to form HS2's Colne Valley Viaduct foundations". Global Railway Review. Retrieved 18 March 2021.
  19. ^ "First pier cast for Colne Valley viaduct [– with video]". www.theconstructionindex.co.uk. Retrieved 20 December 2021.
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