{{Short description|HS2 Railway Bridge in Harefield}} {{Distinguish|Colne Viaduct|text=the [[Colne Viaduct]]}} {{Use dmy dates|date=August 2025}} {{Use British English|date=August 2025}} {{Infobox bridge | name = Colne Valley Viaduct | image = Looking North Korda lake. used in Chiltern mag number 255 2025 Harefield.2.jpg | caption = Viaduct in January 2025 over [[Mid Colne Valley#Broadwater Lake|Korda Lake]] | coordinates = {{Coord|51.5859|-0.4900|display=inline,title|region:GB_type:landmark}} | os_grid_reference = | carries = [[High Speed 2]] | crosses = [[Colne Valley Regional Park]] | locale = {{ubl|[[Harefield]]|[[Denham, Buckinghamshire|Denham]]}} | official_name = | maint = | heritage = | operator = | traffic = High speed passenger trains | notrack = 2 | gauge = {{Track gauge|Standard gauge}} | electrification = {{25 kV 50 Hz AC}} | length = {{convert|3.38|km}} | width = {{convert|14.3|m}} | height = c.{{convert|10|m}}<ref name = "rail engineer"/> | mainspan = {{convert|80|m}} | number_spans = 57 | piers_in_water = 11 | open = | opening = | engineering = Rendel-Ingerop, [[Jacobs Solutions|Jacobs]] | builder = Align JV ([[Bouygues Travaux Publics]], [[Sir Robert McAlpine]] and [[VolkerFitzpatrick]]) | begin = March 2021 | complete = {{ubl|September 2024 (deck)|September 2025 (structure)}} | architect = {{ubl|[[Grimshaw Architects|Grimshaw]]|Knight Architects - concept|LDA Design - landscape}} | extra = }}
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 [[London Borough of Hillingdon|Hillingdon]], [[Greater London]] and [[Denham, Buckinghamshire|Denham]] in [[Buckinghamshire]]. At a length of {{convert|3.38|km|abbr=in}} and a weight of 116,000{{nbsp}}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 {{convert|320|km/h|mph|abbr=in}} 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 purchase|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.
==Design== 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.<ref name="rail engineer">{{cite web |date=7 June 2021 |title=Colne Valley Viaduct – HS2’s largest bridge |url=https://www.railengineer.co.uk/colne-valley-viaduct-hs2s-largest-bridge/ |publisher=railengineer.co.uk}}</ref><ref>{{Cite web |date=24 November 2023 |title=River Blythe Viaduct Design and Access Statement - Addendum |url=https://publicaccess.solihull.gov.uk/online-applications/applicationDetails.do?activeTab=summary&keyVal=S4W0FZOE01100 |website=solihull.gov.uk |publisher=HS2 Ltd |page=18}}</ref> Its basic configuration is a gently-curved structure along a horizontal radius of {{cvt|5280|m}}, supported by 57 spans, with 11 V-shaped piers in water, and weighing roughly 116,000{{nbsp}}tonnes in total.<ref>{{Cite web |last=Tonks |first=Simon |date=1 June 2023 |title=Colne Valley viaduct piers start to take shape {{!}} ST Selection |url=https://st-selection.co.uk/colne-valley-viaduct-piers-start-to-take-shape/ |access-date=2 June 2025 |language=en-GB}}</ref> The viaduct crosses over both the [[River Colne, Hertfordshire|River Colne]] and the [[Grand Union Canal]], at which points its spans are spaced at intervals of {{cvt|80|m}}; the majority of over-land spans cover shorter lengths of either {{cvt|45|or|60|m}}.<ref name="grimshaw 2020">{{Cite web |title=HS2 Colne Valley Viaduct |url=https://grimshaw.global/projects/colne-valley-viaduct/ |access-date=28 July 2020 |website=Grimshaw}}</ref><ref name="rail engineer" /> Trains will travel at about {{convert|320|km/h|mph|abbr=in}} on the bridge.<ref name=":0">{{Cite web |date=2025-09-10 |title=HS2 finishes Colne Valley Viaduct, 'UK's longest railway bridge' |url=https://www.bbc.com/news/articles/cvg9pl1rg72o |access-date=2025-09-15 |website=BBC News |language=en-GB}}</ref>
Considerable attention has been directed to the viaduct's aesthetic design and to avoid unnecessarily impacting the surrounding landscape and local community.<ref name="rail engineer" /> To reduce its impact upon wildlife and the general public alike, {{convert|4|m|adj=on|spell=in}} 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.<ref name="grimshaw 2020" /> The design of the [[Overhead line|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.<ref name="rail engineer" /> However, the viaduct has been subject to criticism from [[Stop HS2]] for allegedly ignoring the needs of local residents.<ref name="BFP">{{cite news |last1=Wareham |first1=Stephanie |date=24 January 2018 |title=Campaigners criticise HS2 plans for 'one of the longest viaducts in UK' |url=https://www.bucksfreepress.co.uk/news/15893530.campaigners-criticise-hs2-plans-for-one-of-the-longest-viaducts-in-uk-in-the-colne-valley-regional-park/ |accessdate=29 July 2020 |work=Bucks Free Press |language=en}}</ref> 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.<ref name="rail engineer" />
The main deck of the viaduct was manufactured at a nearby temporary factory, the assembly of which was commenced from the northern end.<ref name="rail engineer" /><ref>{{cite web |last=Horgan |first=Rob |date=14 June 2021 |title=The reality of working on HS2’s biggest construction site |url=https://www.newcivilengineer.com/latest/the-reality-of-working-on-hs2s-biggest-construction-site-14-06-2021/ |publisher=newcivilengineer.com}}</ref> In total, 908 deck units and 92 pier head units were produced; weighing between 60 and 140{{nbsp}}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.<ref name="rail engineer" /> 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{{nbsp}}tonnes, a total of four [[shock absorber]] units were integrated into the deck structure of the viaduct.<ref name="rail engineer" /> The structure also features four [[Expansion joint|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.<ref name="rail engineer" />
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 “''[[Glossary of French words and expressions in English#tour de force|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.<ref>{{Cite web |title=Winners 2024 |url=https://buildingbeautyawards.com/winners-2024/ |access-date=2025-08-20 |website=Building Beauty Awards |language=en-US}}</ref><ref>{{Cite web |date=2024-11-22 |title=HS2 Colne Valley viaduct scoops prestigious design award |url=https://mediacentre.hs2.org.uk/news/hs2-colne-valley-viaduct-scoops-prestigious-design-award |access-date=2025-08-20 |website=HS2 News and Information |language=english}}</ref> ''[[The Times]]'' called the bridge "a two-mile-long masterpiece".<ref>{{Cite web |last=Bleach |first=Stephen |date=14 August 2025 |title=Britain’s longest rail bridge: how we built HS2’s Colne Valley Viaduct |url=https://www.thetimes.com/uk/transport/article/britains-longest-rail-bridge-how-we-built-hs2s-colne-valley-viaduct-nr9mwzlxr |access-date=2025-09-15 |website=The Times |language=en}}</ref>
==History==
=== Planning === Various means for [[High Speed 2]] to traverse the valley of the [[River Colne, Hertfordshire|River Colne]] 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.<ref>{{Cite web |date=27 February 2015 |title=Proposal for Northern Extension of Northolt Tunnel SIFT Report |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/410306/C222-ATK-DS-REP-020-000034_P06_with_drawings.pdf |url-status=live |access-date=3 July 2020 |website=High Speed 2|archive-url=https://web.archive.org/web/20190726141637/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/410306/C222-ATK-DS-REP-020-000034_P06_with_drawings.pdf |archive-date=26 July 2019 }}</ref> During 2017, Contract C1 (Central 1), which covers the 21.6 km 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]].<ref name="rail engineer" /> RC Works were carried out by Kilnbridge Construction Services.
On 19 January 2018, the design concept for the Colne Valley Viaduct, which was created by Knight Architects and [[Atkins (company)|Atkins]], was unveiled by the British Government.<ref>{{Cite web |title=HS2 reveals Colne Valley viaduct concepts |url=https://www.gov.uk/government/news/hs2-reveals-colne-valley-viaduct-concepts |access-date=28 July 2020 |website=GOV.UK |language=en}}</ref><ref>{{cite web |url = https://www.newcivilengineer.com/archive/hs2-reveals-controversial-colne-valley-viaduct-19-01-2018/ |title = HS2 reveals controversial Colne Valley viaduct |publisher = newcivilengineer.com |date = 19 January 2018 |first = Katherine |last = Smale}}</ref> This concept was produced in consultation with the Colne Valley Regional Park Panel.<ref name = "rail engineer"/> Additional work on the viaduct's design has also been undertaken by [[Grimshaw Architects]].<ref>{{Cite web |last=Hopkirk |first=Elizabeth |last2=Rogers |date = 15 April 2020 |first2=Dave |title=Huge boost as government tells HS2 to start work |url=https://www.bdonline.co.uk/news/huge-boost-as-government-tells-hs2-to-start-work/5105539.article |access-date = 28 July 2020 |website=Building Design |language=en}}</ref>
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.<ref name="NCE">{{cite news |last1=Smale |first1=Katherine |title=HS2 and council clash over Colne Valley viaduct 'uncertainty' |url=https://www.newcivilengineer.com/latest/hs2-council-clash-colne-valley-viaduct-uncertainty-06-08-2019/ |accessdate=29 July 2020 |work=New Civil Engineer |date=6 August 2019 |language=en}}</ref> 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.<ref>{{cite web |url = https://www.hillingdontimes.co.uk/news/19174264.hillingdon-hs2-declare-peace-plans-colne-valley-viaduct/ |title = Hillingdon and HS2 declare peace over plans for Colne Valley Viaduct |publisher = hillingdontimes.co.uk |date = 19 March 2021}}</ref> Shortly following this decision, full planning permission for the viaduct was secured.<ref name="plan approve">{{cite web |url = https://www.newcivilengineer.com/latest/hs2-secures-full-planning-consent-for-uks-longest-rail-bridge-after-council-drops-legal-challenge-01-04-2021/ |title = HS2 secures full planning consent for UK’s longest rail bridge after council drops legal challenge |publisher = newcivilengineer.com |date = 1 April 2021 |first = Rob |last = Horgan}}</ref>
=== Preparation works === As early as 2018, protestors had taken up positions in the Colne Valley to voice their objections to the project.<ref>{{cite web |url = https://www.theguardian.com/uk-news/2020/dec/08/veteran-activist-swampy-among-protesters-in-hs2-site-standoff-with-police |title = Veteran activist Swampy among protesters in HS2 site standoff with police |publisher = theguardian.com |first = Gwyn |last = Topham |date = 8 December 2020}}</ref> In April 2019, 12 [[Extinction Rebellion]] protesters began [[treesitting]] in order to prevent trees being chopping down as part of preparatory works at Harvil Road, near to the proposed site of the viaduct.<ref name="Independent-270419">{{cite news |last1=Snaith |first1=Emma |title=Extinction Rebellion activists camp out in trees to protest HS2 |url=https://www.independent.co.uk/news/uk/home-news/extinction-rebellion-hs2-trees-climb-colne-valley-hillingdon-a8889401.html |accessdate=29 July 2020 |work=The Independent |date=27 April 2019 |language=en}}</ref> There had been a protest camp next to the road since October 2017, which HS2 began evicting in January 2020.<ref name="Guardian070120">{{cite news |last1=Taylor |first1=Diane |title=HS2 begins evicting activists from protest site after two years |url=https://www.theguardian.com/uk-news/2020/jan/07/hs2-begins-evicting-activists-from-protest-site-after-two-years |accessdate=29 July 2020 |work=The Guardian |date=7 January 2020 |language=en |archive-url=https://web.archive.org/web/20200613074802/https://www.theguardian.com/uk-news/2020/jan/07/hs2-begins-evicting-activists-from-protest-site-after-two-years |archive-date=13 June 2020 |url-status=live }}</ref>
In order to clear the viaduct's intended path, a farmhouse was [[compulsorily purchase]]d while a [[watersports]] centre was required to relocate. Both properties were demolished.<ref>{{Cite web |last=Harris |first=Simon |date=29 July 2020 |title=Couple lose battle to save their dream home from HS2 bulldozers |url=https://www.itv.com/news/london/2020-07-28/harefield-couple-lose-seven-year-battle-to-save-their-dream-home-from-hs2-bulldozers |access-date=30 July 2020 |website=ITV News |language=en}}</ref><ref>{{cite news |date=13 June 2020 |title=Rise in injunctions against HS2 protesters |url=http://www.theguardian.com/uk-news/2020/jun/13/rise-in-injunctions-against-hs2-protesters |last1=Taylor |first1=Diane |last2=Barkham |first2=Patrick |access-date=29 December 2022 |publisher=The Guardian |language=en}}</ref> Various preparatory works were also undertaken during the 2010s, including the diversion of water mains, the realignment of a 275{{nbsp}}kV overhead power line, the reinforcement of a gas main, along with other measures.<ref name="rail engineer" /> Towards the northern end of the viaduct, a temporary construction compound was 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 {{convert|3000000|m3|abbr=off}} of chalk slurry was also been provisioned for the construction of the [[Chiltern tunnel]] to the north of the viaduct.<ref name="rail engineer" /><ref>{{cite web |url = https://www.newcivilengineer.com/latest/how-hs2-plans-to-reuse-chalk-slurry-from-chilterns-tunnel-to-rewild-the-colne-valley-27-04-2021/?tkn=1 |title = How HS2 plans to reuse chalk slurry from Chilterns tunnel to ‘rewild’ the Colne Valley |publisher = newcivilengineer.com |date = 27 April 2021 |first = Rob |last = Horgan}}</ref>
===Construction=== [[File:HS2 Colne Valley Viaduct Under Construction Jan 31 2023 Piers under construction.jpg|thumb|right|Colne Valley Viaduct bridge piers under construction in January 2023.]][[File:HS2 Colne Valley Viaduct Under Construction Jan 31 2023 showing workers and cross section.jpg|thumb|Construction in January 2023 showing the bridge deck cross section.]][[File:Colne Valley Viaduct construction across the Harefield 2 lake in April 2024.jpg|thumb|Construction gantry in April 2024]] [[File:Curve of the Colne Valley Viaduct.jpg|thumb|Viaduct under construction in June 2024]] During March 2021, construction of the viaduct's foundations commenced, although test piling had occurred before this.<ref>{{Cite web |title=Work begins to form HS2's Colne Valley Viaduct foundations |url=https://www.globalrailwayreview.com/news/119361/hs2-colne-valley-viaduct-foundations/ |access-date=18 March 2021 |website=Global Railway Review |language=en}}</ref> 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 May 2022, deck construction commenced from the northern embankment.<ref>{{cite news |url=https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-61642870 |title=HS2: Work begins on 'UK's longest railway bridge' in Buckinghamshire |publisher=BBC News |date=31 May 2022 |accessdate=29 December 2022}}</ref>
In December 2021, the first {{convert|6|m|ft|spell=in|adj=mid|-tall}} pier for the viaduct was cast.<ref>{{Cite web|title=First pier cast for Colne Valley viaduct [– with video]|url=https://www.theconstructionindex.co.uk/news/view/first-pier-cast-for-colne-valley-viaduct-with-video|access-date=20 December 2021|website=www.theconstructionindex.co.uk|language=en}}</ref><ref name = pbctoday1 >{{cite news | url = https://www.pbctoday.co.uk/news/planning-construction-news/hs2-colne-valley-viaduct-2/103067/ | title = HS2 creates the first of 56 giant piers for Colne Valley Viaduct | date = 20 December 2021 | newspaper = Planning, BIM & Construction Today | access-date = 4 February 2022}}</ref> Construction of four jetties across the lake was also completed to support work on the piers that will be built in the water.<ref name = pbctoday1 /> In June 2022, the launching girder named ''Dominique'' started construction.<ref>{{Cite web |title=HS2 celebrates start of construction on UK’s longest railway bridge |url=https://mediacentre.hs2.org.uk/news/hs2-celebrates-start-of-construction-on-uks-longest-railway-bridge |access-date=3 June 2022 |website=HS2 News and Information |language=english}}</ref> By December 2022, 125 of the 1,000 bridge segments had been placed in their final position.<ref>{{cite news |url=https://www.newcivilengineer.com/latest/hs2-construction-progresses-on-record-breaking-colne-valley-viaduct-15-12-2022/ |title=HS2 Construction progresses on record-breaking Colne Valley Viaduct |publisher=New Civil Engineer |date=15 December 2022 |last=Hakimian |first=Rob |accessdate=29 December 2022}}</ref>
Construction reached the half-way point (1.7 km) in November 2023.<ref>{{Cite web |last=Pearson |first=Gavin |date=9 November 2023 |title=HS2 {{!}} Construction of UK's longest rail bridge reaches halfway point |url=https://www.newcivilengineer.com/latest/hs2-construction-of-uks-longest-rail-bridge-reaches-halfway-point-09-11-2023/ |access-date=29 February 2024 |website=New Civil Engineer |language=en}}</ref> In February 2024, construction was halted for "urgent remedial works" in the week before the launching girder was due to begin crossing the [[Grand Union Canal]]. This involved repeating cable tensioning in the most recently completed span, which includes drilling out the concrete join.<ref>{{Cite web |last=Johnson |first=Thomas |date=20 February 2024 |title=HS2 {{!}} Colne Valley Viaduct construction halted for ‘urgent remedial works’ |url=https://www.newcivilengineer.com/latest/hs2-colne-valley-viaduct-construction-halted-for-urgent-remedial-works-20-02-2024/ |access-date=29 February 2024 |website=New Civil Engineer |language=en}}</ref> The final pre-cast deck segment, at [[Denham, Buckinghamshire|Denham]] in [[Buckinghamshire]],<ref>{{cite news | url = https://www.bbc.co.uk/news/articles/c8dpn9219nvo | work = BBC News | title = HS2 completes work on 'longest railway bridge'|first1 = Danny | last1 = Fullbrook |last2 = PA Media| date = 5 September 2024 | access-date = 30 June 2025}}</ref> was installed on 5 September 2024.<ref>{{Cite web |date=5 September 2024 |title=Britain gets its new longest rail bridge in major HS2 milestone |url=https://mediacentre.hs2.org.uk/news/britain-gets-its-new-longest-rail-bridge-in-major-hs2-milestone |access-date=5 September 2024 |website=HS2 |language=english}}</ref> The viaduct was structurally complete by August 2025, with the installation of "parapets, noise barriers, robust kerbs, waterproofing, internal drainage and structural health monitoring systems".<ref>{{Cite web |date=12 May 2025 |title=Colne Valley Viaduct |url=https://www.hs2.org.uk/building-hs2/viaducts-and-bridges/colne-valley-viaduct/ |access-date=30 June 2025 |website=[[HS2]] |language=en-GB}}</ref> By September 2025, Align JV announced that bridge was fully complete.<ref>{{Cite web |last=Johnson |first=Thomas |date=2025-09-10 |title=HS2: Align JV fully completes Colne Valley Viaduct, the UK's new longest railway bridge |url=https://www.newcivilengineer.com/latest/hs2-align-jv-fully-completes-colne-valley-viaduct-the-uks-new-longest-railway-bridge-10-09-2025/ |access-date=2025-09-15 |website=New Civil Engineer |language=en}}</ref><ref name=":0" /> Track, power, signalling and other systems will subsequently be installed by various contractors to allow trains to operate.<ref>{{Cite web |date=26 November 2024 |title=HS2 confirms rail systems contract winners |url=https://mediacentre.hs2.org.uk/news/hs2-confirms-rail-systems-contract-winners |access-date=2025-09-15 |website=HS2 |language=english}}</ref>
==References== {{reflist}}
==External links== *{{Commons category-inline}}
{{High Speed 2 articles}} {{Authority control}}
[[Category:Bridges under construction]] [[Category:Concrete bridges in England]] [[Category:High Speed 2]] [[Category:Railway viaducts in Buckinghamshire]] [[Category:Railway viaducts in London]]