Peter Kenyon, TunnelTalk
- A study commissioned by HS2 is recommending an additional 9km of 8.7m diameter twin-running TBM-bored tunnel be added to the Phase 1 alignment between London and Birmingham.
- The revised alignment, which will run on to the existing Ruislip tunnel to create a single 14km-long tunnel, is almost certain to be implemented by the UK Department of Transport. The new recommendation follows an engineering study that was commissioned to investigate objections spearheaded by the local council in the London Borough of Ealing.
- The alignment change results in an almost continuous 22km-long tunnel under north and northwest London. Starting from just west of the terminus at the new Euston Station the amended alignment runs 8km through to the Old Oak Common station box and then, continuing eastwards, for a further 14km to the Ickenham Portal at West Ruislip.
New tunnel runs from Old Oak Common Station box, eastwards...
...where it joins existing 5km tunnel, removing the need for tunnel portals at Northolt and North Acton
- The decision cuts out the 9km-long overground part of the route between Old Oak Common Station and Northolt. Objectors led by the local council in Ealing pointed out that the existing plan would have required replacement or demolition of 20 bridges and a complete redesign of the busy Hanger Lane traffic intersection, one of the main choking points for commuter traffic from the west into central London.
- HS2 spokesman Adam Joyce told TunnelTalk: "We are recommending to the Department of Transport the addition of 9km of TBM-bored tunnel to create a 14km-long single continuous tunnel between Old Oak Common and West Ruislip. Our recommendation will now be subject to a new consultation period, but we expect the latest proposal will be acceptable because the consensus of local opinion is likely to be strongly in favour of the change." He added: "A more precise study of the cost of relocating and replacing bridges and utilities along the surface route revealed that they were similar to simply allowing the TBMs to continue from west of Old Oak Common Station through to Northolt and on to the planned portal at West Ruislip." According to the study the tunnel option will take 15 months less to construct, and will require an additional three vertical shafts though this will be compensated for by there now being no need for a tunnel portal at Northolt.
Complex Hanger Lane traffic gyratory system
- The recommendation announced today (23 April 2013) follows the addition last year of a further 5km of twin running tunnel alignment under the neighbouring London Borough of Ruislip, and the linking of two separate tunnels of 1.25km and 9.5km in rural Buckinghamshire to create a continuous 13.5km-long tunnel. Since the UK Government launched its consultation process for High Speed Rail 2 in 2010, an additional 16.5km of twin-running TBM bored tunnel and a further 8km of so-called 'green' cut-and-cover tunnels have been added.
- Initial scope for approximately 20km of TBM bored twin-running tunnels in four separate sections along the 224km route between London and Birmingham is now increased to 37km, plus an additional 8km of 'green' tunnels for a total underground alignment of 46.2km, or nearly 20%. Phase 2, between Birmingham and Manchester and Birmingham and Leeds, calls for a further 20.77km of TBM-bored twin running tunnels plus 1,560m of cut-and-cover tunnel.
- The HS2 spokesman said the decision to extend tunnelling as far west as Ickenham did not affect possible future plans for a high speed rail spur to Heathrow Airport, details of which have been delayed until after the Davies Commission on future airport capacity reports back to Parliament in Summer 2015. This additional planned route is expected to include a large element of tunnelling.
- Joyce said: "There will be an interchange at Old Oak Common for onward (non-high speed service) access to Heathrow. Any future (high speed) spur would start on a surface section from Ickenham out of London."
|Table 1. Underground alignments proposed for HS2 London-Birmingham|
|Location||Distance from Euston Station||Tunnel Length||Tunnel type|
|Euston Station - Old Oak Common Station box||500m - 8,500m||8,000m||TBM|
|Old Oak Common Station box||8,500m - 9,500m||1,000m||Station box|
|Portal west of Old Oak Common Station box - Ickenham Portal (West Ruislip)**||9,500m - 23,500m||14,000m||TBM|
|Chalfont St Peter - Little Missenden*||31,500m - 45,000m||13,500m||TBM|
|South Heath||46,500m - 47,600m||1,100m||Green|
|Wendover||53,500m - 54,600m||1,300m||Green|
|Turweston||95,000m - 95,100m||100m||Green|
|Greatworth||102,000m - 104,100m||2,100m||Green tunnel|
|Chipping Warden||110,000m - 112,500m||2,500m||Green|
|Ulton Woods||127,000m - 127,400m||400m||Green|
|Ulton Woods||127,400m - 128,900m||1,500m||TBM|
|Burton Green||146,000m - 146,520m||520m||Green|
* 2,400m tunnel section added January 2012
** 5,000m section (Northolt-Ickenham added January 2012), 9,000m section
(Old Oak Common Station box-Northolt added April 2013)
UK High Speed 2 needs 56km of twin tunnels - TunnelTalk, January 2013
Extra tunnels seal UK high speed rail approval - TunnelTalk, January 2012
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