HS2 London

Colne Valley Viaduct: 1 Year In

It’s just over one year since I last had a detailed look at the worksite for the forthcoming Colne Valley Viaduct, and I was back last week to see what’s changed.

Launch Girder

The viaduct is being built north to south, and this striking red structure, the launch girder, has just been assembled on the earthworks leading to the northern end. It will soon take a slow journey, sliding the couple of miles across the viaduct, atop the newly created piers, building the main bridge deck from the precast sections being created at an onsite factory.

The launch girder sitting on the northern viaduct embankment.
Unusual site speed restriction sign.


These are now appearing regularly, in various stages of completeness stretching along the first part of the viaduct. The plan I believe is to create one a week.

The second pier.
The sixth pier, with concrete surface texture detail visible.
The seventh pier, being shuttered while the concrete sets from being poured. The ex-Denham Water-ski Club hut is behind.
Rebar for the eighth pier in place, nearly ready to be shuttered.

The pair either side of the A412 (Nos. 3 and 4) have a different design, as they are angled, to support the viaduct which will cross the road here at a severe skew angle.

Grand Union Canal

The Grand Union Canal is one crossing that needs to stay open as much as possible – so the haul road will not cross it. Instead, two haul roads will meet either side of it. Here, the photo shows the southern limit of the northern haul road pontoon on Savay Lake, with the forthcoming piers of the viaduct due to appear on the left.

Southern end of the northern haul road, by the Grand Union Canal towpath.

Reflectors for a survey robot have been embedded beside the canal here on its towpath here, at the point that viaduct will cross, to check there’s no movement or subsidence of the canal or towpath here when the piers or viaduct deck go on – particularly important as the land and lake to the west of the towpath is slightly below the canal level.

Survey reflector on the towpath.

Haul Road Pontoon

On the other side of the canal, another haul road pontoon, coming across Broadwater Lake from the south and London. It may advance a little bit more, across the track and cycle route here, and up to the other side of the Grand Union Canal. The viaduct piers will be on the right. It will likely be over a year before these ones get constructed, as this is the southern end of the viaduct. The closed, but not yet relocated, Hillingdon Outdoor Activity Centre, is just to the right of the far end of the pontoon here – spared a direct hit by a late design change in the HS2 route, but still likely to move to be on a different lake.

The haul road crossing Broadwater Lake.
Southern haul road pontoon – current end.


Construction Open Doors

Construction Open Doors 2017 is almost here – various building sites and other construction projects are opening up to the public next week. Many sites are still bookable.

I’ve booked five sites to look around next week – King’s Cross Central, Waterloo International, Alexandra Palace, Battersea Power Station and Crossrail Whitechapel. I’ve visited two of these sites before so it will be interesting to see what’s changed.

Look out for a writeup of each of the above in the next few weeks.