Crossrail starts restoration of Kingsway Subway

A disused tram tunnel under Holborn is set to be restored by Crossrail after it served an innovative purpose during the tunneling work in the area.

The long disused tunnel once carried trams under Kingway from Embankment to Holborn. The tunnel was closed in 1952 and the southern end was adapted as a traffic underpass in 1964.

Untouched save for the occasional use in films and art installations, the northern end was recently taken over by Crossrail, as it offered a very convenient location for some of their works.

During the construction of the large Crossrail crossover tunnel under Holborn, there was a slight risk of some subsidence affecting buildings on the surface, and one way to avoid that is to pump grout into the soil above the tunnels to compensate for the missing soil down at the tunnel.

This compensation grouting needs a shaft to be dug down in to the ground, and the Kingsway Subway happened came into service to provide a building site that had the advantage of not affecting road traffic above ground.

As the subway tunnel is Grade II listed, one of the conditions of allowing Crossrail to dig their tunnel was that they should restore the tunnel afterwards, and a planning application filed last week has confirmed that they are now at that stage.

Now that the compensation grouting shaft has gone out of use the majority of the rings below ground are to be left in place, and the shaft will be backfilled, most likely with lean mix concrete / PFA up to the level of the uppermost level of rings.

These upper rings will be removed along and the whole area backfilled with compacted crushed limestone and sand blinding to match the existing levels. The concrete floor of the tunnel will be reinstated with new concrete cast in-situ to replicate the appearance of the existing. Where setts and/or inspection covers have been removed beneath the concrete these will be reinstated as found.

Where granite cobbles ( setts) have been removed, concrete will be laid over them once they are reinstated, in order to reinstate the floor of the tunnel as found.

The iron tram rails will then be reinstated to their original locations.

And the tunnel will go back to sleep once more.

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12 comments on “Crossrail starts restoration of Kingsway Subway
  1. Melvyn says:

    Just as work for Crossrail finishes work to upgrade Holborn Station approaches so maybe Tram Subway May be used again as part of that project !

  2. GT says:

    Steel Rails, actually

  3. Tony Woolf says:

    Is it a bit silly to lay cobbles only to cover them with concrete? Cobbles are just cobbles, and any information about exactly how they were laid has already been lost. If the concrete is ever removed in the future, what people will see is a 2017 rebuild. It’s not like archaeological sites that are re-buried, those haven’t been destroyed and re-built.

  4. Ronald Wallman says:

    As far as I can remember having ridden on trams through this subway the exit ramp in Southampton road is cobbled but the subway itself is concrete floor with steel rails embedded in it including crossovers all using conduit current collection. There are all sorts of problems involved in running trams here again not least of which very few remaining trams have conduit gear and the ramp is one of the steepest tramways even on a global scale only allowing one car on it at a time and hazardous to use today.

    • scott mcintosh says:

      Having been in the tramway industry for 30+ years, including being Leader of the Tramlink Proect Team, Project Director for the Cross River Tram and TfL’s only Principal Officer, Trams and Trolleybuses I can confirm Ronald’s points about the Kingsway Subway.

    • Alan says:

      Why only one car at a time on the access ramp section of the tramway?

  5. Ronald Wallman says:

    Tram rails in London are based on BS2 (British Standard 2) and are rolled from steel as can be seen and ridden on at venues such as Crich and The East Anglia Transport museum that currently has tram 1858 that has conduit gear and a plough that if it is in working order and the conduit in working condition and energised could be used through the subway. Had the rails been iron especially wrought iron like the Eiffel Tower and SS Great Britain they would wear away in no time but be amazing resistant to rust and concrete will preserve steel but not the exposed surfaces. Please note it was always called a subway and that the south end has two unused exits one under Waterloo bridge and the other immediately to the west that is sealed up there but for one very low doorway in what is now the Strand underpass. This hidden cavity still has tram rails and the floor is hollow and underneath is the original Thames river bed.

  6. Isabel White says:

    Can we access the sealed sections for open house too?

  7. Julius Stafford-Baker says:

    The Northern End, not just films and art installations, but
    at one-time slightly secret Government offices, possibly Observer Corps type of thing, later floods control for the GLC

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