A small octagonal brick building in docklands conceals a marvellous secret – an 18 metre deep Victorian shaft that is used to pump out water that leaks into the Connaught railway tunnel that runs under the docks.

Head House Shaft surface building

If you are digging a tunnel through wet soil, it may surprise you to learn that they are never built to be fully watertight, but to leak, a little bit.

It is not impossible to make a watertight tunnel, but frankly, not worth the extra cost and difficulty involved. Also, if it is a railway tunnel, then the structure shifts in the soil and is shaken by the trains, so any waterproof membrane will break fairly swiftly.

So, built a decently waterproof tunnel, but also put in facilities to pump out the water that is designed to leak into it.

One such tunnel is the Connaught Tunnel in docklands, which was built not so much in wet soil than in soaking wet marshland, which is even worse. As such a pumping station was added to drain the water out and has been running ever since the tunnel was built around 130 years ago.

As long-term readers may recall, this will eventually be converted to be part of the Crossrail network, and those works will lower the base of the tunnel by about a metre.

As such, the pumping facilities need to be upgraded.

Sadly, the bit you can see above ground has to go as it no longer meets modern standards for a building housing industrial services. Fortunately although the building has to go, it is to be taken down rather carefully, and the current expectation is that it is being given to the SS Robin, a steam ship and will be probably rebuilt next to the ship as its ticket-shop.

Both are of a comparable age, so there is historic synchronicity.

Although I have known about the little brick building for ages, and more recently found out its function, I had presumed the building concealed the pumps and there were just narrow pipes drilled down to the tunnel below. You can imagine my loud squeak when shown the following image at a previous Crossrail site visit!

Image Copyright: Crossrail

Not a small building sitting on top of a pipe, but an entire shaft dug down with stairs and landings and all sorts of exciting things.

Fortunately, the people at Crossrail decided to let a group of us back into the Connaught Tunnel for a look earlier this week (more about that in a day or two), and oh, as you are here, lets take a look inside the brick building.

Inside the surface building

We were only allowed to look down from the ground level, as to go down requires a special confined spaces permit which is particularly important here as the bottom of the shaft is flooded.

That flooding is deliberate, as the water is drained out of the railway tunnel into the shaft, then pumped away. That way the shaft itself acts as a storage tank should there be unusually high amounts of water leaking into the tunnel at any time.

We could see, and hear the water gushing away at the bottom of the shaft, although the photos didn’t quite capture that.

Looking down

As mentioned, and visible in the slide above, the shaft will be cleared out and then deepened. To allow that to happen, the engineers are just now starting to install wells of their own around the site which will “dewater” the area – aka, dry it out, so that the shaft can be underpinned with the new deeper structure.

The works to deepen the shaft will be undertaken using heavy equipment that will be lowered down through the existing shaft to the sump beneath. The complete removal of the existing headhouse building is required to enable these works.

There are currently three pumps located at the base of the pump shaft. These will be replaced by four larger pumps. The existing headhouse provides very limited space around the pump shaft. The replacement building will provide additional space to enable access and maintainability of the new, larger pumps. The installation of the four pumps, rather than the existing three, requires the provision of a swing jib to enable placement of the pumps in the required location within the sump. An enlarged headhouse is required to accommodate this equipment.

There will in fact be two buildings, as more equipment will be in a concealed building away from the shaft. That helps to keep the replacement shaft head building to something closer in size to the original.

Although there is understandably a lot of public focus on the tunnels and stations, it is often these smaller enabling works that are more interesting as they show an aspect of the project that is sometimes overlooked and remind us that a tunnel is rarely just a tunnel alone.

Looking down

Thanks to the team at Crossrail for the site visit.

Roof view

The old support arm for lifting work

Three pumps working as we were on site.

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12 Comments

  1. mary

    I follow your tweets but I know you don’t know me and you never react to tweeted replies. So many of these sites are ones many of us visited years ago – do you research some of these past., often very detailed, reports.
    This is not really supposed to be a public comment so please delete it. I just sometimes feel that you are following me around 15 years later.

    • IanVisits

      The entirety of the content in this particular blog post is based on information gleaned from talking to Crossrail/Vinci staff and the planning applications submitted to Newham Council.

      If I have found information on a website showing a previous visit, then I usually remember to link to the source.

      Curious to know how you got inside the buildings and tunnels I visited in the area, as they have always been off-limits to the general public.

  2. RobH

    Another side to Crossrail construction rarely considered. Good post as usual Ian, it’s not just tunnels and stations!

  3. mary

    I guess a lot of stuff never got on the web – too long ago. I’ll find out how from others.
    Please delete these comments of mine though.

    - but nice to hear about Kew Bridge. They deserve it

  4. That pump control panel doesn’t look 130 years old. How long ago were the present pumps installed?

    • IanVisits

      That I couldn’t find out – but I would guess things like that have to be replaced every few decades as they wear out.

  5. Alan Burkitt-Gray

    Pity Crossrail doesn’t know the difference between “uncharted” and “unchartered”. Why should soil have a charter?

    • IanVisits

      I think you’ll find they do know the difference, and the issue you cite is quite obviously just a typo.

  6. Ana

    Very very interesting! I would love to visit it!

  7. Chris M

    Are there plans online anywhere that show what the replacement building will look like?

    • IanVisits

      Not that I was able to find as I was looking for them myself. There are some line drawings in the planning application but no “artists renders” of the finished building.

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