Off the tourist track: Crossness Pumping Station

Sunday, August 14, 2016

Really this post should be in its own category called “Way way way off the tourist track” because even for an enthusiastic and experienced London tourist, this one was a push.  This is not just because it is bloody miles from anywhere.  I took me  fully four hours to get there and back, including 45 minutes on a bus each way, trundling through some of southeast London’s least picturesque industrial estates.  No, it’s not just the location that’s challenging.  The subject matter is also a bit of a stretch.  There’s no getting around it - a sewage pumping station is always going to be a tough sell to your average tourist.  However, if you’re going to spend the better part of a humid Sunday navigating your way to any sewage pumping station, surely Crossness must be at the top of the list of options.  (Also, I think by this point it’s fair to say I am by no means an average tourist.)

To fully appreciate the wonder and glory of Crossness Pumping Station we need a bit of historical background.  This time, back to the summer of 1858.  (Though Astute Go Stay Work Play readers will recall I’ve actually touched on this topic before.)  By this time waste management in London had progressed beyond the open sewers of the medieval era, with more than a hundred covered brick sewers having been built.  A few of these simply covered over some of London’s now-buried rivers like the Fleet and the Tyburn and these, along with a host of entirely manmade tunnels, emptied raw sewage directly into the Thames.  This system worked, more or less, until the population of London tripled from one to three million and until the flush toilet arrived on the scene, the combination of which resulted in a vastly increased amount of water and effluent being discharged into the Thames.  Naturally, this lent the river quite a pungent aroma which, combined with the unusually hot weather and low river levels during July and August of 1858 resulted in what is known as “The Great Stink”.  During a debate in Parliament (the buildings of which eventually had to be abandoned due to the stench) Disraeli called the Thames "a Stygian pool, reeking with ineffable and intolerable horrors”.  This, coupled with the increasing threat from cholera, meant something really needed to be done.

Luckily, British engineering came to the rescue.  You all know I’m a big fan of Isambard Kingdom Brunel, but this time we must tip our hats to another titan of the age: Sir Joseph Bazalgette (pronounced BAZ-el-jet).  A few years earlier, Bazalgette had proposed a system of giant gravity-fed tunnels running parallel with the banks of the Thames to intercept the existing sewer outfall and carry it downstream outside the greater metropolitan area.  With 82 km of large diameters tunnels and a network of 1,300 km of smaller sewers feeding them, under Bazalgette’s plan London’s sewage would be carried, stinklessly (yes, that it a word) downstream where it could be discharged into the river as the tide was flowing out to sea.  It was a monumental undertaking but just the kind of thing the Victorians liked to get stuck into, which they did.  Remarkably, those same tunnels are still in use today.

NPG x646; Sir Joseph William Bazalgette
Bazalgette.  What excellent facial hair.  You can practically taste those muttonchops!

I’m just going to say that again because I think it’s bloody amazing: London’s sewage is still efficiently and effectively carried in brick tunnels built by hand about a hundred and fifty years ago.  Apparently when calculating the diameter needed for the various sewer pipes, Bazalgette "took the densest population, gave every person the most generous allowance of sewage production and came up with a diameter of pipe needed. He then said 'Well, we're only going to do this once and there's always the unforeseen' and doubled the diameter to be used.” Joseph Bazalgette, you rock.

So what happened when all that waste made it out of London?  In order to be able to discharge it at the right time - when the tide would carry it out to sea - the waste needed to be pumped up out of the gravity fed tunnels that, by the time they reached their end point, were thirty to forty feet below sea level.  This required huge pumping capacity and therefore huge pumps.  Luckily, the Victorians were absolute demons at big steam-powered machines and Bazalgette’s designs for the system included not just the tunnels, but also the pumping stations to raise the effluent up into reservoirs ready for discharge.  The station on the north bank of the Thames is located at Abbey Mills and the one the south is at Crossness.  Also luckily, those Victorians did nothing by halves, and created not just highly functional but also truly beautiful machines.

The facade of the public entrance.  This building used to house the boilers.

Thus our historical background concludes and we can rejoin our weary blogger at the gates of Crossness Pumping Station on one of the very rare Open Days when they actually run - with steam - one of the giant old pumps that they’ve painstakingly restored, and let people wander around watching it all happen (which happens a mere six times this year).

I started out in a relatively new exhibition that told the story of London’s sewage - uplifting subject matter for a Sunday afternoon to be sure.  There were a lot of carefully researched information boards telling, in much greater detail than I’ve done here - the problem of sewage disposal, the risks from cholera, the history of the engineers involved, the impact of the system on the river, blah blah blah.  In truth, it was all pretty interesting stuff, but by far the most fun was the large display of historic toilets.

They also had a very informative display on toilet paper alternative used throughout history and in different cultures. (Including, if I recall correctly, corncobs and seashells.)

I absorbed as much information as I could, but in truth I really just wanted to go look at the giant machine.  The beauty of these Victorian engines is not just in the effectiveness and cleverness of the machine itself, but in the fact that the Victorians were particularly good at making machines not just functional but gorgeous.  Crossness Pumping Station is sometimes called “The Cathedral on the Marsh” because of its spectacular and brightly painted ornamental ironwork.

The main beam

Gratuitous but excellent Victorian frippery

And now settle down for a quick primer on beam engines, the particular bit of machinery on display at Crossness.  A beam engine is perhaps best described as a powered see-saw.  Steam power drives a big piston that pushes on one end of a giant beam (the tippy bit of the seesaw).  The other end of the beam is attached to a huge flywheel.  And in between, closer to the pivot point, are two shafts that lift plungers which actually pump the sewage, operating in opposition to one another and driven by the motion of the beam.  And when I say giant, I do mean that.  The main beam of a Crossness engine is 42’ long and the flywheel is 27’ in diameter and weighs 52 tons.  When in operation, each pump could lift 6 tons of sewage at a stroke, so one revolution of the flywheel would move 12 tons.  And considering that Crossness was equipped with four such engines, each running at about 10 RPM, that allows almost 5,000 tons of sewage to be moved every minute.  The Crossness Engine is thought to be the largest rotative beam engine still in operation in the world.  (The "rotative" part is the flywheel, which converts the uppy-downy motion of the beam to turny-roundy motion.  Sometimes beam engines are just uppy-downy.)

For steam-fans, the engine is a triple expansion, as is clearly obvious from the diagram.  Duh.

Bazalgette’s sewage system proved to be transformative for London.  The stink disappeared, along with the cholera that was thought, at the time, to be carried along with this “bad air”. Luckily, in wrong-headedly solving the problem of the smell, the Victorians also unintentionally eliminated cholera in the water supply, and outbreaks of typhus and tyhoid also decreased considerably.  However, let’s not forget that raw sewage was still being discharged into the Thames estuary, just not in London’s front garden.  (Unsurprisingly, the effect on downstream communities was not good.)  Now, of course, the sewage is treated properly, but London’s system still combines sewage and rainwater into the same sewers (unlike, for instance, Paris, where the two are separate).  And because the systems in London are combined, when there’s a large amount of rainfall in a short amount of time the system gets overwhelmed and they have to dump out into the Thames.  Yes, you read that right.  Even now, in 2016, London regularly dumps raw sewage into the river.  And not just a couple times a year.  Apparently this happens about once a week.  Seriously people?

Anyway, as I said, the station was equipped with four identical beam engines, loyally named “Victoria”, “Prince Consort”, “Albert  Edward” and “Alexandra”, located at the four corners of the Beam Engine House.  “Prince Consort” is the one that’s been restored, along with that corner of the room, while the rest of the space is decidedly unloved, which makes for an oddly divided space.  Most of the room has the sad but intriguing feeling of an abandoned warehouse or factory - dusty and rusted and full of seized up bits of machinery whose purpose one can only speculate about.

See what I mean?

And could you possibly devise a better setting for the final chase scene in a Sherlock Holmes adaptation that this?  It’s got “Hidden Supervillain Lair” written all over it.

Spin around though, and you’re presented with an improbable festival of colour.  It’s not just the engine itself that’s made of cast iron, the columns and floors and archways in the room are all made of the same material.  And all of it is decorated with scrolls and vines and lettering and embellishments of all sorts, and painted in an unexpectedly brash combination of colours.

This is part of the octagonal centre of the room, taken from the upper floor.

And here you can see where the restoration starts and stops.

It must have been a monumental amount of work to bring an engine back to life.  They were last run in the 1950s and at the time it was deemed uneconomic to dismantle them for scrap, which I guess is lucky.  Instead, as the Crossness website says, “...the pumps and culverts below the Beam Engine House were filled with a weak sand and cement mix to reduce the risks from methane. This has meant that some 100 tons of this sand had to be excavated from around and beneath the pumps before there was any hope of moving the beam and flywheel.”  That excavation had to be done before they could even start to get the machine working. (Not so lucky...)   The restoration of the overall site was started in about 1988 and is still ongoing, though the engine “Prince Consort” was working by 2003.  And it is magnificent.

Seeing something so large moving so gracefully and quietly is amazing.  I took a video but still have no luck in managing to get videos uploaded properly, so you’ll have to look at this much much much better one I found on Youtube.

It is running on steam, though the old enormous boilers are long gone.  Steam is now provided by a boringly tiny modern boiler from an industrial laundrette.

One of the reasons I like this video is that it shows the use of the barring engine.  I didn’t know what this bit of machinery was for, but the volunteers at Crossness are absolutely top notch and answered all my questions.  So - lucky you - you get to hear about barring engines! Because the beams are so massive the engines need a bit of help in getting started.  It was explained to me like this:  think about your bicycle pedals.  When you’re waiting to push off you instinctively position the pedals so that the pedal under the foot you’ll use to push off is at an advantageous angle.  If, for instance, it was sticking straight up or straight down you’d put your weight down on the pedal and it wouldn’t move.  It’s the same with a beam engine.  The beam needs to be at the most advantageous angle (just a bit above horizontal) in order to get going.  The barring engine drives a small gear (yay gears!) that can be meshed to teeth on the flywheel and used to position the wheel (and therefore the beam it’s attached to) in the correct place.  Normally this is done with steam power, but there’s also a backup manual version.

The backup manual barring engine

It was finding out about things like barring engines that made this such a great visit.  And really, the volunteers were lovely.  The ones who tend the engine wear sort of period clothing, and are clearly having a ball, even the guy who was using sort of a mini-mop to slop grease onto one of the moving pistons. (From the diagram, I'm guessing that's the low pressure cylinder.)

Surely for absolute historical accuracy this should have been done by a barefoot orphan dressed in rags, but I guess we can forgive that anachronism.

Even the people who ran the little café were dressed up, and served me a nice little pork pie and salad for a very reasonable sum, fortifying me for the long journey home.  And it was long.  By the time I got back to the boat, despite the fact that mostly all I’d done was sit on a long succession of buses and tube trains, I was utterly knackered.  So I had a nap and contemplated refitting the Lucky Nickel's smelly, noisy and intermittently non-functional diesel engine with a nice quiet steam driven engine painted bright red.

P.S.  Just to reassure you all - the fabulous patching system outlined in my last post is still holding strong.  In fact, I've decided that inch-thick layer of submarine grade epoxy is probably now the strongest part of the boat's hull.  And Jackie loved the flowers.  


Post a Comment