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00:01Britain's history is recorded in its monuments.
00:05Even before the Normans came and built their castles across the country,
00:08successive generations have left their mark on the landscape,
00:12in the landmarks they've left behind.
00:15But now those landmarks are crumbling.
00:18There's a section there which is quite bad.
00:20Centuries of wear and tear have taken their toll on these precious buildings.
00:24More of the structural members were suffering from corrosion than we expected.
00:28There's moss growing inside, so then the water backs up, then falls internally.
00:33They need constant care and maintenance in all kinds of conditions.
00:39You can see dust coming up.
00:40A hundred years old dust.
00:42Revealing treasures that have been hidden for centuries.
00:45We're unearthing the original bridge.
00:47All over the country, teams of highly skilled people are dedicating their lives
00:52to keeping our heritage standing.
00:54We need to be aware that we are part of a cycle that's been going on for centuries.
00:59These are Britain's landmark fixers.
01:02And this is not just their story.
01:04They took me nearly 6,000 old to drill.
01:07How marvellous.
01:08But the story of the buildings they look after.
01:11London is home to some of the greatest engineering marvels of the 19th century.
01:32But the most impressive piece of Victorian engineering in the city is invisible.
01:40It lies beneath the streets.
01:44It's a 1,300 mile long sewer that saved the population of the capital from one of the greatest killers of the age.
01:53But today, it's struggling to cope.
02:05Sewage absolutely never stops.
02:0824 hours a day, this site is manned.
02:12Christmas Day, bank holidays, Sundays, there's always a team here.
02:16Because obviously, if anything major happened, people need to be here to sort it out very quickly.
02:25John Clifton looks after Mogden sewage treatment works on the western edge of the city.
02:31It was built at a time when Londoners had a lot less to flush away.
02:35We're going back a long, long time before sanitary towels, antiseptic whites, cotton buds were even invented.
02:43So obviously, the system is trying to catch up with modern day life.
02:46And it's just finding it very hard to keep up.
02:50We get the weirdest things that come through the sewers here at Mogden.
02:54Anything from half a dead dog to footballs to amount of rag that we have to kind of get out.
03:00We want to get it out before it ruins some pipes or some of the machinery.
03:05When London sewer workers talk about rag, they don't mean old bits of fabric.
03:11So I'm having a look at this screen here.
03:13Straight away, I can see a rag roll down the bottom.
03:16So we want to get that out now before it gets too big.
03:19Because otherwise, we'll need an overhead frame to get it out.
03:22I can probably manually do that.
03:23So basically, this is called a rag roll.
03:31This is combined sanitary towels, wet wipes, cotton buds.
03:36It churns together, gets tighter and tighter.
03:40We call it a rag roll because it looks like a carpet.
03:44OK, so this is what we just got out now.
03:47So as you can see, if you open it, it's all combined, it's congealed, it's stuck together.
03:55If we left that in there for longer, that rag will get bigger, bigger, bigger and bigger.
04:02And in the end, it will stop the screens from working.
04:05You get two or three of these screens going out.
04:07Now you're going to get flooding.
04:09Everything will start going wrong.
04:11Sooner or later, it's going to block something up.
04:12Floods in London are becoming more common as climate change brings harder rainfall
04:18and the concrete-covered metropolis stops water escaping.
04:22When London gets a deluge, sewage overflows into the River Thames.
04:27These sewers were built for a population of three million people.
04:31Now there are over eight million and they're struggling to cope.
04:36Humans and raw sewage don't mix.
04:38Londoners back in the 1850s had an average life expectancy of 40 years.
04:44London in the 1850s was a stinking cesspit.
04:48London was pockmarked by cesspits.
04:51They collected human excrement underneath the privies,
04:55but they leaked into the groundwater, contaminating it.
04:58And the problem is that all of the sewage, all of the industrial waste,
05:03was all being dumped in the Thames.
05:05The problem got worse as London's population grew.
05:09Almost a million perhaps in 1800 and two million by 1850.
05:15Many of them had flushing toilets which added to the amount of volume of sewage that was going into the river.
05:21Cartoons of the period show all kinds of horrible diseases emerging from the river.
05:26The biggest killers were typhoid and cholera.
05:31Between 1853 and 1854, more than 10,000 Londoners were killed by cholera.
05:38The most common theory was that disease was spread by miasma, which is the smell.
05:43They thought it was the actual smell that was spreading cholera.
05:48London was in crisis.
05:54Joseph Bazalgette was a visionary engineer.
05:58He was called in as the sewage problem got so bad the government of the nation was starting to falter.
06:04So Bazalgette believed if you could keep the smell from getting to people, then these airborne diseases would come to an end.
06:15Bazalgette had a radical and ingenious plan to build hundreds of miles of underground tunnels
06:20and corral London's lost underground rivers into a super sewer that would pump London's waste far out into the Thames estuary.
06:29The cost would be 4.2 million, over half a billion in modern money.
06:35But this was blocked by politicians who were worried about the cost.
06:41There needed to be a moment where people recognised that something had to be done.
06:461858. It's been about seven years, Bazalgette has been trying to get Parliament to give him the money to build the sewer system.
06:56And at this time the MPs are still very dismissive until this particular summer, because it was a hot summer.
07:03Basically the smell became completely unbearable and it actually started affecting the politicians.
07:10They had to shut down Parliament.
07:11So at this point Westminster decided, OK, we really need to do something about this.
07:18So finally, in June 1858 Parliament passed the Metropolis Management Amendment Bill, which provided finance for Bazalgette to start work on a sewage reform.
07:33Today, London again needs to wage war on waste as the old system faces new pressures.
07:42Bazalgette put a lot of forward thinking into the design of his system.
07:45So even though there were only about 2 million people in London at the time, he designed for about double that.
07:52But what he didn't anticipate is that the population of London would actually reach closer to 9 million within about 150 years of his system being built.
07:59And so a new super sewer is about to be born.
08:06It's a project as ambitious and groundbreaking as Joseph Bazalgette's original creation.
08:13Tideway.
08:14Tideway.
08:16A brand new mega tunnel running 25 kilometres from Acton in West London to Stratford in the east.
08:25This is one of the biggest infrastructure projects since the London Underground.
08:30It will relieve pressure from the system and help clean up the river.
08:34The super sewer will be drilled beneath the city by six gigantic tunnel boring machines.
08:45Their job is to bore a hole nine metres across that runs almost the whole length of London.
08:51These drills are so vast it's difficult to transport them by road or rail.
09:02July 2020.
09:05One of these massive drills glides majestically up the Thames.
09:08This is a state of the art tunnel boring machine built in Germany at the cost of 15 million pounds.
09:21Now she has crossed the channel to be delivered by barge to Chambers Wharf in Bermondsey.
09:33Today's a really special day. It's taken a lot of people a lot of time to plan this operation.
09:39This is the culmination of many years worth of planning and a lot of hard work by Tideway.
09:42This dirty great drill is being transported on a hydraulic barge called Skylift 3000.
09:56This is a jack up barge, it can lift 3,000 tonnes.
10:01It weighs the same as 300,000 bricks.
10:06This TBM weighs around 900 tonnes with its cradle.
10:09It's just under nine metres diameter.
10:16When it gets to Chambers Wharf, Skylift will anchor itself next to the cofferdome on massive hydraulic legs.
10:24Tomorrow morning we'll be repositioning the barge between the gantry crane structure that you can see there.
10:30We'll then jack up and assemble a ramp and then we'll take the TBM off the barge.
10:34From there, she will be lowered more than 30 metres below the ground.
10:40We will start tunnelling our five and a half kilometre journey to Abbey Mills.
10:47She will be boring a stretch of the new super sewer, which links the whole system to the pumping station at Abbey Mills.
10:54Another of this super sewer's tunnel boring machines, or TBMs, is about to start work further west at Frogmore.
11:04So today Charlotte has arrived on site. All TBMs have female names and ours is called Charlotte.
11:14She's named after the suffragette, Charlotte Despard, who helped found the Women's Freedom League in 1907.
11:21Jennifer Eyre is a shift engineer on the Frogmore Tunnel section of the project.
11:27This is my first tunnelling project that I've been on.
11:30But this is not Charlotte's first rodeo.
11:33So one of the things special about Charlotte is she's actually 26 years old, has done multiple other tunnelling projects,
11:39and this is her last project before retirement.
11:41She will be lowered into the tunnel by a 500 tonne crane. Her last job isn't going to be easy.
11:48She'll have to bore a three quarters of a mile long tunnel from King George's Park to Carnworth Road on the other side of the Thames.
11:56Charlotte is actually the smallest TBM on the project.
12:00Even so, she's more than 70 metres long, constructed in multiple segments.
12:06This is a model of a typical tunnel boring machine.
12:08Right at the front, you can see the cutter head. In the middle is the nose cone.
12:12That's the first thing that will touch the muck in front of the machine.
12:15This rotates, and as it rotates, it clogs up this area with muck.
12:20That means that you can keep the pressure in the face, which means that the ground in front of the machine doesn't collapse.
12:25As it rotates, there's a screw, an Archimedes screw mechanism that also rotates,
12:30and the muck is kind of sucked up into the machine to the back of the screw.
12:33It's then dropped onto the conveyor belt, and the conveyor belt takes it to the back of the machine,
12:39where a train with muck skips will be waiting to take the muck away.
12:42She's going to do two drives from here, one about 500 metres to our sister's site at King George's Park,
12:52and the other about 600 metres towards Carnworth Road, where it'll link up to the main tunnel.
12:56The tunnel will be bored 30 metres beneath the bustling streets above.
13:04One of the fun things about working underground is that you're completely invisible to the public above you.
13:10So right now, I don't know if you can see, but we're in this massive hole in the ground,
13:14but all that's above ground is a big grey shed.
13:16The residents came around the other week, had absolutely no idea that this massive cavern was underground 20 metres from where they lived.
13:25If Charlotte can make her final journey, the river will be spared a deluge of sewage next time London gets a downpour.
13:33It's early morning in the London borough of Hounslow.
13:44A team from on-site are here to fit new technology to the Victorian sewer system.
13:51Busy area, a lot of sewers, a lot of problems. One, two, three.
13:56We're in Hounslow today, and we've had round about 3,000 blockages here in the last 12 months.
14:04Blockages are one of the biggest issues that we've got on our sewer network,
14:08and we are really utilising all the latest technology in order to combat that.
14:13Sean Arnold and Wayne McClory are part of Thames Water's monitor installation team.
14:19They're fitting an ingenious gadget which will help to detect blockages in the system.
14:24This year we'll be installing 5,000 sewer level monitors.
14:29Is the channel all clear, is it?
14:31Yeah.
14:32What that allows us to do is get a monitored network, so it will give us warning when blockages start to form.
14:38The plan is to install the sensor as close as the exit pipe as we can.
14:43But we know we need the sensor power.
14:46We will then set the alarm, so as soon as the channel has reached its capacity,
14:49we will then send an alarm to Thames to notify them.
14:54The sensor fires an ultrasonic beam into the pipe.
14:59If the flow rises above an acceptable level, it triggers the alarm.
15:03The hourly flow rate of the pipe is constantly recorded on a logger, fitted inside the pipe.
15:08The whole system is linked to a computer, using mobile technology.
15:14Within the logger, there's a SIM card, and then we then attach an aerial.
15:18This can be fitted as close, as high as the chamber is required as you can imagine.
15:24Go into a tunnel, there's no signal on your mobile phone.
15:27The exact same with this.
15:30It's definitely a positive step forward, definitely.
15:34So what we're going to do now with Wayne, I'm going to ask him for some measurements,
15:38so we can calibrate the system, so make sure everything's on point before we leave.
15:4330mm of flow.
15:4530mm, okay.
15:47And total overhead.
15:49Which is the total height, yeah.
15:511760.
15:52So we can see here it's reading 32mm, with good pings, 8 out of 8.
15:58It's reading good, it's bouncing off the flow, it's coming back up great.
16:0232mm is perfect, so I can go ahead and stop the measurement and set the alarm.
16:10All done.
16:13Which way are you going?
16:15Straight up.
16:16The information from the monitors is sent to the Proactive Control Centre at Reading HQ,
16:27where analysts turn the raw data into information they can act on.
16:32What it shows here is the entire Thames water catchment area,
16:36and within that are individual sewer depth monitors.
16:40On the computerised system, known as SLAM, Daniel can monitor a massive area of London.
16:48This is telling us that something has come into the system and really overloaded it,
16:52and this could be a potential blockage that we need to investigate,
16:55due to the fact of how high it stayed above alarm level.
16:57We have a spike in our system, and that is rainfall,
17:00so this wouldn't necessarily mean that there's a blockage in the system,
17:03it just means we've had lots of rainfall come in, and it's quickly flushed out of the system.
17:06Where we would look is this area here, where you get a sudden increase in the depth recorded off the monitor.
17:13Now, the fact that this isn't alongside any rainfall makes it very likely that there's a blockage in this area.
17:20The blockage is in the Victorian sewer in Hammersmith.
17:23A team from Lanes Group, who maintain the sewers, are sent out to investigate.
17:28We're here today to tackle the biggest siltberg that we've actually come across in my time as working for the Davis Thames.
17:37Siltbergs are huge build-ups of mud and sand that have been swept down the drains.
17:45This one is over a metre wide.
17:47If you get a flash flood at some other point in London, this is where it's going to end up.
17:53It will affect the pumping station down the road, and it will affect the public at some point if we don't deal with it.
17:59Andrew Howard is an engineer in charge of clearing sewer blockages.
18:03He and his team work the night shift.
18:05We don't know what's beyond that, so if that's blocked, the sewer system will then become blocked and it will then start flooding all over London.
18:17Louis and Wayne have to go down into the tunnels to remove the siltberg.
18:21They sweep it towards a machine that works like a giant vacuum cleaner, pumping the waste out of the tunnel.
18:28It's a hostile environment. You're in a confined space.
18:31The actual barometric pressure is different. You've got danger of moving solids, you've got danger of flooding and drowning.
18:40All these aspects have to be taken into consideration.
18:43You've got two guys here at 22 degrees, which doesn't sound much, but when you're working away shoveling, it's like working in Blazing Sunshine.
18:52You can only do so much for so long.
18:54In Victorian times, Baseljet sewer builders had to contend with all these hazards and more.
19:03These men were known as navvies and they were the physical muscle that built the modern age.
19:08So navvies are what we would call unskilled manual workers.
19:14Very often Irish immigrants and people who come in from the countryside.
19:19These guys built the entirety of British industry. They built the canals, they built the sewerage systems, they allowed the 19th century industrial revolution to happen.
19:30They were incredibly hard-working and incredibly overworked.
19:36Baseljet worked his navvies hard, but he made sure the public knew these men were doing an incredible job, in often terrible circumstances.
19:45One interesting aspect of Baseljet's project was that the navvies were not represented, as they were usually, as a crowd of uncouth workers, but they were presented to the general public as heroic, as people who were in fact working for the public good.
20:05The way in which these sewers are built is using a method that we would now call cut and cover, which is exactly what it sounds like.
20:16Cut into the ground, so you dig down from ground level, you create a trench, you line it up with bricks, you put a cover on top of it, and then you go and put the ground back on top of it after that.
20:26And it's almost impossible now to imagine what that would have been like with any degree of accuracy, to be doing this with spades, with pickaxes, by hand, propping it up by hand with wooden trusses and the wooden beams that you've got, lit by candles and by very inadequate forms of safety lamp.
20:51A nightmarish job made all the more terrifying by the knowledge that the whole of London was above you, waiting to fall in.
21:00At Hammersmith, Andrew and his team have made good progress.
21:05There will come a point when it will end, where, I can't tell you at this precise moment in time, but we'll just keep going until we get it out.
21:2130 metres beneath the busy streets of Wandsworth, TBM Charlotte worms her way towards King George's Park.
21:30She is boring what's known as the Frogmore Connection Tunnel, which will link the existing sewers south of the Thames with the new super sewer at Carnworth Road.
21:39So this tunnel is capturing all the wastewater from the ones of town area, so it will be capturing all the waste from the Frogmore Connection Tunnel and it will divert and get down into Carnworth Road.
21:50To do this, Charlotte must grind metre by metre through the compacted mud, known as London clay.
21:57It's good because it's not very waterlogged, but also it keeps its shape so it doesn't completely collapse, so something like sand is a lot more difficult to tunnel through.
22:10But London has over 3 million miles of subterranean cables, as well as 112 miles of underground train tunnels beneath its streets.
22:20Steering the drill to avoid obstacles is no easy task.
22:24This is where the driver stands when he's driving the machine. These are all kind of propulsion levers and he can see all the information he needs on this screen here.
22:34And the navigation system is behind here as well.
22:38The system uses laser triangulation to keep the TBM on target.
22:44For navigation, we would drill prisms into the lining that we'd already placed.
22:48And from that, we could use a computer at the front of the machine that would be able to point a laser at these prisms and be able to know from the angle it was coming in and the intensity of the laser exactly where it was relative to that computer.
23:05When I started working in tunneling, I was actually quite surprised by how precise it was.
23:08So our tunnel is about a 3.3 metre excavation radius, but we had to be precise to 30 millimetres and normally we were within about 10 mil of the exact location of where we're supposed to be.
23:23Precision was also incredibly important in Victorian times.
23:27The extent of Bazalgette's plans were enormous.
23:31He actually went down into the bowels of the earth into the London sewers and surveyed the sewage system as it then was.
23:42He was a man who really knew stuff from the bottom up.
23:47Bazalgette made repeated visits to the dangerous tunnels himself.
23:50He insisted on going down in person as the sewer success depended on the minutest calculations.
23:58What Bazalgette sought to do was to create a unified system and it was a unified system in which drains led into sewers and sewers led into massive outfall pipes.
24:11The whole system uses gravity to keep the sewage flowing.
24:14One of the important design features of a sewage system is the gradient or the slope of the sewers themselves.
24:22It's a tremendous problem to enable this system to operate without artificial forms of pumping. It has to rely upon gravity.
24:31So he calculated that every mile the sewers would go down exactly two foot and this way everything flows at the same rate and you don't get any flooding occurring.
24:40It was a unified system which then took the sewerage and the rainwater and all the effluent down to great pumping stations which would remove the problem.
24:50Abbey Mills pumping station is a cathedral of sewage.
25:01Bazalgette's tunnels may have been invisible but his pumping stations were designed to be seen by his London donors.
25:08What's really amazing about the whole sewer system for me is the pumping stations because these are the largest steam engines in the world at this point and this is the Victorian era. Steam engines are big. These are enormous but also they're decorated to look like they're neoclassical. They look like sort of Greek palaces.
25:32So these pumping stations are serving two purposes. One is eminently practical. It's about taking all the stuff of the sewers out of the sewers and away from London.
25:47They serve an almost equally important purpose which is propaganda as much as anything else.
25:52Well they're beautiful buildings you know walking past and they go well that's where my money went look at that that's incredible.
25:59And the reason for that was that the people of London has spent a fortune their rates have gone up. You know this has been a very unpopular very invasive engineering project and they've got nothing to show for it.
26:09It's all underground except these pumping houses which look beautiful.
26:16They are cathedrals is how they're described at the time.
26:20Over the years the Victorian steam pumps have been replaced by electrical ones as Abbey Mills has expanded to keep up with demand.
26:28There's a fuse missing but I don't believe that's the issue.
26:31That shouldn't be because it's not connecting.
26:33Dan and Ash are electricians working for Thames Water. They've been sent to Abbey Mills to fix a problem with the pumps.
26:41Yeah it's the hydraulic flushing pump. They said it kept tripping so just testing all the fuses making sure that none of them are blind.
26:51Looking for any obvious errors before we start taking things apart.
26:55Abbey Mills is on the River Lee in East London which in 1868 was right on the edge of the city.
27:02So the water comes in from West London all the way to East London and the inlet pipe is another 20 or 30 feet down below us.
27:10All we do in Abbey Mills pumping station is lift the floor.
27:14The way this works is it just pumps the water up and then it uses gravity to flow to its next destination.
27:21So how does it look?
27:22Everything's good. All the fuses, the ones that are in are working and all the relays are healthy. No problems that are continuing.
27:30Well that's good news.
27:31Abbey Mills originally started off as just a station which we're in now which was just eight pumps.
27:37But because of the growing demand it now has an additional five stations and 30 plus pumps that you had to get more stations in because it couldn't deal with all of the flow that it had to deal with.
27:50But 21st century pressures mean even the new electrical pump system sometimes struggles to cope.
27:57When it rains a lot, you know, a lot of things tend to get pushed to the limits. So when it rains that's when you tend to get more,
28:05we wouldn't say problems but, you know, things might be overworked so they might trip and then you've got to go reset.
28:12Yeah, that looks good. Let's move on. On to the next one.
28:16Back in Wandsworth, deep beneath the surface, Tideway's engineers are making good progress.
28:29These are concrete segments and in this tunnel every ring is built up of six of these.
28:35But when you bore a tunnel under the Thames, you have to keep the water out.
28:40Engineer Isambard Kingdom Brunel lost six men when the river flooded into his half-built Thames tunnel in 1828.
28:48Today, Tideway take no chances.
28:52All the concrete segments that we need for a ring will come up with the muck skips.
28:57They're in two piles of three.
29:00The segments are manufactured on the Isle of Grain in Kent and transported by barge up the Thames.
29:06We had a sort of segment hoist arm, a bit of a robotic arm essentially,
29:10that was controlled by levers by the TBN driver.
29:16So he'd manoeuvre it to pick up a segment and then it would rotate into the position that we wanted it around
29:22and would place the segment against the lining that we'd excavated.
29:27The typical sequence during a shift is you'll dig a meter and in that meter some rams will extend it at the front.
29:36So there's a void that you then fill with concrete segments.
29:40And as you fill the segments, the rams contract and then you can push off of the ring that you've just installed.
29:46And that's how we keep digging the tunnel and making it longer.
29:50Working on a tunnel boring machine, you've got electricity, so you've got lighting.
29:55You also are encased in a metal cylinder and so you're not really too worried about leaks coming through the ground or any sort of collapses.
30:04And that's something that the miners back in the Victorian times would have had to deal with every day.
30:10I can't imagine what it would have been like working on the original London sewer system in the 1860s.
30:16Yeah, I think tunnelling back in the Victorian times would have been very dirty, very mucky, a lot less safe than it is now.
30:22That's the last one, no more nails.
30:27Joseph Bazalgette didn't have prefabricated concrete segments to line his tunnels.
30:32He had to make do with bricks.
30:35380 million bricks line his tunnel walls.
30:40Bazalgette used brick to line his sewers because that was one of the most used materials of the time.
30:45And it was easy and quick to produce, to transport to London.
30:49Brick is a conventional form of lining for water, but they have a particular advantage in the sewers,
31:00which is that unlike pipes, unlike ceramics, unlike in fact some forms of cement, bricks could also move.
31:11The real risk behind running pipes under London is that they crack,
31:16that they don't cope with the force of the earth and the force of the movement around them.
31:21Bricks provide strength, they provide endurance, but they also provide movement.
31:27And that movement is critical to the enduring ability of the sewers to function.
31:33But actually they survived far longer and far better than he ever thought.
31:38And that's because the human effluent that goes through the sewers gets into the bricks because they're porous.
31:44And it actually strengthens the bricks.
31:47So now we have double strong Victorian sewage bricks, mainly thanks to, well, Victorian poo.
31:55And to make his tunnels as waterproof as possible, Basil Jett used a revolutionary new material.
32:04Basil Jett decided to use Portland cement, which was a relatively new material.
32:08It was advised very strongly not to use Portland cement.
32:12It was too new. They feared that it might be too hard, that it might crack,
32:16that it might not be able to withstand the pressure that had been put on.
32:20I personally think it was quite a risky decision to make.
32:24Because Portland cement is strong and is so hard,
32:27which means that it might be prone to cracking.
32:30Basil Jett knew that.
32:31And so what he does is to develop a form of what we'd now call quality control,
32:36in which he has people inspecting every batch of the thing
32:40to make sure that it is exactly what is ordered.
32:44He needed to make sure that his mix was in exactly the right proportions everywhere.
32:49Basil Jett stuck to his instincts, and he proved to be absolutely right.
32:54Portland cement lasted, it worked, and indeed it's now the form of artificial stain
32:59that's most widely used in the building industry.
33:02It's early morning in Hammersmith, West London.
33:16One of the biggest moments in the Tideway project is underway,
33:21linking Basil Jett's old sewer to the modern tunnels below.
33:26But Hammersmith has a particular problem with sewage.
33:29This actually has one of the biggest catchment areas on the whole of Tideway project.
33:35Hence we have the biggest storm flow rate here to deal with,
33:39which is where all the storm water and sewage comes from.
33:42Basil Jett designed his sewer so that if there was a storm,
33:45the sewage would overflow into the Thames.
33:48In 2016 alone, sewage emptied into the Thames through these overflows 50 times,
33:55far more than Basil Jett envisaged.
33:57So the principle of the project is to redirect those overflows
34:02and direct them into the new Thames Tideway tunnel.
34:05But Will Thorpe and his team face a challenge.
34:11The fast falling sewage will drop 15 metres to get from the Victorian sewer
34:16to the new Tideway tunnel.
34:18We are dumping the equivalent weight of 8,500 blue whales per week of raw sewage
34:27and the Tideway is there to collect that.
34:29So each week it is going to be taking a huge amount of sewage
34:33from the Basil Jett system into the new tunnels
34:36and that amount of liquid needs to drop vertically
34:40and therefore quite dramatically over quite short distances.
34:45You don't really think about it, but moving water can create absolutely humongous forces.
34:51So if you think about waterfalls where water is flowing along constantly,
34:56it's eroding rock and stone.
34:59That means the liquids flowing from Basil Jett system into Tideway
35:03are going to cause that pounding effect on the materials in Tideway
35:07and so it's inevitable that it will start to wear away.
35:14Hammersmith Pumping Station has the largest design flows
35:18out of all the other Tideway sites.
35:21At peak storm level it will be 42 metres cubed per second of flows.
35:26To prevent that from wearing the shaft away,
35:28Will is part of the team installing a vortex tube.
35:32This huge structure behind us here is the Hammersmith shaft vortex tube.
35:37This weighs approximately 65 tonnes
35:40and this is what is going to be sat inside our shaft
35:43and will generate the vortex of flows down into the tunnel.
35:48So the main purpose of the vortex tube is to help force all the flows
35:53into a vortex swirl down the tube itself.
35:56The tube makes water spin rather than gush as it descends.
36:00Within the vortex, instead of this water pounding down and hitting the floor
36:07again and again and again until the floor is obliterated,
36:12instead the water descends down like the water in a plug hole until it slides.
36:19This means that the water is actually almost sliding against the sides of the tunnel
36:26rather than pounding straight into it.
36:28And in that way doesn't cause nearly, not even a fraction of the damage
36:35that the simple process of a waterfall actually would.
36:38The vortex tube is 20 metres long.
36:43The vortex tube is sat here now waiting to be lifted into the shaft.
36:47That shaft is 30 metres deep and in places it's only 11 metres wide.
36:53Will and the team must drop the tube down without scraping against the walls
37:00or damaging the ends.
37:02It's a mammoth task.
37:05So yeah, absolutely huge day today.
37:08A huge amount of preparation and work has been done leading up to this
37:12in order to bring all this together.
37:14In order to lift the vortex tube into the shaft safely,
37:17we are hiring a 750 tonne mobile crane
37:20and we will be lifting the vortex tube from one end
37:24whilst it pivots around the foot using a special boot.
37:27The process is done in stages, one step at a time.
37:33At each individual step, the engineers must go up in a cherry picker
37:37to readjust the bolts holding the lifting harness in place,
37:41then lift the tube another step of the way.
37:44Spent a few hours getting to this position.
37:47Probably be a couple more hours to get it to vertical
37:49and obviously once we've got it to vertical
37:51then we can lift it into the shaft.
37:54But before they can lower the tube into the shaft,
37:58they have to turn it 180 degrees.
38:02It's a delicate operation.
38:05So we'll be releasing it from the table soon
38:08and lifting it over the shaft.
38:14A little bit nervous.
38:15Obviously a lot is riding on this at the moment
38:17but we're confident that we've got it in hand.
38:20Finally, the vortex tube is manoeuvred into position over the hole
38:25and lowered gently into place.
38:31Yeah, so now the vortex tube is in.
38:33We'll be encasing the vortex tube in concrete.
38:35The whole project is designed for 120 years.
38:39That's the minimum time that it's been designed to be in the ground for.
38:42So a brilliant time today to see this going in,
38:46to be there for that amount of time.
38:49It'll protect Londoners from the ravages of raw sewage,
38:52just as Basil Jet sewer did 160 years ago.
38:56The improved sewage system all but eliminated colour in London.
39:00Ironically, Basil Jet himself was a miasma theorist.
39:05He believed that it was things that floated through the air
39:08from decaying fetid material caused illness.
39:12And he believed that if you could keep the smell from getting to people,
39:16then these airborne diseases would come to an end.
39:19Of course he was completely wrong.
39:21In fact, it was actually the water itself that was causing the problem.
39:25But in order to get rid of the smell, he had to clean the water.
39:28And by cleaning the water and getting the sewage out of London safely,
39:32he saved tens of thousands of Londoners' lives.
39:36Six months after she was lowered into the ground,
39:40tunnel boring machine Charlotte is about to reach her first destination,
39:45the access shaft at King George's Park.
39:48We started breaking through around half eight this morning.
39:51It's taken about four hours to get through the two rings.
39:53It's about 400 mil of shock creep.
39:57Choking clouds of dust are a perennial problem for the engineers,
40:02as the TBM churns up the earth.
40:06The cutter head of the TBM has different types of teeth on it
40:09to help excavate the muck.
40:11We've got rippers around the edge.
40:13We've got scrapers to the middle.
40:15And you can see there's a bit jutting out in the middle.
40:17That's the nose cone.
40:19When it's breaking through, you get a lot of dust generating
40:22from when it comes into contact with the shock creep.
40:24So we have a mist curtain installed,
40:26as well as the good old man on the nozzle.
40:29So that'll be just to suppress the dust when it comes out the shaft.
40:32It's rainy, pretty wet.
40:34In a way, that's kind of nice,
40:35because it's meant there's not been so much dust kind of around the shaft.
40:38But I guess when you're mucking through clay, it doesn't matter.
40:41It's sunny or rainy.
40:42We're just glad that we've come to the end.
40:47Finally, Charlotte breaks through.
40:50It's a significant milestone in the Tideway project.
40:54This is the first breakthrough on Tideway across the whole project,
40:57not just the west.
40:59It's so exciting to get to the stage,
41:01because it means our first drive is complete.
41:03So we could theoretically, you know,
41:05go down the shaft in Dorme Street,
41:07walk 500 metres and pop out at a completely different location.
41:12A few weeks later,
41:13Jennifer is able to return to the finished tunnel to inspect the result.
41:18We finished the primary lining
41:20and we've done a secondary lining layer
41:22that's about 150 millimetres thick.
41:24It's to help with waterproofing and ensuring the design life,
41:28everything's designed to on Tideway.
41:31It's taken a long time to get to this point.
41:35It was about two and a half years
41:36from first digging the shaft to get down to the tunnel
41:39and then completing the secondary lining.
41:41It's really great to see it finished
41:44to show that we are that much closer to our goal
41:47of cleaning up London's River
41:48and really making a difference to London.
41:51Lots of my friends sort of joke to me
41:55that I'm working on a poo tunnel,
41:56but as you can see it's nice and clean at the moment.
41:59Once it's been commissioned, handed over to Thames Water,
42:02it'll be anything but.
42:03We'll have sewage flowing down it
42:06and it will not be somewhere you want to be.
42:09But just being here right now
42:11gives Jennifer a real sense of pride.
42:16I love coming down to the tunnel
42:17and seeing the completed product
42:18and so it's so nice to be able to see something
42:20that I've been able to contribute to
42:22and that I can tangibly see.
42:24Her work and that of all her colleagues,
42:27both at Tideway and Thames Water,
42:29will keep London's sewers running safely
42:32for decades to come.
42:35London's an ever-growing city,
42:37so you can only imagine that the demand
42:39for this tunnel will only be greater and greater.
42:41and so it'll be more likely to be more full more often
42:45in 50 years time than it is now.
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43:08Transcription by CastingWords