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London Underground: the River Fleet

Day 1 in London, November 14, ----, 3:30pm local time.
         Ah! London! Sewers!
         I’m sitting right now in a Starbucks in central London, where I popped in to use the bathroom and hang out for a few hours while I wait for my friend to finish work. As I flushed the toilet, it occurred to me that I might see those same turds again in a few hours. Tonight we’re going to visit part of London’s sewer system: the River Fleet, a tributary of the Thames that flowed through central London until it was put underground—and connected to the sewer system— in the 19th century.
         I just arrived in London a few hours ago, flying in from New York. My friend and exploring partner goes by the cryptic name of DS. I met him at his office and dropped off my bags of gear– chest-high rubber waders, gloves, camera, tripod, flashlights, headlamps, spotlights (for light-painting photos), an air meter, even an inflatable inner tube for a possible rafting trip along an underground river in Northern England.
Day 2 in London, November 15, ----, 7am local time.
         Was in the River Fleet last night and into this morning. Just got back to DS’s place. I want to tell the story of our night, but I think I have to start with the river itself:
         THE RIVER FLEET flows from two underground springs in northern London, in Hampstead Heath (a large park on the North-western part of the city) on each side of Parliament hill. The western source starts at the Hampstead Ponds, and the old course of the river just to the south is marked by Fleet Road. The second source is in the northern edge of the park, on the grounds of Kenwood House. A longer series of ponds, the Highgate ponds, show where this spring flows along the eastern side of the park.
         The two springs unite just north of Camden Town. In 1826, it was recorded that the river at this point was 65 feet wide. The Fleet had always one of London’s bigger rivers—the name itself is thought to have been derived from a word meaning, basically, “big enough to float a large boat”—but by the 19th century it was deeply polluted, serving as a drain and sewer for the entire area.
         This was going to be my first time into the London underground. DS and I met with another urban explorer, who goes by the nickname Loops. The manhole that was our goal was a square hatch in the middle of the sidewalk, next to a stoplight on a busy street. It was well after dark on a weeknight, but people walked by constantly. Some were headed toward the hotel just down the street; others were simply walking. At one point when the coast seemed clear, a couple came meandering along the sidewalk. They were obviously and enthusiastically on a date. They held hands and lingered, leaning into each other and stealing a quick kiss. They were moving at a snail’s pace. A dozen feet from the hatch, they stopped completely and admired the ornate stone building next to us. We had already put our rubber waders on, and we sat on a low wall across the street and tried to look inconspicuous in the rubber suits. Finally the sidewalk was empty. We walked over, as quickly as possible in the rubber waders. As DS and I stood casually, Loops knelt down to try to undo the latch that normally prevents anyone from opening these hatches from the top.
         We were here at this relatively early hour because of the tide. The Thames is an estuary in which high tide rises more than twenty feet above low tide. I don’t know how that’s possible; I think it’s because water flowing down the river hits the incoming tide, and the conflux creates tides much higher than I’ve seen on the east coast of the US. But because of this, the final portion of the Fleet is completely flooded from mid-tide onward.
         The hatch was what DS called an “easy-lift.” The hinged square cover was far easier to raise than a heavy manhole—at least, once it was unlatched. Loops was still struggling with it, his headlamp on now. DS bent down to help him. Eventually he threw down the tool he’d been using, and with one finger jammed through the tiny hole he was able to jimmy the latch. We raised the hatch, and then the heavy grill just beneath it.
         I went down the ladder into a small, dry brick tunnel. DS was just behind me. From the bottom of the ladder I looked up: a small square view of the night sky, and then it disappeared as Loops lowered the grate and the hatch cover. In the sudden darkness, the scrape and clang of the metal grating echoed ominously off the Victorian-era brickwork around us. But we were in! I was elated.
         It’s the incredible brickwork that makes the London underground so amazing. The sewer system was constructed under the engineer Bazalgette, who researched and planned in the 1850s and started construction of the hundreds of kilometers of brick tunnels in the 1850s. Thousands of workers dug tunnels and laid brick and stone to make the sewers for the rich and burgeoning metropolis.
         Although few ever saw it, Bazalgett’s sewer system was one of the engineering marvels of its day. Round brick tunnels ranging from six to twelve feet in diameter hold mainline sewers, as well as rivers like the Fleet that had become so polluted that they were best put underground. Round tunnels flow into even vaster tunnels shaped like an upside-down horseshoe, with gently concave floors. Smaller channels were often oval or egg-shaped. (With the smaller end of the egg’s profile pointed downward, this shape keeps sewage flowing faster even when it’s low flow, and that helps reduce silt build-up.)
         These were built not only for sewage and wastewater, but also to drain the city of rain or snowmelt. Because of this, the tunnels often seem needlessly huge. In most of the Fleet, the tunnels range from eight feet up to twenty feet high. The flow of sewage and water we encountered, however, was rarely more than one or two feet high. But in heavy rains these tunnels could fill up almost completely. In manhole shafts, markers ran up the sides with markings every meter, showing that the water could potentially rise much higher even than the top of the tunnel.
         When Bazalgette designed the sewer system, one of the most important things he did was create a system of five “interceptor” sewers, which ran parallel to the Thames at various distances and intercepted the water from the north- and south-flowing sewers to carry the sewage to a treatment plant. Previously, the sewage had flowed directly into the Thames, near where drinking water for the city was withdrawn. Bazalgette’s new system probably saved an incalculable number of lives from disease.
         But when it rains, the flow vastly increases. The rainwater mixes with the human sewage. The treatment plants and interceptor sewers are unable to handle the load. As the flood of water and sewage comes through the tunnel, it rises over the small diversion dams that normally direct it into the interceptors, and a flood of untreated sewage is released directly into the Thames.
         This is a problem common to almost every older city, and is one of the most serious public health issues for urban waterways. Cities try to deal with it in a variety of ways; London is beginning to work on a gigantic deep-underground tunnel which will serve as a reservoir or holding tank for excess sewage when it rains, which can then be slowly released and treated in dryer weather. It should be ready in about 2020. In the meantime, every time it rains, raw sewage is released with the rainwater into the Thames.
         Of course this is an imperfect system, but cities are organic growths that re-use and build on their past. Therefore almost nothing in an older city is going to be perfect, because the systems and infrastructure in use are so often leftover from an earlier period of growth. It’s imperfect, but nonetheless I love seeing the sort of cut-away view of both the history and the physical structure of a city that you get from seeing old underground systems in a modern city.
         Cities that are planned and built in the modern era—like many Australian cities-- always have separate storm drains systems (for rain) and sanitary sewage systems, so they can avoid this problem. But in a large city like London or New York, it’s basically impossible to add in a new separate system for stormwater. The cost is prohibitive and urban populations would never accept the city-wide shutdown that the construction would cause. But this highlights even more what an incredible thing Bazalgette did in constructing the system in the first place—perhaps the largest infrastructure project London has ever undertaken, a masterpiece of Victorian-era brick and stonework that is still fully in use today.
         The bricks inside the Fleet looked as if they had been laid just yesterday. Hard-fired dark bricks formed the floor, sometimes changing to large flagstones. As the tunnel changed shape and size, we could see that the arches were made with four, five, even six layers of bricks. I couldn’t believe the amount of work that had gone into this.
         When we first came in, the water was about two feet deep. Our manhole opened into a small network of access tunnels that led in one direction to the equipment that could raise or lower huge floodgates. Now the gears everything else was almost unrecognizable underneath a swollen, flaking layer of rust and a coating of black, oleaginous mud.
         In the other direction, the tunnel led us into a set of ladders and catwalks that led down into the main tunnel itself. It was incredible: near the outfall here, it was a giant chamber easily twenty feet high and equally wide. The exquisite brickwork vied for my attention with the sheer architectural wonder of it.
         Though most of the standing water near this of the Fleet’s tunnel seemed relatively clean, we quickly encountered sewage when we passed the interceptor tunnel a few hundred feet upstream. A steady stream of obvious sewage flowed into the interceptor, making a waterfall that roared and pounded in the confined space. A four-foot high dam stretched across the main tunnel of the Fleet to prevent it from flowing through the outfall and into the Thames. But it was clear that with even a little bit of rain the water level would rise enough to go over the dam, flowing into the Fleet tunnel and then into the Thames.
         I had on chest-high waders, and was glad of it. Loops and DS both just had hip waders, essentially crotch-high boots. They were easier to move in than my rubber suit, but it occurred to me that if I fell I’d probably be able to stay dry– but if they fell, the high boots would immediately fill with water. The slime that coated everything made it impossible to walk on the sides of the concave floor without slipping, so we trudged along the center. The water would only have been shin-high if it had been standing still, but with the heavy current it splashed past our knees.
         Wading through sewage is a nasty business. In purely sanitary sewers, the water is often a bilious green-brown. (“Sanitary sewers” is the official term for pipes that carry raw sewage, to distinguish them from the cleaner storm drain tunnels designed only to carry rainwater runoff.) In combined sewers, as were built in the Victorian era, street runoff often dilutes the sewage so that the smell is not so bad, and you can sometimes go many steps at a time without being reminded that you’re in a sewer. But the worst part of venturing into sewers is seeing something recognizable: tampons, condoms, maxi-pads, streamers of half-disintegrated toilet paper, or the occasional turd bobbing in the water. We saw all of these as we trudged upstream. The smell was bad, but not awful; only a little worse than I’ve smelled around pigsties or slaughterhouses.        
         But neither the smell nor the sight of floating turds could detract from the excitement I felt. This was the great Fleet River; it had been flowing along into the Thames since before the Romans first established Londinium. The intersection of the Fleet and the Thames was one of the reasons that London had become London, a great city built on a foundation of water-borne trade.
         After the great fire of London, Christopher Wren (the great architect behind St. Paul’s Cathedral) had designed at least one bridge over the Fleet, and I eagerly looked at the walls when the tunnel changed shape or size to see if I could tell where it had been integrated into the tunnel when the Fleet was put underground. I don’t know if I saw it, but what I did see was a palimpsest of London history from Victorian times to the present: old stone arches, Bazalgette’s amazing brickwork, flagstone floors in some tunnels, new sewer line connections of metal pipe, ancient sewer connections of brick tunnel that had been sealed up, because the building or possibly even the entire street that they had served no longer existed. Ancient, rusted ladders led to 19th-century manhole shafts capped by heavy iron covers. Newer ladders, visible in access rooms ten feet to the side of the main tunnel, led to stainless-steel hatches like the one we came in.
         Beyond all this I could see the ancient history of London. With a deepwater port on the estuary of the Thames, all that was needed for the growth of a great city was freshwater rivers. Some would be used for drinking water, others as canals to transport goods. The rivers could also be used for waterwheels to run mills—something the tidal Thames could not do. The Fleet and its companion rivers provided all of these things. And the city grew until it was the center of a world empire, and then it became so large that the small rivers that had fed it were now nothing more than impediments, loose threads in the urban fabric that blocked traffic and occupied valuable real estate. So the rivers were put underground, and as always happens in cities, history and the past were eaten up as the city built for the present and the future. Except that the past is still there– it’s just hidden away, and you have to work a little harder to see it.
         We were done by about 3:30am. We had almost let ourselves get trapped by the rising tide, and in the final section before our exit, the water was so high that it came over the tops of Loops’ waist-high boots. The rising tide made it impossible for us to visit the southernmost section of the river tunnel, even though our exit manhole was so close to it. We would come back the next week at low tide to see the impressive outfall space, a gigantic brick-arched chamber with massive iron doors hanging at one end to serve as one-way valves for the water.
         We stayed in the access tunnels a little longer, wiping down our muddy, sewage-covered gear and packing up for a quick exit out the manhole. Even in that short time, we could see the tide visibly rise in the tunnel near the outfall.
         When we got out DS walked to his office, where he would wash in the bathroom and sleep a few hours on the couch before he had to wake up for his day job. I walked to the nearest Tube station, and had to wait two hours outside the station for the mornings first train. It was absolutely freezing as I waited, especially in my wet clothes, and I sort of wished I was back underground where it’s always warm.


  1. Awesome. London has an amazing history buried beneath, and this shows just a small part of it's depths. Great work.

  2. Absolutely fascinating! I wish I had the opportunity to see it for myself.

  3. This looks amazing. What an adventure...

    Do you know who best to contact to get access to the sewers? We're making a film and want to use this for a scene. Any help is appreciated.


  4. Excellent article historic and extremely interesting. Well done with you physical effort there.

    Thanks including photos

  5. I am currently undertaking a theoretical architecture project near Blackfriars bridge, of course near the site of the Fleet. Are you able to supply contact information so we can touch base?

  6. I would love to get involved with you guys at some point it sounds incredible. I've only viewed the sewers from above and outside so far. If you could put me in contact my email should be starched to this comment.

  7. This comment has been removed by the author.

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