Sewers of London
There were many great works of spectacular engineering
in the 19th century such as gigantic steamships, innovative
bridges and fantastic buildings. None of them, however, saved
as many lives as this immense and complex infrastructure project
under the streets of one of the largest cities of the world:
The Sewers of London.
It was 1854 and John Snow, a physician with his
practice in the Soho part of London, poured over his map of
the city. He'd been working on it since the first signs of a
cholera outbreak that year. Carefully he had marked where each
new case had appeared.
Dates: 1858 - 1870.
Engineer: Joseph Bazalgette.
450 miles (720km) of main sewers fed by 13,000 miles
(21,000km) of local sewers.
of: Brick and Portland Cement.
Victoria Embankment July 25th, 1870.
Drains depend mostly on gravity, with pumping stations
at certain locations.
318 million bricks were used in building the interceptor
Cholera was the scourge of big cities in the 19th
century and an outbreak could kill hundreds or thousands of
people. The prevailing notion was that the infectious agent
was carried through the air by smell, an idea called the "miasma
theory." Snow suspected, however, that the disease was actually
transmitted in some other way. In 1849 he'd written an essay,
On the Mode of Communication of Cholera, suggesting that
transmission was being made through unclean water.
His map seemed to bear out his idea. He found
by looking at his records that all the recent cases clustered
around a public water pump on Broad Street. Of those few cases
that occurred nearer to another pump he found that the residents
were still using the Broad Street pump anyway because they preferred
the taste of the water. Especially telling was that of the 70
workers at a nearby brewery, none of them got sick. They only
drank the beer provided to them for free. His study of the pattern
of infection was so thorough that he managed to convince the
local council to remove the handle from the pump, bringing the
outbreak to a close.
Still, his ideas would not be generally accepted
until after his death in 1858.
Fortunately, a project that would effectively
solve the cholera problem in London was already underway by
then, though the builders were mistaken in their beliefs about
the source of the infection.
Great Stink of 1858
Engineer Joseph Bazalgette.
Plans for updating the London sewage system had
been in the works for years, but it wasn't until the "Great
Stink" of 1858, that politicians were spurred forward to find
the money to put the project in motion.
Getting rid of raw sewage in a city as large as
London had always been a problem. Originally, cesspools - stone-lined
pits - had been used to contain human excrement. Often these
were built right below the residence. As they filled up, these
pits would have to be cleaned out every few years. As London
grew to having nearly 200,000 cesspits, it started to be impossible
to clean them all as often as they needed. Instead, they were
eventually connected to London's existing sewers so that the
effluent could be carried away that way.
These existing sewers, however, were storm drains
not designed to handle human excrement. They were actually natural
creeks and streams that had been covered over and thier contents
deposited directly into the Thames River. The additon of sewage
to these drains soon caused the shoreline of the river to be
piled with untreated human waste and industrial effluent. When
a severe heat wave hit the city in July and August of 1858,
the smell from the river became unbearable. The stink, coupled
with the idea that smell could carry infection, finally persuaded
authorities to do something.
Civil engineer Joseph Bazalgette had been thinking
about what to do about the London sewer system for many years.
In 1849 he was hired by the Metropolitan Sewers Commission and
one of his first jobs was to familiarize himself with the system.
He realized it was a mess. There was no great plan or standardization
to how the tunnels were built or connected. There was also no
end of ideas on how to fix the system, but they were all expensive.
Making things worse, the Commission was ensnarled in bureaucratic
red tape and disagreements on how to proceed, so little progress
physician John Snow.
In 1856, however, The Metropolitan Board of Works
took over for the Commission and promoted Bazalgette to chief
engineer, giving him the responsibility to come up with a workable
plan. His design was to create a set of massive drains that
would intercept the existing sewers before they reached the
river and carry sewage to a location east and outside of the
city where it could be released safely downstream into the outgoing
tide. These five tunnels, which were called "interceptor sewers,"
would be built along the path of the river, three to the north
of the Thames and two on the south side. In some places where
they ran along the river, these huge pipes would be hidden in
massive embankments on either side of the waterway.
To make sure the material flowed through the drains
easily Bazalgette decided the tunnels should fall at least two
feet per every mile. Since the Thames only fell 3 inches per
mile, this meant that pumping stations would have to be built
at intervals along the path to raise the contents of the sewer
so that the drains did not run under the level of the river.
It wasn't until 1858, when the horribly, odorous
fumes began coming out of the river, that £3 million was authorized
by Parliament to address the problem. The work started with
the three northern sewers. The easiest way of building them
was the "cut and cover" method. Workers would first dig a trench
the width and depth of the tunnel and then the brickwork of
the sewer would be built inside. To get the maximum strength,
the drain was designed with an oval cross section similar to
that of an egg. After the tunnel was finished, dirt would be
used to cover it and make the ground level again.
showing the cross section of the tunnels.
Normally brickwork in such a tunnel in those days
would be held together by using Roman cement. Bazalgette decided,
however, to use a new material instead: Portland cement. It
was a controversial choice, but he had concluded that it had
superior strength and durability to Roman cement when it was
submerged. He was proved right when an examination of the tunnels
over a century later showed that the Portland cement was still
holding the bricks firmly in position and did not need any repair.
Some of the considerations that made the construction
project so complex was that there were already many tunnels
and passageways under the City of London and Bazalgette's interceptor
drains had to avoid them all while continuing their steady,
downward flow. One of his biggest challenges came in 1865 when
a drain had to cross the Metropolitan Underground Railway near
Clerkenwell. This required that a one-hundred and fifty-foot-long
underground aqueduct be constructed of wrought iron, just over
the tracks. After it was complete, passengers on the trains
rode along unaware that just over their heads was flowing as
much as 60,000 gallons of sewage.
One of the most complex tasks of the project was
building the pumping stations along the route. Bazalgette took
the opportunity when he designed the pumping station at Abbey
Mills to be able to finally show his work at an above ground
location. As a result, the station is a testimonial to Victorian
By April of 1865, the first phase of the project
was completed and a celebration was held at the Crossness pumping
station to inaugurate the operation. The engines that drove
the pumps were the largest in the world at the time, each weighing
240 tons and designed to lift the sewage 21 feet up. Like the
Abbey Mills station, Crossness was a lot more attractive than
one might think a sewage pumping station would need to be, showing
an elegant Moorish architectural influence.
The Prince of Wales was the honored guest at the
Crossness opening and under Bazalgette's direction, he turned
the handle and started the massive beam engines running. During
a speech that followed the Prince spoke saying that the project
would allow everyone to look forward to the day "When London
will have become one of the healthiest cities in Europe."
Outbreak of 1866
Abbey Mills pumping station. (Courtesy
Gordon Joly licensed under the Creative Commons Attribution-Share
Alike 2.5 Generic license).
There was at least one more major cholera outbreak
before the system was completed. In July of 1866, a new epidemic
occurred in the East End of London. William Farr, a statistician
working with medical figures in England and Wales, investigated.
Originally he had been a skeptic of John Snow's idea that cholera
was transmitted by unclean water. As he gathered his data from
this most recent outbreak, however, he changed his mind. The
water delivered to sick households had all come through the
East London Water Company. The company claimed that the water
was filtered, but Farr had his doubts. His statistics indicated
that only people being supplied by East London were getting
sick. When Farr actually traveled to that part of the city and
found some residences with eels in their water pipes, he had
the proof that he needed that the company was not really filtering
its water the way they said they were.
Farr's conclusions confirmed Snow's earlier work
and soon it was accepted that the cholera was being transmitted
through the water. With a firm knowledge of how the disease
was spread, it was clear that the sewer system, coupled with
clean sources of water, would bring the reign of this terrible
illness to an end.
One of the last pieces of the new sewage system
to be put in place was the Victoria Embankment which opened
on July 25th of 1870. It was the culmination of the largest
civil construction project in the world up to the time. To build
the 450 miles (720km) of interceptor sewers, 318 million bricks
were required and 876326.915 cubic yards (670,000cm) of concrete.
Though the Queen herself cancelled coming to the
celebration at the last minute, she did knight Bazalgette for
his work four years later.
John Snow, whose work was not appreciated in his
lifetime, is now considered one of the founders of the modern
science of epidemiology. A memorial, at the location of the
deadly pump on what is now Broadwick Street, stands commemorating
Snow and his work. The plaque shows a water pump with its handle
Copyright Lee Krystek
2016. All Rights Reserved.