The medieval city

The first London sewers were merely sloping open ditches that used gravity to convey sewage and rubbish into the River Thames. By the beginning of the thirteenth century, population growth had rendered the existing water supply inadequate, and twelve new water conduits were constructed. These pipes were up to 1.6 km in length, and used gravity to transport water from natural springs into the heart of the city. Wealthy Londoners sometimes obtained permission to bring a connection into their homes, but for everyone else, water was hand-delivered from the conduits.

The earliest recorded mention of the conduits comes from a fourteenth century document, which ordered the construction of a conduit to remove wastes from the King’s kitchen.

However, during the Middle Ages, most people simply threw their waste from upper storey windows out onto the street, where the slops drained into gutters. Sewage was collected in cesspools, and privy-cleaners periodically gathered the waste to be deposited in landfills outside the city or on the banks of the Thames.

Medieval water infrastructure was similarly rudimentary. It was not uncommon for Londoners to drink water taken directly from the river, although this was often polluted with sewage.

In the early modern period the city’s population rose from an estimated 50,000 in 1530 to approximately 225,000 in 1605 due to increased trading and immigration of the Tudor golden age. In 1613, a three metre wide canal, known as the ‘New River’, began transporting water approximately 37 miles from springs in Hertfordshire to inner-city London. This source still forms a valuable part of London’s water supply today.

A smelly problem emerges

As the population grew and industry increased, wastewater was becoming an increasingly odorous presence in the growing city. To combat this problem, King Henry VIII decreed that homeowners were responsible for cleaning the portion of the sewer that travelled through their property, and established a Commission of Sewers to enforce this regulation.

However, it was not until 1668 that London’s oldest proper sewer was constructed at Ludgate Hill. It was originally an open channel, large enough to be used by boats, but was covered in 1732. More sewers were built in the early 1700s, and were typically constructed from natural watercourses.

Yet, these were primarily used for stormwater, and most homes still relied on cesspools. For those living in the houses that lined London Bridge, a simpler option was available – simply dropping their waste straight into the river.

Bazalgette’s brilliant scheme

During the first half of the nineteenth century, London more than doubled in size as the industrial revolution led to the elevation of the British Empire and its capital led the world. Yet no new wastewater infrastructure was developed. As a result, the Thames effectively became an open sewer, and thousands of Londoners perished in devastating cholera epidemics.

At the time, it was widely believed that cholera was spread by the smell of sewage, known as the ‘miasma’. Hence, health officials argued that removing the source of the stench was an urgent imperative.

However, what stirred the government into action was not the deaths in the slums, but the Great Stink of 1858, in which the Houses of Parliament, located on the banks of the Thames, were infected with the noxious stench that had enveloped the city.

After being forced to endure the Great Stink, Parliament assigned Joseph Bazalgette, Chief Engineer of the Metropolitan Board of Works, £3 million [approximately £2 billion in today’s money] to enact his innovative scheme to remove wastewater from London. Bazalgette planned to build new sewers to intercept the existing drains before they hit the Thames, then, relying on gravity, these sewers would transport wastewater down the Thames Valley. At Crossness, the sewage would be pumped back to ground level, before being dumped at sea during high tide.

Between 1859 and 1865,nearly 18,000 km of sewers were installed, using 318 million bricks. Most of the tunnels were constructed using cut and cover techniques, although mining was also used in some sections.

The tunnels were designed with an oval shape, which provided added strength and created an uninterrupted flow, and constructed using Portland cement, a new material with the durability required to withstand the weight of London.

Also, displaying great foresight, Bazalgette built the sewers with an extra 60 per cent capacity to account for future growth.

Early tunnelling

As well as being the site of one of the first modern sewer systems, London also witnessed some early advances in tunnelling, a technology which rapidly advanced in the nineteenth century in response to the demands of industrial development.

The most famous example is the Thames Tunnel, which is still used today for the East London underground. The Tunnel, designed by Marc Brunel and constructed by his son Isambard Kingdom Brunel, was the first use of the tunnelling shield. Like many tunnelling jobs, it was situated not far below the riverbed, and encountered very soft, saturated soils. The tunnel started in 1825, and was opened to the public until 1843.

Marc Brunel’s first patent for a tunnel shield was in 1818, and is the basis of modern open shields, including individual cells or compartments and the use of hydraulic jacks. He originally conceived using a large circular shield, but due to manufacturing problems Brunel developed a rectangular shield in 1823 to drive the large tunnel under the Thames.

British engineers P.W. Barlow and J.H. Greathead obtained a patent on a circular shield in 1864, which introduced major innovations still in use today, including cast iron segments to line the tunnel, compressed air to keep water at bay, and a grouting pan to inject grout into the voids behind the segments.

In 1870 this Shield was used to construct the Tower Subway, the world’s first underground tube railway. Previously the tunnels were developed by means of cut and cover. The cable operated train was used as a shuttle service between the two banks of the Thames. Due to poor patronage it was open for less than a year, however many other tunnels constructed at this time remain in operation today.

Bullion and bombs

London’s tunnel network has also been the site of several intriguing incidents in the city’s history.

In 1836, the Bank of England vault was accidentally infiltrated by a sewer-worker engaged in repairs. Although he could have easily carried away a fortune in bullion, this upright citizen instead informed the Bank Directors of the security breach. As his story was initially doubted, the man arranged to meet the Directors in the vault one evening, and dramatically emerged from under the floorboards. For his honesty, the Bank rewarded him with £800.

London tunnels also became a centre of activity during World War II. The War Rooms, constructed as a bunker originally covered three acres and came into operation in 1939. The centrepiece of the War Rooms is the Cabinet Room itself, Winston Churchill and the War Cabinet used the underground network to conduct more than 100 meetings up until the end of the war.

Underground constructions such as railway stations were used during World War II as air raid shelters. In 1942, during the London blitz, an underground refuge known as the Kingsway Tunnels was constructed to provide air-raid shelter for up to 8,000 people, and be used as government headquarters in the event of invasion. However, the tunnels were never used as a shelter for civilians, and towards the end of the war they were taken over by the research and development arm of MI6. After the war the Post Office ran the telephone exchange from the tunnels and now its successor, BT, has put them up for sale.

Twenty-first century London

Today, Londoners enjoy a first class water and wastewater system, that enjoys the benefits of innovative Trenchless Technology installation and repair techniques. Dumping sewage in the river and at sea ceased entirely in 1997, and the Thames is once again a healthy waterway, home to fish and waterbirds.

The private company Thames Water is now responsible for managing this underground infrastructure, and currently supplies 8.5 million residents with drinking water, and removes sewage for 13.6 million customers in London and the Thames Valley.

Today, Londoners enjoy a first class water and wastewater system, that enjoys the benefits of innovative Trenchless Technology installation and repair techniques. Dumping sewage in the river and at sea ceased entirely in 1997, and the Thames is once again a healthy waterway, home to fish and waterbirds.

The private company Thames Water is now responsible for managing this underground infrastructure, and currently supplies 8.5 million residents with drinking water, and removes sewage for 13.6 million customers in London and the Thames Valley.