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18th April 2019
The Egg is one of the most common shapes you’ll see at Easter time, symbolising new life, birth and coinciding with the English springtime, but it also has an important place in the history of Civil Engineering in the UK.
Back in the mid-1800s, the Industrial Revolution had led to the creation of far larger cities than ever seen before, as people moved from rural homes into the industry that had emerged. This increase of population density created new problems for civil engineers that hadn’t been encountered before, particularly with regards to transportation and sanitation.
In London, this reached a head in the “Great Stink” of 1858. Without formal sanitation systems beyond the culverting of rivers, the River Thames had taken the brunt of the new sewage being produced. Additionally, the combination of raw sewage, high temperatures, and low winds had created serious problems for everyone within the city with cholera epidemics and other infectious diseases adding to the literal “stink”.
In response, Joseph William Bazalgette (championed by the better-known Isambard Kingdom Brunel and later 24th President of the ICE) was tasked with constructing central London’s first major sewer network, ordering London’s cesspits be closed and developing a network of 82 miles of main sewers and 1100 miles of street sewers along with pumping stations and balancing tanks to transmit waste away from the city.
It is here that the egg shape found its place in civil engineering history. Sewers at the time were built from bricks and the large sewers required had to be able to withstand the weight of the development above and move waste effectively regardless of flow levels. An egg shape is incredibly strong when under compression and, by turning it upside-down, closely resembled a V shaped channel, causing water velocity to increase at low flow rates helping in the removal of solids which would have been left behind in a circular sewer.
These two properties made the egg the perfect shape for London’s new sewers. Many of the original sewers are still in use today thanks to Bazalgette deliberately over-sizing his network and sewers are occasionally still constructed with this cross-section when encountering wide variations in flow.
Bazalgette’s sewers were effective in decreasing cholera, typhus, and typhoid rates in London, saving countless lives and highlighting the importance of effective drainage.
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