Author: Hugh McCarthy, MIEI CIHT, chartered engineer, is vice-chair of the Engineers Ireland GB Region. The GB Region of Engineers Ireland was recently invited on a tour of Abbey Mills Pumping Station in east London and was organised by Thames Water to both promote its work as part of ‘Sewer Week’ and also to illustrate the wonder of 19^th century drainage infrastructure beneath London. [caption id="attachment_22298" align="alignright" width="300"] www.crossness.org.uk[/caption] To some, this station, along with Crossness Pumping Station in the south, are the lungs of the British capital's drainage system. They perform the dual function of collecting all storm and wastewater from north and south London before pumping it to elevated levels so it can continue its journey eastwards. From here, it is then treated at Beckton in east London before being discharged into the Thames Estuary and the North Sea. The extensive history of London’s wastewater system was illustrated to the visiting group with an informative presentation. This covered the early Roman period when London was the largest town in England up until the 19^th century when problems started to develop. What was clear is that there was very little understanding between groundwater and wastewater; particularly how one could severely affect the other. While initial waste disposal involved merely disposing all household waste onto the street, this was easily washed away by rainwater or later swept away by designated sweepers. As this was low in volume, this was generally acceptable. The first problems started to arise with the advent of piping systems used to pump both drinking and wastewater through the city. This allowed greater volumes of water to be both distributed into and out of households and business. As the capacity of the system increased, so too did the volume of wastewater being discharged. Clearly, one man and his brush was no longer an acceptable form of waste management for an emerging global metropolitan city. So, to solve this public waste issue, permission was granted to discharge all wastewater into the Thames. What could possibly go wrong?

'The Great Stink'

Between 1849 and 1854, more than 25,000 Londoners died as a result of a cholera outbreak. This represented more than 0.5 per cent of the population and there was no sign of the issue going away. It was when the ‘The Great Stink' occurred in 1858 that a solution was sought. As effluent was running down the Thames, lime was initially poured into the river to mitigate the smell. However, it wasn’t until it got so unbearable in parliament (with MPs even resigning in order to avoid Westminster) that Joseph Bazelgette, then an assistant surveyor in the London Metropolitan Commission of Sewers, started to come up with a feasible plan. While he was developing solutions before the Great Stink (1854-56), it wasn’t until local politicians were being inconvenienced that progress started to be made. Broadly speaking, Bazelgette’s plan involved a vast series of 0.9m diameter sewer pipes throughout London feeding into larger 3.0m artery pipes which then led to Abbey Mills Pumping Station in the north and Crossness in the south. As wastewater had to travel as far away as Kensington in the west, simple gravity drains would result in wastewater hitting a ‘dead-end’ deep below ground. [caption id="attachment_22300" align="alignright" width="300"] No ordinary pumping station[/caption] So, Abbey Mills and Crossness provided the key function of pumping this to a higher elevation of 15m above the original outfall level and continue towards the Beckton treatment plant in the Thames Estuary. This has broadly been the system up until the present day in London. While additional pumping stations have been added to increase network capacity, Abbey Mills and Crossness remain the most prominent stations on the drainage network. The building itself is a marvel and is more akin to a mansion than a sewage pumping station. It is Grade 2 listed with many elements internally retained from the original station. It was sandblasted prior to the 2012 Olympics as it's located relatively close to the athletics stadium. As part of cost-cutting measures, it was initially proposed to just sandblast one side of the building (i.e., the one exposed to passing journalists) but it was eventually agreed to clean the entire building. Two prominent chimney stacks used to be on-site to power the station up until the 1930s. However, these were demolished during the Second World War as it was feared that a bomb strike could lead to them collapsing onto the roof of the building. As the station had already been electrified, their usage was redundant. Walking around the exterior, there are endless, subtle designs such as fruit-based carvings into various arches, dragons doubling as roof drainage elements, and an array of unique stone carvings at various points, both internally and externally. What is also admirable is the exterior - which wasn't planned so that it would be on public display - but which is still a remarkable design.

‘Dr Crane’s not here right now’

The site visit took a turn for the surreal when we were led into… Arkham asylum. As it turns out, one building has been part-used as the set for the 2005 film ‘Batman Begins’ and other film prodictions. Our tour guide informed us that the building was used for a scene between Batman and the Scarecrow. [caption id="attachment_22302" align="alignright" width="300"] Welcome to the madhouse[/caption] The fact that we were told about Batman Villains by a portly man in a fine pinstriped suit and an elegant umbrella led to comparisons with similar villains (clue: not the Joker). The building was also used for an A-ha music video with those in the group aged between 33 and 41 nodding approvingly.

Hi-ho, hi-ho, it’s off to the Victorian drain we go

Following the tour of the station, we were formally suited up in gloves, white overalls, extra thick boots, harnesses, waterproof socks and hardhats before our descent into the ancient London sewers. Like the pumping station, the walk through the sewer was amazing, particularly as the brickwork looks like it is 20 years old when in reality it’s more than 150. Surprisingly the smell wasn’t as bad as one would have thought. This was explained by the fact that the system mixes with rainwater and also domestic water, and the wastewater is significantly diluted by the time it reaches the treatment plant. Despite this, we were still keen not to fall over. [caption id="attachment_22501" align="alignright" width="300"] GB region visiting group[/caption] As the station collects all the wastewater from all London households it also includes items that are not recommended to be flushed down a lavatory. This was quite clear as we waded through discarded mobile phones, cutlery (a lot of spoons), and clothing. A large number of needles also get flushed, hence the need for thick sole boots. The sewers have also been utilised in recent times to carry service cables along the sewer network. As digging up roads is a costly exercise, this alternative option offers something less disruptive. An example of this was 12km of cabling being laid along the roof of the sewer between Newham and Tower Hamlets. While the tour of the sewers was informative,we was still more than happy to return to the surface for some fresh air. Later that week, I left work in Southwark and chose to walk randomly home via the Embankment. It was by chance that I noted a bust of Joseph Bazelgette by the riverside. This reminded me that it was Bazelgette who created this part of London. As his drainage solution involved routing pipes through this affluent (as opposed to effluent – Ed) area of London, he was politely encouraged to find a solution that avoided digging up people’s streets and gardens. So, Bazelgette did what most engineers did at the time and just created a new area of London – the Embankment. This involved narrowing the Thames on its northern side and reclaiming about 90,000m² of marshland. [caption id="attachment_22308" align="alignright" width="300"] Joseph Baselgette[/caption] Once this was done, the proposed piping systems ran along this new embankment structure with roads built on top and the District rail lines running underneath. It was a further example of how Baselgette’s work surrounds us in London, with the workers at Abbey Mills providing a vital service on a daily basis. Something we should all appreciate. Hugh McCarthy, MIEI CIHT, chartered engineer, is currently working with Transport for London and is vice-chair of the Engineers Ireland GB Region. After graduating with a structures degree from CIT in 2008, Hugh has mainly been involved in urban road design, traffic modelling, and road safety schemes in both the UK and Ireland. He is currently leading on the Stratford Gyratory two-way project in east London. Twitter: @EngineersIrlGB