Thames Tideway Tunnel: the Future of London Sewerage Systems?

By now, you have probably heard about the latest project of London, The Thames Tideway Tunnel; but the question everyone is asking is what exactly is it? Well you're in luck as that is what we will be discussing here.

The Thames Tideway Tunnel is the solution that Bazalgette Tunnel Ltd came up with to overcome the excess overflows that the current London sewerage system has. The proposed design of the tunnel is that it will be 25 km long and 65 meters deep; it will run from Acton Storm Tanks, under the tidal section of the Thames, through central London and make its way to the Abbey Mills pumping station.

The project was due to start in 2016 and is expected to be completed by 2023 with the total estimated cost ofthe project being around 4.2 billion GBP; the cost of which will be covered by Thames Water customers, regardless if they are living in or out of London, with their water and sewerage bills being estimated to increase up to 80 GBP a year by the time 2020 comes around. There have been some discussions regarding cheaper alternatives. An example would be creating more green spaces around London to soak up the rainfall which will reduce the amount of water that drains away into the sewers but also increase the overall health of the environment. However, it has been decided that the best option, in the long term, would be to proceed with the creation of the tunnel.

Originally, when the system was designed in the 19th century by Sir Joseph Bazalgette, it was estimated to only serve four million people with a fail safe being implemented for overflow to go into the Thames river through 57 combined sewer overflows (CSO) situated by the banks of the river; this failsafe was to stop sewage from backing up and flooding people's homes. Fast forward a hundred or so years later and the overall population of London has doubled making the current system inadequate as it was not designed to take that much combined sewage, with most of the areas built later in outer London having their own sewerage system and rainwater infrastructure built to deal with their sewage.

When the sewer system was first designed, it was only predicted to overflow 12 or so times every year, but with the population increase, this figure has increased to around 60 times a year. Due to this, CSOs have polluted the Thames to the point that the river is in breach of the EU Urban Waste Water Directive.

As stated, the Thames Tideway Tunnel is going to be used to deal with the overflow problem London has, and it works by intercepting 34 of the 57 CSOs. The discharge points of these 34 CSOs will be diverted and connect to the tunnel which will be located underneath the Thames. This means that instead of polluting the river further, the waste water will be stored underneath it and be pumped up to the Beckton Sewerage Treatment Works, where upon treatment, the cleaned water will be released into the river, hopefully resolving the pollution that has occurred.

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