Is the Thames Tideway Tunnel is a Victorian solution to a 21st century problem?
Yes, the Thames Tideway Tunnel will cost £4.2 billion (i); it is intended to reduce the number of raw sewage and rainwater discharges into the River Thames and involves construction of 25km of tunnel/ sewer under the River Thames from Acton to Abbey Mills in the east and is designed to capture discharges and deliver them to Beckton Sewage Works for treatment, before discharge into the lower Thames.
The discharges arise because of high rainfall, given that London has a combined sewage system (surface water run-off and sewage are fed into a common system) unlike some other cities. Given the expense of building a totally separate system for sewage, there is an alternative solution, which is to reduce the impact of high rainfall on surface water run-off through SUDS (ii). This involves green roofs, permeable surfaces in areas of gravel geology, green infrastructure and water storage (linked to recycling of water for non potable uses) and green infrastructure. These measures can involve landscape architects. They can be paid for by charging building owners for the amount of run-off they impose on the sewerage system: so it costs less if you install a green roof which slows and reduces run-off (as happens in Dresden for instance).
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