London’s new 15 mile ‘super sewer’, the Thames Tideway Tunnel, has received official government backing and is going ahead despite misgivings as to whether it’s the best solution to London’s increased sewage needs and the huge costs involved. The project is scheduled to start in 2016 and finish in 2023.

Why is the Thames Tideway Tunnel being built?

London’s original Victorian sewers were intended for a population of around 2 million, but this has risen by over four times since they were first built. The problem is one of overflow – at certain times surface water drains straight into the River Thames during periods of high demand. It used to happen a handful of times a year, now it’s a weekly occurrence.

The result is that sewage is being drained straight into the river where it stays for some three months before finally moving out to sea. Thames Water – who are behind the project – say that around 39 tonnes of raw sewage is being pumped into the river each year and the new sewer would reduce this by some 97%.


The new ‘super sewer’ is meeting heavy opposition from those concerned about the huge cost, the disruption such a major construction project will cause, and whether it’s even the best solution to the sewage problem.

Some environmental groups such as Clean Thames Now say the main reason London has a surface water issue is because there are so many hard and impervious surfaces compared to the more absorbent and open spaces of yesteryear. They claim cheaper and less disruptive solutions such as green roofs and porous asphalt road surfaces should be investigated.

The cost

The huge cost of the sewer – the width of three London double decker buses and stretching from Acton in west London to Stratford in the east – is being met by a combination of funding including consortiums of shareholders and public funds.

Of concern to some are the escalating costs – estimates originally put the cost at around £1.7 billion before swelling to the current price tag of £4.2 billion.

How will the ‘super sewer’ be funded?

Increased water bills

London residents, and some living in surrounding areas within the Thames Water catchment who won’t even benefit from the ‘super sewer’, are predicted to be facing increased water bills of some £70-80 per year to help fund the project.

According to this source, however, this may not happen as Ofwat – the water industry regulator – has refused Thames Water’s request to allow it to increase water bills between 2015 and 2020. In fact, Ofwat intend to do the opposite by instructing water companies to reduce bills over the next five years.

Investment vehicle

bids have been invited for individuals and consortiums to bid for the control of a new investment vehicle to build the huge tunnel. Wealthy investors from diverse locations such as Hong Kong and Abu Dhabi have registered interest, and it’s expected that most of the funding will be met in this way.

Government funding

the government are fully behind the project, and are prepared to back the above investment vehicle with a guarantee. They have also pledged to provide financial support for cost overruns during the construction process.

The irony

Ironically, the original London sewers encountered misgivings – not least in the areas of expense as they cost £4.2 million which equates to some £430 million today. As with the Thames Tideway Tunnel, the original sewers were designed to stop raw sewage being discharged into the river.

Fraser Ruthven is the Marketing Associate for London Drainage Facilities, one of London’s leading drainage companies. London Drainage provides a wide range of drainage diagnostic and repair services in and around London.