NEC3 Contract Projects: The Thames Tideway Tunnel

One of the biggest construction projects in progress currently in London is the Thames Tideway Tunnel. In fact, it is one of the largest construction projects of its type in Europe – a real feat of ingenuity and engineering in UK construction managed under the NEC3 contract.

Due to the vast increase in population in London, the current sewage system is not suitable to handle the significant expansion of the capital city. The sewer system in London is a combined system which combines storm run off water and wastewater all run through the same route. Normally this is fine, but during heavy rain the sewer fills up rapidly, overflowing and spilling out into The Thames river. Not ideal!

Unfit for Purpose

There are a total of 57 combined sewer overflow sites on the Thames which were originally designed to overflow roughly 12 times per year in the 19th Century. Now these ‘CSO’s’ overflow around 60 times per year, polluting the river Thames and resulting of the system being in breach of the EU Urban Waste Water Directive.

The sewers in central London do not serve the entirety of the population within the M25. Many new independent sewers have been built to help manage the population increase. One of the biggest factors in the increase of water flowing through the main sewer is due to the increase of storm water which is a result of the immense increase of paving over of London.

Current & Future Project Plans

The Thames Tideway Tunnel project was started in 2016 and will take approximately seven to eight years until completion. The tunnel will run for over sixteen miles and have a diameter of twenty-four foot. It will run from Acton at below 98ft through to Abbey Mills at 230ft. The sheer scale of the size and depth makes this one of the most ambitious projects in Europe.

The tunnel will intercept the water heading for 34 of the CSOs before it overflows into the river. Instead of flowing straight into the river, it will be stored in ‘The Super Sewer’ to the be pumped into Beckton Sewerage Treatment Works. Here it will be turned into clean water and then released into the river when it is safe for the environment.

The total cost of the the Thames Tideway Tunnel project is estimated to be around £4.2Bn. Thames water customers will be footing the bill for the sewer improvements with an expected rise in their yearly bills of up to £80 per year by 2020. The government has provided a financial guarantee in the event of significant unseen costs, but the tunnel will be owned privately by the new company Bazalgette Tunnel Ltd, trading as Thames Tideway Tunnel Ltd.

This is the first article of a series in which we will be looking into the most prominent NEC contract managed projects around the world. If you would like to know how we can help with your NEC3 managed project, please don’t hesitate to get in touch.