Thames Tideway Tunnel: Project Overview and Engineering Challenges

Getting access to the right information you need for a project is essential for better results. This is when WINDCRANE can be used in various applications beyond wind monitoring and is adaptable for a variety of complex projects.

London currently has a Victorian-era sewage system, designed and built by Sir Joseph Bazalgette in the late 19th century. The project was a response to the Great Stink of 1858, which overwhelmed the existing sewers at the time. Industrial waste and untreated sewage accumulated on the banks of the River Thames, causing a foul smell in London and spreading infectious diseases. The Thames Tideway Tunnel will increase the capacity of the existing sewage system, to keep up with urban growth:

• The system was designed for a population of 4 million, more than enough capacity for the 2 million Londoners in the late 19th century.
• Bazalgette’s sewage system has received proper maintenance and still works fine, but London’s population is much larger today.
• There are now over 8 million people in the city, and the sewage system has reached peak capacity again.

The Tideway is the part of the River Thames that is affected by tides. This means the river can flow back into the sewage system during a high tide, and this represents an engineering challenge for the tunnel project. This is why a WINDCRANE Max unit is being used to monitor the river level with respect to the tunnel level.

WINDCRANE is normally used to track wind speed and direction. However, the unit offers compatibility with almost any sensor - analog or digital - and it can handle up to 14 simultaneous inputs. This makes WINDCRANE suitable for various applications beyond wind monitoring.

Project Background

The current sewers are designed to spill over at the River Thames when they reach maximum capacity. This was a rare occurrence decades ago, but there are now over 50 spillovers per year. Over 18 million tonnes of untreated sewage reach the Thames annually, and this has a severe social and environmental impact. Without any measures to reduce it, the annual sewage discharge could increase to 70 million tonnes by 2030.

Currently, it only takes 2mm of rainfall to cause sewage overflow into the river. The Thames Tideway Tunnel is an ambitious project to solve this issue, redirecting excess sewage to a tunnel under the river, and reducing water pollution.
 

The following are some of the main features of the project:

• The Thames Tideway Tunnel has a diameter of 7.2 meters and a length of 25 kilometres, built separately as three converging sections.
• The tunnel depth ranges from 30 to 65 metres below the River Thames.
• The tunnel is designed for a service life of 120 years, and is planned to start operating in late 2022.
• The estimated project cost is £4.2 billion.

Measuring the water level is important in any construction project that interacts with natural bodies of water. During the construction process, increases in water level represent a threat, since they can flood work in progress.

In the case of the Thames Tideway Tunnel, monitoring the river level is a continuous requirement, since the tunnel will interact with the river for decades and this is why WINDCRANE brings added value in monitoring this application. Since it comes with a cloud storage system that records historic data. If the device is lost during an extreme weather event, its information is safely stored in the cloud.

The platform can also send automatic notifications to key project staff members when dangerous conditions are detected, such as high tides in the case of the Thames Tideway Tunnel.

Main Technical Challenges for the Thames Tideway Project

In addition to the scale of the project, the Thames Tideway Tunnel brings several engineering challenges. These include potential backflow from the Thames River, smell prevention, and a 53-metre drop between the existing sewers and the tunnel.

The 25-km tunnel is under the Thames Tideway - the 160-kilometre river portion that is affected by tides. Weather monitoring is an important element of the project, for the following reasons:

• Since the existing sewers also carry rainwater, they normally reach maximum capacity during heavy rain. In other words, the amount of water discharged strongly depends on the weather.
• Monitoring the tides is also important, since the Thames Tideway level rises and falls by up to 7 metres each day.
• WINDCRANE Max is being used to track the tides, by measuring the difference between the tunnel datum and the Thames River level.

To prevent backflow from the River Thames, the project will include special valves that close in response. This ensures that only sewage reaches the new tunnel, and not backflow from the river. To prevent odor issues, the tunnel will use a ventilation system with activated carbon air treatment.

There is a 53-metre drop between the Victorian sewers and the new tunnel, and the energy dissipated by water in free fall can eventually destroy the base. To dissipate energy and minimise air entrainment, the Thames Tideway Tunnel will use vortex drops for the 53-m fall. These drops induce laminar flow, preventing turbulence and protecting the tunnel base.

WINDCRANE Max is not limited to wind monitoring, and it can be used in any application where a critical variable must be monitored. The Thames Tideway Tunnel is an example: preventing backflow from the river during high tides is very important, so that the tunnel capacity is not overwhelmed.