Go to content
Two industrial water pumps sit on a structure next to a settling pond.
The Chilterns tunnel construction site has a specialist water treatment plant.

Water supply and management

How water is carefully managed during construction

We are managing and conserving water supply during construction and will leave a legacy of water resilience.

HS2 has introduced the latest tunnel-boring technology, and has spent over £100m enhancing water treatment capacity in the region to ensure the highest water quality in these areas.

Building HS2 requires careful use of water. The Chilterns tunnel boring machines are specifically designed to protect ground water and be as clean as possible. They use water to carry away excavated material as a slurry.

We are innovating in water management too. Worksop-based Wright Engineering has built a closed loop water treatment plant, to efficiently recycle and reuse the water, at the tunnel’s south portal site.

Everything we do with the water environment is regulated by the Environment Agency in according with the existing stringent regulations.

HS2 also works closely with Thames Water and Affinity Water to provide all the water needed by construction from existing resources. We won’t place any additional burden on the chalk aquifer.

Chilterns rivers and aquifer

HS2 is confident that construction will not affect the flow of Chilterns chalk rivers like the Misbourne and Chess. The choice of tunnelling technology and working methods have been optimised for the local geology to ensure that the integrity of the chalk at depth beneath the rivers is maintained. Note that these rivers have a history of dry periods and intermittent flows. You can check how the River Misbourne is flowing by viewing an Environment Agency measuring station’s information.

River Misbourne river levels

The footprint of the HS2 Chilterns tunnel is tiny compared to the aquifer unit it will pass through and on which the local rivers depend. The Mid Chilterns Chalk groundwater body covers an area of 730 square kilometres. The tunnel is 16 kilometres long and each of our tunnelling machines is only 10.2 metres wide.

A future benefit: water resilience

The need to protect the environment leads us innovate in the way we tunnel and with our water management infrastructure.

It includes a new link between two water company areas. That could mean a more resilient domestic water supply for areas of north and west London in the future.

Preparing for climate resilience

Find out about the ways HS2 is also designing in climate change resilient features across the whole railway to enable it to withstand the impact of climate change and extreme weather

Building a climate-resilient railway

Finally, HS2’s Phase One construction and operation carbon footprint, over 120 years, will emit less carbon than the road network does in one month. So, it can then provide rail journeys that emit 7 times less carbon than a car journeys.

Carbon – putting Britain on track to a net zero carbon future

HS2 and Bentonite

On HS2, Bentonite mixed with water is mainly being used in the construction of the ventilation shafts to reinforce the wall excavation before the concrete is pumped in.

Find out more