Chamber Mead Wetlands

We are building a series of wetlands to help conserve the Hogsmill River – a much-loved chalk stream in south London. This includes cleaning 500 million litres of water through natural systems to combat pollution.

This project is part of a wider partnership between the Rivers Trust and The Coca-Cola Foundation to help clean some of Britain’s most polluted rivers, reduce flood risk, and create new wetland habitats in both rural and urban locations across the country, replenishing 1.6 billion litres of water.

  • Delivery expected


Why the Hogsmill?

The Hogsmill River is a cherished chalk stream in south London. Flowing through the Hogsmill Local Nature Reserve in Ewell, the river is very popular with families and dog walkers.

Chalk streams like the Hogsmill are globally rare habitats, with only 210 worldwide. These special rivers give rise to a unique set of species that depend on the clean, chalk-purified water and are very sensitive to pollution.

Sadly, the Hogsmill has poor water quality – suffering pollution from a range of sources.

© South East Rivers Trust

A poo-luted river

The Green Lanes Stream tributary joins the Hogsmill a few hundred metres downstream from its source. This tributary brings with it a cocktail of pollution, receiving road runoff from Epsom town centre and nearby industrial areas.

During heavy rainfall the river can also be impacted by discharges of untreated sewage and stormwater from the Epsom Storm Tanks.

This pollution is not only a threat to the chalk stream but also poses a public health risk to children who play in the river and to dogs and their owners.

Polluted water from the Green Lanes Stream entering the Hogsmill chalkstream © South East Rivers Trust

Wonderful wetlands

Wetlands are a nature-based solution to improving water quality. Water that drains through wetlands is gradually filtered by plants and captured in the soil, intercepting and treating pollution.

The Chamber Mead Wetland will do exactly that. It will intercept the Green Lanes Stream, filter and clean the water through a series of wetlands before rejoining the Hogsmill with cleaner, safer water.

Wetlands provide multiple benefits. They sequester carbon, provide flood storage, mitigate the impacts of droughts by storing water in the landscape, and boost biodiversity.

Image by Meatle from Pixabay

A partnership project

Chamber Mead Wetlands is a collaborative project led by the South East Rivers Trust. Our partners include the Hogsmill Catchment Partnership, the Environment Agency, and Epsom and Ewell Borough Council.

The partners have completed a feasibility study investigating how water quality from the Green Lanes Stream can be improved at the same time as improving open space within the Local Nature Reserve for people and wildlife.

The favoured option involves diverting the Green Lanes Stream through Chamber Mead meadow. The new channel would follow a winding path, passing through a constructed sediment trap and wetlands, before entering back into the Hogsmill river approximately 200 metres further downstream.

© South East Rivers Trust

What will change?

The project will bring multiple benefits to the Hogsmill’s health and ecology, provide varied habitat and increase biodiversity, benefit public health and boost local amenity value.

  • Improved water quality
  • Reduced risk to health from contaminants and sewage based pathogens
  • An extra 200m of un-impacted chalk stream habitat
  • Up to 1,000m2 of wetland habitat created
  • Enhanced aesthetic value and reduced visible pollution
  • Outdoor educational opportunities for local schools
  • Improved community amenity with the new wetlands forming an attractive addition to the Hogsmill Local Nature Reserve.
Image by 16081684 from Pixabay

When will this happen?

We are hoping to create this wetland in 2023.

Planning permission was granted in July 2022.

The application received lots of support.

“What an excellent plan to improve the water quality while at the same time making improvements for wildlife in the area.”

We are now working to secure final permissions and funding to allow construction to go ahead.

We will keep this page up to date with the latest news. If you wish to speak to us about the project, please email us at

Image by marcelkessler from Pixabay

Thanks to our supporters

Coca-Cola Europacific Partners
The Coca-Cola Foundation
Epsom & Ewell Borough Council
The Rivers Trust
Thames Water
Environment Agency logo