South East Rivers Trust (& the Wandle Trust)

Chamber Mead Wetlands


The planning application for the Chamber Mead Wetlands project was submitted to Epsom and Ewell Borough Council and is now open for public comment:
Application number to search is: 21/00928/FUL
Address is: Chamber Mead Open Space Green Lanes West Ewell Surrey

Late Summer 2021 was previously the target date for construction of the wetlands. However due to delays, unfortunately this target has had to be pushed back to Spring/Summer 2022, when the ground is dry enough. This new deadline gives plenty of time for planning permission to be in place and for everything else to be ready to go in 2022.

Once completed, there will be a number of exciting volunteer and education opportunities for the local community, centred around the new wetlands.

The Hogsmill River is one of only 200 chalk streams in the world, though sadly, it has been long-suffering from regular pollution inputs of raw sewage from the Epsom and Ewell Storm Tanks, mis-connected sewers and urban runoff. Pollution harms wildlife within the river, poses a public health risk and impacts the amenity value of the Hogsmill River.

A collaborative project is being developed between the Hogsmill Catchment Partnership, the Environment Agency and Epsom and Ewell Borough Council, led by the South East Rivers Trust, to help tackle these issues. A series of wetlands within the Hogsmill Local Nature Reserve are proposed to help improve water quality, bring significant habitat, species and biodiversity benefits, contribute to flood risk mitigation and boost the amenity value of the area.

It is part of a wider partnership between the Rivers Trust and The Coca-Cola Foundation to enhance freshwater environments across England, with this project alone replenishing over 500 million litres of water flowing into the Hogsmill River per year.


The Hogsmill is classified as a chalk stream, a globally rare habitat with only 200 worldwide. Chalk streams give rise to a unique set of species that depend on the clean, chalk-purified water and are consequently very sensitive to any decline in water quality.  The Hogsmill is an important asset for the community, with the Stepping Stones within the Hogsmill Local Nature Reserve in particular used heavily by children, families and dog walkers.

The Hogsmill Chalk Stream

The Green Lanes Stream enters the Hogsmill a few hundred metres downstream from the source, adjacent to a two-acre meadow known as Chamber Mead. The Green Lanes Stream has very flashy characteristics as a consequence of draining Epsom town centre, the surrounding roads and the Longmead Industrial Estate. During heavy rainfall the river can also be impacted by discharges of untreated sewage and storm water from the Epsom Storm Tanks, and polluted runoff from roads and other hard surfaces common in urban areas.

Chamber Mead – within the Hogsmill Local Nature Reserve

As a result of this, the water quality in the river is poor, with long running and recurring pollution incidents. This has been identified as a problem for both the Green Lanes Stream and the receiving Hogsmill river, as evidenced through Environment Agency water quality testing. The Hogsmill is unhealthy and polluted, to the detriment of aquatic wildlife. This pollution also poses a public health risk to children who play in the river and to dogs and their owners.

Downstream of Chamber Mead, the Hogsmill continues to flow through 2.5 km of heavily used public green space, where children frequently paddle and dogs swim, unaware of the water quality issues. Improvements in water quality will improve this current public health issue, making it a safer place for all.  

The Solution

Given the river’s global importance, the South East Rivers Trust has been working hard to protect and restore the river for both communities and wildlife. For example, the Trust hosts the Hogsmill Catchment Partnership which brings together local stakeholders (businesses, NGOs, local government and members of the community) to understand how the river has been changed and impacted; to identify solutions; and to develop projects aimed at improving the health of the river. The Hogsmill Catchment Partnership vision “is for the Hogsmill to be a clean river, rich in biodiversity, that is a resource for an engaged local community.”

A collaborative project between the Hogsmill Catchment Partnership, the Environment Agency and Epsom and Ewell Borough Council is currently underway, led by the South East Rivers Trust. The partners are undertaking 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 (see map HERE). 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 of where the Green Lanes Stream currently flows into the Hogsmill. Interpretation boards will be installed to spread awareness and understanding of the Hogsmill, the pressures it faces and the work being carried out to tackle this.

Imagery @2019 Bluesky, DigitalGlobe, Getmapping plc, Infoterra Ltd & Bluesky. The GeoInformation Group


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, with a level of treatment of contaminants through settling of contaminated sediment in the wetlands and physical, biological and chemical processes;
  • Reduced risk to health from contaminants and sewage based pathogens along a section of the Hogsmill including the Stepping Stones, which are very popular with children for paddling as well as dogs. Notices are currently present warning the public of health risks due to poor water quality;
  • An extra 200m of un-impacted chalk stream habitat. Part of the Hogsmill, a globally-important chalk stream, will be protected from the influence of the Green Lane Stream’s flashy flows and poor water quality, benefitting chalk stream wildlife;
  • Up to 1,000m2 of wetland habitat created, boosting diversity of habitat within the Hogsmill Local Nature Reserve;
  • 200m of chalk stream habitat enhanced through habitat restoration works proposed along a section of the Hogsmill as part of the project;
  • Enhanced aesthetic value and reduced visible pollution;
  • Outdoor educational opportunities for local schools will be provided by the wetland habitat and newly restored river. Interpretation boards will also highlight how wetlands can be used to improve water quality in rivers impacted by pollution;
  • Improved community amenity, with the new wetlands forming an attractive addition to the Hogsmill Local Nature Reserve. Interpretation boards will enhance public appreciation of the Hogsmill and the pressures impacting it;
  • Flood risk mitigation as an important part of a catchment-scale approach to mitigate against flooding, by providing water storage during heavy rain events.

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