South East Rivers Trust (& the Wandle Trust)

Chamber Mead Community Wetland Proposal

The Hogsmill – a Chalk Stream in crisis

The Hogsmill is classified as a chalk stream, a globally rare habitat, and one of around 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 Green Lanes Stream enters the Hogsmill a few hundred metres downstream from the main river’s 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.

Example of poor water quality on the Green Lanes Stream. Oil, sewage fungus and sewage “rag” evident.

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 Hogsmill River, into which the stream flows, as evidenced through Environment Agency water quality testing. The Hogsmill is unhealthy and polluted, to the detriment of aquatic flora and fauna. This pollution also poses a public health risk to children who play in the river, as well as to dogs and their owners.

Downstream of Chamber Mead, the Hogsmill continues to flow through 2.5km 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 everyone in the local community.  

Chamber Mead – the amenity grassland area at he end of Green Lanes, Ewell. Closest postcode KT19 9SZ.

The Proposed Solution

Given the Hogsmill’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. The new channel would follow a winding path, passing through a constructed sediment trap and wetlands, before joining 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.

A plan of the proposed community wetland – the light blue line is the current flow path of the Green Lanes Stream as it meets the Hogsmill. The dark blue is the proposed diversion.
Examples of similar wetland projects. Left: Wetland within Grosvenor and Hilbert Park, Royal Tunbridge Wells. Right: Richmond Park Golf Course wetland.

What’s so great about a wetland?

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: a level of treatment of contaminants through settling of contaminated sediment in the wetlands and physical, biological and chemical processes;
  • Up to 1,000m2 of wetland habitat created: boosting diversity of habitat within the Hogsmill Local Nature Reserve;
A banded damoiselle resting on wetland plants.
  • An extra 200m of un-impacted chalk stream habitat: part of the Hogsmill River will be protected from the influence of the Green Lane Stream’s flashiness and poor water quality, benefiting flora and fauna;
  • Improvements to public health: along a section of the Hogsmill including the stepping stones, which are popular with children for paddling as well as dogs;
The Stepping Stones area is a popular paddling and playing spot for families and dogs.
  • 200m of chalk stream habitat enhanced: habitat restoration works will be carried out along a section of the Hogsmill as part of the project;
  • Increased aesthetics: reduced visible pollution;
  • Improved community amenity: the new wetlands will be an attractive addition to the Hogsmill Local Nature Reserve. Interpretation boards will enhance public appreciation of the Hogsmill and the pressures impacting it;
An example of an interpretation board erected as part of a similar wetland restoration project.
  • Educational facilities: the wetland habitat offers educational opportunities for local schools.
  • Flood risk mitigation: the project will form an important part of a catchment-scale approach to mitigate against flooding, by providing storage during heavy rain events.

Have any Question or Comment?

15 comments on “Chamber Mead Community Wetland Proposal


What will happen to the steam running through Green Lanes?


Why does the diverted water rejoin the stream after the stepping stones
This will leave the stones high and dry in the summer and spoil the enjoyment for all visitors of this feature.
Would it not be better to rejoin the stream before the stepping stones?

Jess Mead

Hello, The stream as it runs along Green Lanes will remain as it is now. The only change is that instead of running straight into the Hogsmill at the current confluence it will flow diagonally across the Chamber Mead Meadow, though some wetlands which will cleanup the water. It will then rejoin the Hogsmill just downstream of the stepping stones.

Jess Mead

Hi Judy,
The reason we’ve designed the project this way is that, at the moment, after heavy rains there are some storm overflow tanks that discharge raw sewage into the Green Lanes Stream. You can read more about them HERE. This means that after summer storms, children could be playing at the stepping stones in water contaminated with sewage. Although the wetland we propose will help cleanup some of this, because of this high flows experienced when the tanks discharge some of it will still be flowing into the Hogsmill under these conditions. So we wanted to make sure that we removed the risk of contaminated water from the stepping stones area which will have a positive benefit on public health.
It is true, as you say, that there will be reduced water volumes in this section of the Hogsmill, though we hope that this will not reduce people’s ability to enjoy the area. Low flows in chalk streams are a problem throughout the South East at the moment, as we are abstracting more water from the underground reservoirs that feed them, than the rainfall is replenishing. This problem seems to have got worse on the Hogsmill in the last couple of years. To try and improve this situation, we are working hard with other members of the Hogsmill Catchment Partnership to put pressure on the Water Companies that are profiting from the abstraction, to try and make sure they are having less of a negative impact on the environment.
If you have any more questions then please don’t hesitate to get in touch.

Grant Woolven

When is this going to happen?

Jess Mead

Hello Grant, there is no definite timeline at the moment. However it will take place in either the summer of 2020 or summer of 2021.


Why have local residence not been communicated? – how much traffic will this create during build? – what are the plans for waste ? If you are bringing water nearer to homes – how will this effect our deeds with flooding.

Northcroft Road resident

Lucy Kernot

Please can you tell me where the spread of earth on site will be ?

Mrs P Goddard

The decision to carry out this wetlands has obviously been made,however no mention of tidying up the stream running down Green Lanes has been mentioned, also with the heavy lorries running up and down the road has provision for road repairs been made as whenever any utilities are done the condition of the road deteriorates.

Jess Mead

Thank you for getting in touch. I hope that you have received a flyer though your door today and we have now published a blog with the latest project updates here:
Thorough flood modelling has been carried out during the development of this project and it has shown that there is no adverse flood risk to any property and the wetland creation actually has a slight flood risk benefit to those properties downstream. At this stage I am afraid we cannot confirm the volume of lorries leaving site as it will very much depend on whether we gain permission to spread some of the excavated earth on site. We will keep everyone updated once we have details like this confirmed. I hope that helps and please do feel free to drop us an email at if you have any more questions.

Jess Mead

Dear Lucy, thank you for getting in touch. We’ve now published a blog with all the latest project updates which contains a map of the area where some excavated earth will potentially be spread:
I’d like to stress that at this stage it has not been confirmed whether spreading of spoil on site will take place or not. It is our preferred option to do this, as it would significantly reduce disruption to local residents. However, if we do not get permission, then all spoil will be removed from site and the outlined area will remain untouched. I hope that helps and please do feel free to drop us an email at if you have any more questions.

Jess Mead

Dear Mrs Goddard, Thank you for getting in touch. This project does not involve any work along the Green Lanes Stream. It’s likely in the future that we will carry out more river cleanups along there to tidy up litter and remove rubbish from the stream, though there is no immediate plans. Regarding the roads, they are managed and repaired by Surrey Country Council and we will be having discussions with them about any future works that may take place. I hope that helps and please do feel free to drop us an email at if you have any more questions.

Anthony Partridge

Has any consideration been made to the history of this location? As i see no mention of this within this breifing. This location has a lot of history attached to it, dating back to arounf 1263, so how is any of that going to be protected or considered by this plan?

Also I dont seem to understand is this a consultation to the local community or is this a consultation that is trying to look like a done deal?

Where has the communication been with the local community?

Where is the consideration of the current land usage? In the past year the land has been vital to the local communtiy land given lock down.

Why is this diverstion even needed? The proposed habbit improvement on the existing hogsmill will still need to be done with a running stream from the other feed coming from Ewell village, that doesnt come from Greenlanes. So if this can be done with the other water supply still running? Why is the Greenlanes diversion even needed at all?

Eastcroft Resident

Jess Mead

Dear Anthony,

The wetland, and therefore diversion of the Green Lanes Stream, is needed due to the poor water quality and pollution entering the Hogsmill from the Green Lanes Stream. By passing this water through a wetland, it will remove the contaminants and clean up the water which will help improve the river for both wildlife and people.

There has been a lot of work on the history of the site which was previously pasture land and hay meadows worked by local “peasant” folk. We’ve had an archaeological desk-based assessment done by specialists and there isn’t any indication of significant activity on the site itself. From an archaeological point of view there are some areas of interest nearby and further intrusive investigation or a watching brief might be required, but this will will be decided as part of the planning application process. We’ve also had a desk-based assessment and ground investigation looking at past uses and potential pollution pathways, but all indications are there is no contamination on site.

During construction there will be some footpath diversions to keep people safe while heavy machinery is in use, but there will still be access through Chamber Mead to the rest of the Hogsmill Local Nature Reserve so people will still be able to enjoy this vital green space. After work is complete the wetland will be an asset that local communities can continue to enjoy. As part of the project we’ll be running sessions with local schools and events with volunteers to get more people out enjoying the reserve. So I hope you can see that the wetland will not prevent people having access to wonderful natural places on their door step.

We’ve been updating residents as often as we can and have recently published this blog with the latest news – A leaflet directing local residents to this information was posted to 300 local households, including those on Eastcroft Road, in January. There will be an opportunity for people to comment on the scheme as part of the planning application process.

If you have any further questions please get in touch on and we can out you in touch with the member of staff best placed to help.

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