South East Rivers Trust (& the Wandle Trust)

Wetland creation to help the Hogsmill


Latest news on the Chamber Mead wetland creation project.

Updated 20/01/2021 – The blog below has been updated to reflect the fact that the decision has now been made not to spread excavated earth on the area of scrubland previously identified as having potential to spread material. The majority of material created when digging the wetland areas will be removed from site in lorries.

The Chamber Mead project will breathe life back into the Hogsmill by creating a new wetland habitat that will help clean contaminated water before it enters the river. The Green Lanes Stream joins the Hogsmill just a few hundred metres from its spring source, but brings with it high levels of polluting substances. By creating a series of wetlands through Chamber Mead, this project will allow natural cleaning processes to reduce the impact of sewage and urban pollution on the Hogsmill. 

Why do we need a wetland?

The Hogsmill is one of only 200 chalk streams in the entire world. These special rivers are renowned for their crystal clear waters and extremely high quality water. This means that when in a healthy condition, these rivers support a wonderful array of wildlife, which can only thrive in these rare, pollution-free streams.

Unfortunately, the Hogsmill cannot reach its spectacular potential as it suffers from the chronic pollution issues that affect many urban rivers. Oil, dirt and a cocktail of toxic substances are washed off surrounding roads straight into the river each time it rains. Sewage makes its way into the Hogsmill from a worrying array of sources, which pose a danger to people’s health as well as negatively affecting the river’s wildlife. The Green Lanes Stream, a tributary of the Hogsmill, is a particular hotspot for these kinds of pollution.

The Green Lanes Stream is a hot spot for pollutants including oil and sewage.

Many options for reducing the input of pollutants from the Green Lanes Stream into the Hogsmill have been explored by the Hogsmill Catchment Partnership. Creating a series of wetlands at Chamber Mead is the preferred solution, as this will work with natural processes to achieve this aim, as well as producing many other benefits for people and wildlife.

How do we know a wetland will work?

Constructed wetlands make use of the natural purification processes of vegetation, soils and microbes to remove polluting substances.

As dirt is washed off roads, it will settle at the bottom of the wetland after reaching an area of slow water flow, reducing the input to the Hogsmill. Excess nutrients from sewage inputs will be absorbed and stored by wetland plants, and chemicals including oil will be broken down by micro-organisms.

These are well studied natural processes, and the wonders of wetlands are being used all over the world in similar projects. Many sewage treatment works are also constructing wetlands to treat the water they discharge further before it reaches the river.

How will Chamber Mead change?

The Green Lanes Stream will be diverted to flow diagonally across Chamber Mead, re-joining the Hogsmill just downstream of the Stepping Stones. Along its new path will be a series of wetland basins, planted with native wetland vegetation to remove pollutants from the water.

By doing this, not only will the water quality be improved, but the wetland will boost biodiversity within the Hogsmill Local Nature Reserve. The new habitat created will be the ideal place for amphibians like frogs and newts, colourful dragonflies and other aquatic plants and animals.

Creating this wonderful wetland habitat will involve significant groundworks which will leave large areas of bare earth immediately after digging is complete. However, these will green up very quickly as areas of grass will be re-seeded and over 10,000 wetland plants will be added. The area may be fenced off initially to give this new vegetation time to root.

A similar wetland scheme in Tonbridge.

The wetland will provide a valuable educational resource for local schools with free lessons run by the South East Rivers Trust in the months after completion. New dipping platforms, a bridge and family activity trail will maintain and enhance access to the space, making it a valued part of the Hogsmill Local Nature Reserve for years to come.

The popular paddling spot round the Stepping Stones will be maintained and thanks to the new wetland, the water quality here will be much better, reducing the risk to public health.

When is this happening?

Delivery of the work is planned to take place over an 8 week period in the summer of 2021. An application for planning permission is expected in early 2021.

Will there be disruption during work?

Yes – we are afraid there will be some disruption to local residents and park users during construction of the wetland. We are extremely sorry for any inconvenience this will cause, but we’re doing everything we can to minimise the disruption.

The use of heavy machinery to excavate the wetlands will make it necessary to close some paths temporarily for the safety of those visiting Chamber Mead. This will be done for the minimum possible duration and a suitable alternative diversion will be put in place.

Once excavated, a large quantity of earth will need to be removed from site in a significant number of lorries. It is highly probable that access to and from Chamber Mead will be along Green Lanes which is likely to cause disturbance to local residents. Work of this nature will never occur at weekends or at anti-social hours but is likely to have to take place over several weeks.

We hope the wetland we create, and the benefits it will bring to the Hogsmill, its wildlife and local residents, will make up for this short-term disturbance.

Will there be opportunities to get involved with the work?

There will be plenty of opportunities to get involved in different stages of the project including planting wetland vegetation, removing plastic pollution and further habitat enhancement as the wetland matures.

The South East Rivers Trust will be working with local schools to run outdoor learning sessions at the wetland. If you’re a teacher at a nearby school and you’d like your class to be involved – please contact the project team on chambermead@southeastriverstrust.org

What has happened to date?

This project has been planned and developed over several years in conjunction with Epsom and Ewell Borough Council. The need for wetland creation to clean up contaminated water from the Green Lanes Stream is highlighted in the Council’s 100 year plan for the Hogsmill Local Nature Reserve, and the project is supported by members of the Hogsmill Catchment Partnership.

Part of the development process has been carrying out extensive flood modelling to ensure that creating the wetland does not increase flood risk upstream. Ground investigations have confirmed the site is suitable for conversion to wetland and a design has been drawn up with advice from wetland experts. The South East Rivers Trust has now successfully gained funding to progress this project and complete delivery of this ambitious project.

How can I find out more?

If you have any questions at all about the Chamber Mead Wetland project, or would like to discuss any concerns you have with a member of the project team, please email us on info@southeastriverstrust.org

Supported by:

Have any Question or Comment?

33 comments on “Wetland creation to help the Hogsmill

leonard grover

Get the council to sort the parking out in Greenlanes before you start running lorrys down to Chamber mead. All that is needed is restricted parking times to stop cars parking to use as a free stop for West Ewell railway station, instead of using the charged car park at the station.

leonard grover

Await reply.

Jess Mead

Dear Leonard, thank you for getting in touch and I understand your frustration with parking. However, changes to parking restrictions are completely out of our control I am afraid. You can always visit the Surrey County Council website and request a change to parking restrictions here: https://www.surreycc.gov.uk/roads-and-transport/parking/reviews
I hope that helps and please do feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

William Brown

After reading about the proposedChamberMead project I feel part of the pollution of the Green Lanes stream could be the flood outlet on the Longmead Road just near the church. This outlet has always shown signs of pollution and has in the past been investigated but never been rectified. If this source of the pollution could be rectified it could help in ensure cleaner water running into the Hogsmill River

Jackie Dodd

I would love to help with planting up when needed and have friends who might help too.

Mike Davis

I note the request for local schools to get involved.
Is there an opportunity for those of us retired and with the appropriate skills to assist in the project?

Jess Mead

Hi Jackie, there will be lots of opportunities to get involved with the project over the coming year (Covid restrictions permitting). The best thing to do is sign up to our mailing list at https://www.southeastriverstrust.org/mailing-list/ as this is where we send out information about all of our upcoming volunteer opportunities. Hope to see you along to one of our volunteer days in the near future.

Jess Mead

Hi Mike, there will be lots of opportunities to get involved with the project over the coming year (Covid restrictions permitting). The best thing to do is sign up to our mailing list at https://www.southeastriverstrust.org/mailing-list/ as this is where we send out information about all of our upcoming volunteer opportunities. Hope to see you along to one of our volunteer days in the near future.

Chris Hunt

Being one of the residents who backs onto Chamber Meads please can you confirm where the spread of earth will be on site? This is causing concern from residents.
Also, how will this affect the privacy of the gardens backing onto Chamber Mead?
I await yr reply ..

Jess Mead

Dear William, thank you for getting in touch. There are many outfalls along the Green Lanes Stream and I am afraid I am unsure about exactly which one you are referring to. Please can you email info@southeastriverstrust.org with more of a description of the location, a photo of the outfall or a map with it marked on and we can then hopefully give you an update on what has been done to date. Or if it’s an outfall we’ve not brought to Thames Water’s attention so far, we can make sure we do that. Thanks.

Lucy Kernot

Thank you for your reply to my previous message. .

Your flyer shows that the existing earth will be spread thorough out the area adjacent to homes and gardens. This area is currently cohabited by a mixture of birds and other wildlife.

Can you explain what plans are currently in place to address this.

Shaun Ferguson

Hi there. That area is heavily used by dog walkers. Once the wetland is created and wildlife moves in. How is disturbance from rampaging dogs in the wetland itself going to be mitigated? For instance disturbance of nesting birds like Reed and Sedge Warblers. Will the wetland be fenced in, partly fenced in or not at all? Let me just state I’m not against walking your dog in this area but can see the above becoming an issue in no time at all.
Great project, I look forward to see the results. Thanks.

Kip Trevor

Thank you for this, l look forward to hearing of the progress!

Jess Mead

Hi Shaun, Thank you for getting in touch. The wetland and new channel will be fenced off for the first year or two to allow the newly planted vegetation to establish. In the longer term the plan is less certain as it will depend on many different factors, though our hope is that the fringe vegetation will grow dense enough to discourage high levels of disturbance by dogs and we’ll be able to remove the fencing. I hope that helps and please do feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Angela Collins

Will many trees be cut down to make space for the excess soil and the changes you have mentioned?

What will happen to the new bridge that was put in just a few years ago joining the two park areas And cycling paths together?

This is such a brilliant plan! Whoever is the brains behind it needs to be applauded. Well done! I do see however the first comment is a complaint about parking in Green Lanes. Honestly? Some people are so negative and need to find anything to moan about. I am sure there are parking issues and lets hope they are resolved for you but moaning on a news article about a wetlands area designed to purify water isn’t the place.

Jess Mead

Hi Lucy, This was an option being explored, however this week the decision has been made not to spread excavated earth on the area of scrubland previously identified as having potential to spread material. The majority of material created when digging the wetland areas will be removed from site in lorries. I hope this alleviates your concerns regarding the spreading of earth within the area of scrubland behind Northcott Road. Please feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Jess Mead

Hello Chris, This was an option being explored, however this week the decision has been made not to spread excavated earth on the area of scrubland previously identified as having potential to spread material. The majority of material created when digging the wetland areas will be removed from site in lorries. I hope this alleviates your concerns regarding the spreading of earth within the area of scrubland behind Northcott Road. Please feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Jess Mead

Hello Angela, Thank you for getting in touch. Spreading of material in the scrubland area was being explored as a potential option. However, the decision has been made this week not to spread excavated earth on the area of scrubland behind Northcott Road. The majority of material created when digging the wetland areas will be removed from site in lorries. This means that area of scrubland will not have any vegetation removed.
Elsewhere on the project site two trees will need to be removed – one Ash (where the new channel will re-join the Hogsmill) that would likely need to be removed due to Ash dieback in the near future anyway, and a small tree where the new channel will leave the Green Lanes Stream. Both have been assessed for ecological potential and bat roosts etc. and are found to be of low value.
The new bridge will remain exactly as it is, the new channel taking flow into the wetlands will leave the Green Lanes Stream downstream of where this bridge is. A new footbridge will be installed at the other end of Chamber Mead, allowing people to cross the new wetland channel close to the stepping stones. I hope that helps and please do feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Angela Collins

Thank you for your last reply I have some more questions

How will the water at the stepping stones be improved if the new channel joins after the stones downstream?

What will happen to the stream that does not follow the new route? Will it be blocked off?

Jess Mead

Hello Angela, All water from the Green Lanes Stream will be diverted via the new wetland and the current channel blocked off to facilitate this diversion. The main Hogsmill channel that flows from the ponds at Bourne Hall and past the stepping stones will continue to flow as usual. It has a much better water quality than the water coming from the Green Lanes Stream, so there is no need for it to go through the wetland. This means that all the polluted Green Lanes Stream water that is currently flowing past the stepping stones will be diverted, leaving just the cleaner Hogsmill water for children to enjoy more safely. I hope that helps.

This is so exciting! I’d love to volunteer to help out in any way, plus I’m sure my Scout Group would be willing to lend hands.

Jess Mead

Hi Viki, there will be lots of opportunities for you and the Scouts to get involved as volunteers. If you sign up to our mailing list, that’s where we send out information about upcoming events: https://www.southeastriverstrust.org/mailing-list
Look forward to seeing you at one of our events! Thanks.

Victoria Carlisle

This is a wonderful idea . Please make the wetland area a dog free zone so that people who don’t own dogs can enjoy the area. This would also protect the wildlife as some dog owners think it is their dogs right to rampage in lakes and ponds scaring wildlife. Dog owners have plenty of spaces to walk their dogs but us non dog owners would also like a quiet space to appreciate nature. It is also crucial to keep toxic dog mess harmful to wildlife and water courses away from this area. This area would greatly benefit school children and less able people to access the boardwalks.

Johnathan Stokes

As a family, we are very excited by this prospect. However, to make it enjoyable for everyone and safe for wildlife, please can you make sure this will be a dog free zone. We need somewhere to go where we don’t have dogs using the ponds for recreation. Dog owners seem to prioritise their dogs happiness over the well being of wildlife and preservation of breeding habitats. Dogs also pollute water. Will this area be secure from dogs please? Are board walks going to be installed for disabled users? Thank you.

Jess Mead

Hello Victoria, Thank you for getting in touch. The wetland and new channel will be fenced off for the first year or two to prevent dog access and allow the newly planted vegetation to establish. In the longer term the plan is less certain as it will depend on many different factors, though our hope is that the fringe vegetation will grow dense enough to discourage high levels of disturbance by dogs and we’ll be able to remove the fencing. Outside of the immediate disturbance to the wetland, decisions about managing dog disturbance will be made by the landowners; Epsom and Ewell Borough Council. I hope that helps and please do feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Jess Mead

Hi Johnathan, Thank you for getting in touch. The wetland and new channel will be fenced off for the first year or two to prevent dog access and allow the newly planted vegetation to establish. In the longer term the plan is less certain as it will depend on many different factors, though our hope is that the fringe vegetation will grow dense enough to discourage high levels of disturbance by dogs and we’ll be able to remove the fencing. Outside of the immediate disturbance to the wetland, decisions about managing dog disturbance will be made by the landowners; Epsom and Ewell Borough Council. I hope that helps and please do feel free to drop us an email at info@southeastriverstrust.org if you have any more questions.

Jeremy Smith

This scheme looks fantastic and I can’t wait for it to be built. We live not far away (Stoneleigh) and often visit this stream on bikes or on foot. Brilliant development – bring it on.

Dan Jacobs

Marvellous idea! This is a great initiative and I fully support it. Are opportunities for more mini wetlands upstream in the Green Lanes stream itself?

Barry Smith

Hi, this is a lovely and positive improvement to the area. What a good thing. But it leaves me wondering; would it possible to improve the actual Green Lanes area of the stream? Maybe that could be a wetland too? Or perhaps some other sort of improvement could be made. It’s quite mucky and ugly at the moment.

Jess Mead

Hi Barry, Work on the Green Lanes Stream itself won’t be carried out as part of this project but is something that the Catchment Partnership would consider in the future.

Kathy Williams

We live by the Hogsmill,with two dogs to walk every day. Not intermittently. Whilst we truly support the development of the wetland, my husband is a volunteer, the Hogsmill Stepping Stones area has been our dog walking patch for more than 40 years. We are responsible dog owners who remove our waste and like in any area of nesting birds or birthing deer we are happy to put our dogs on a lead around that site. There is room for everyone. This is an area which is greatly used by local people whose dogs do not generally rampage. Locally we seem to be of the mind that we are looking forward to the improvement the wetland will bring and the diversity that will follow.

Shaun Ferguson

Can I ask will the future wetland be planted up with reeds to help with the filtration of the pollutants?
I had a member of staff from the London Wetland Center (WWT) walk around with me today and he mentioned we must make sure we use the Phragmites Reed. Reason I ask is because Reed and Sedge Warblers will only nest in this type of reed. Can we look into this please?

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