Late last month, a group of us met senior managers from Thames Water at their Hogsmill Sewage Treatment Works in Kingston.

The meeting was to discuss the state of the Hogsmill and Green Lanes Stream and the terrible pollution that Thames Water is putting into the rivers.
 
We were given a tour of the sewage treatment works by Thames Water managers who also presented to us the challenges they face in keeping sewage out of the streams.

I have attempted to the best of my abilities to write up the issues below. Apologies that it is a little long and I have been a tad slow in getting this out.
 
So, first a bit of sewage system theory as explained by Thames Water. The sewage and rainwater drainage systems in an area should be separate as the sewage needs to go to the sewage works while the rainwater should go into the water table via a soakaway or into local streams via pipes. Rainwater would naturally end up in the water table or local streams if it wasn’t for human urbanisation (our concreting and building on the natural world) and if rainwater is not deposited back into the water table or local streams then they dry up adversely impacting wildlife. Also lots of rainwater and surface water in the sewers fills them up and mean they overflow.
 
In Epsom, Ewell, Kingston and Surbiton the systems are often mixed. In some areas there is a clean separation however in large areas of the boroughs they are not.
 
The mixing can go either way with differing consequences:
 
1)    Rainwater / surface water going into the foul sewers. This is the most common problem and occurs across large areas of the boroughs eg. in large parts of the South of Epsom (the racecourse side of the town) the rainwater / surface water drainage goes into the sewage system. This causes major problems when it rains meaning the sewage system regularly overflows at the storm tanks in Epsom and Ewell depositing large amounts of raw sewage into the streams. The problems could be fixed by:
-       fitting larger storm tanks,
-       separating the systems fully or
-       by installing intelligent sewers that can hold back flows in the system at times of heavy rainfall effectively using the whole system as a massive storm tank (currently Thames Water's preferred solution).
 
2)    The foul sewers from homes and businesses going into the rainwater / surface water drainage system, this is commonly known as misconnections. Most homes’ and businesses’ foul sewers are connected correctly however in the Hogsmill catchment there are around 200,000 properties and 400,000 people and some aren’t (the number is estimated to be in the hundreds) and that means that hundreds of homes’ and businesses’ sewage is going into the rainwater system everyday and then into the rivers. Where these mistakes have been made it is up to the property owner to correct them. If property owners can’t afford to do this, then sometimes Thames Water can help.
 
Thames Water said at the meeting that they accepted that any amount of sewage going into the streams was unacceptable (good start) and that their plan was to reduce the amount of sewage discharges across their area by 50% by 2030 and by 80% in sensitive catchments such as the Hogsmill by 2030.
 
The Hogsmill is deemed to be a sensitive catchment as it is a chalk stream that should be a haven of wildlife and is rare in the natural world.

I asked the Thames Water managers, being a senior manager too in a different industry, if they had a plan to achieve the 80% reduction at the meeting and they didn’t seem to have one which I found both surprising and worrying. I asked them what project management checkpoints they had on the way to the 80% reduction – again I got no clear reply which would seem to suggest that they have no plan.
 
When asked by me to discuss constructive proposals to fix the pollution, they did not seem positive about enlarging the storm tanks which I put forward as one solution. At first the senior manager said the one at Ewell would need to be enlarged 10x to make any real difference but when pressed by me why, say doubling their size wouldn’t make any difference, he didn’t seem to have any clear answers.
 
The senior manager did talk about creating intelligent sewers which would effectively enlarge the storm tanks by using the sewers as one large storm tank. A series of sensors and gates would be able to close off parts of the sewers damming them at times of heavy rainfall and holding water back. This seems like a good idea but there is no detailed plan to actually do it.
 
Thames Water are currently creating a 25 year plan for the area and its draft is available here - https://www.thameswater.co.uk/about-us/regulation/drainage-and-wastewater-management

There has been a consultation period on the plan however it has now closed and it had closed by the time we met them on 30 September.  The final plan is due to be published in March 2023.
 
Having read the draft plan for the area, objectively, it does not appear to provide a feasible way forward to meet the objectives of reducing pollution into the streams by 80%. I worry that it’s more a sophisticated PR exercise than an actual plan to spend money, deliver projects, and fix issues. I hope that Thames Water can improve it and I would be interested to hear what you think of it too if you are able to read it (link above).
 
I hope that this update has been useful. Well done if you’ve reached this far! I will be back with another soon with some proposed next steps for the campaign though...
 
…As a starter for ten, and at a high level, I believe that we need now is a credible plan from Thames Water of significant investment in the Hogsmill catchment to fix the pollution issues.

This plan needs to show projects that deliver in the next 1-3 years not in 25. If it’s smart sewers, great let’s see the data and the plan.
 
But, as Thames Water’s primary motivation is profit, not clean rivers, we shouldn’t be under any illusion that getting them to do this is going to be easy.
 
Please feel free to feedback your suggestions and comments.
 
Thank you for reading and caring.

And please feel free to keep sharing the petition.

Every signature ups the pressure on Thames Water.

Very Best Wishes
 
Mark Todd