In April 2026 we asked people to send our information request to Thames Water asking them to publish the details of the first 10 storm (sewer) overflows they planned to upgrade. The company responded on the 19th of May 2026.
In summary Thames Water said:
They don’t have a final list. They are planning to upgrade 17 sites across the whole region by the end of 2027. They have not decided whether they will proactively publish their detailed plans when they are finalised.
A key part of the first request is to put Thames Water on the record. We have a better understanding of its position. It also helps frame the next steps. We are also now in a dialogue with Thames Water and that is productive. They may not like it, but the law gives us this right. I have reflected on the company’s replies below in black. Their replies are below the reflections, in brackets.
The next stage of the campaign will be to send regular information requests to discover when the detailed plans etc have been finalised. At that point we will request that they are published on their website. If Thames Water refuses, we will start the legal process that leads to an appeal to the Information Commissioner’s Office to overrule the company.
We will also start to focus on the condition of Thames Water’s wastewater network. Because it has not been adequately maintained there are pipes leaking into the surface water network and polluting rives with raw sewage. Thames Water thinks it would have to spend £19bn to bring the network up to standard. Ofwat wasn’t convinced that the company actually knew where needed to be maintained in enough detail (Thames Water has admitted before that in some places it has only mapped up to 60% of its network). Many of these sources of pollution could be more damaging than some of the sewer overflows it wants to upgrade. We will press Thames Water to reveal how much/little it does know. This is the first step in getting them to take maintenance more seriously and invest our money effectively. There is an overriding interest in knowing the true state of the assets that taxpayers might be forced to bail out. We are also worried that Thames Water won’t invest enough in maintenance but in creating new assets as this increases the value of the company and how much it can borrow.
1) Send me a list of the first 10 storm overflows you intend to upgrade in London.
Thames Water has confirmed that the list is not finished. Also, that there are a lot of variables still to be addressed. 17 schemes in the Thames Water region by 2027 is useful information. This should mean that overflows at 17 locations will be cut to 10 per year (the Government target). I assume that remains Thames Water’s target too, but we will have to ask them that. Also, how many are in London? It appears that we are now a long way from the 26 London overflows that were cited just over a year ago. They say that these 17 will be completed by the end of 2027, but this gives them 18 months. I can’t help but be sceptical of this. The company says the list isn’t complete and may change, yet schemes will be constructed in such a short time. However, let’s say this is realistic, then the plans and assessments will have to be finalised within a few months to allow work to begin in time. When they are finalised they should be published. The sentence “This reflects our current planning position and may change as further certainty is gained” means that all of their reply above this is uncertain.
( Thames Water’s answer: At present, Thames Water does not hold a finalised or confirmed list of the “first 10” storm overflows in London that will be upgraded. The Storm Overflow Programme for AMP8 (2025-2030) is still in the planning phase. While we have an emerging delivery plan and expect to deliver a number of storm overflow schemes early in AMP8, the precise sequencing of individual sites remains subject to ongoing development and governance. As a result, the identification and sequencing of individual sites may change as the programme develops. Until individual schemes pass the relevant internal governance gateways, we are unable to confirm a definitive list or order of delivery. However, in the spirit of transparency and engagement, Thames Water can confirm that we currently expect to deliver approximately 17 storm overflow schemes across our whole region by the end of AMP8 (April 2025 to March 2030) Year 3 (i.e. 2027), subject to the considerations above. This reflects our current planning position and may change as further certainty is gained. We also note that references to investment announcements should be interpreted carefully. The figure of approximately £1.6 - £1.8 billion refers to pollution reduction investment across multiple programmes, of which storm overflows form one part rather than being solely attributable to storm overflows.)
2) Publish on your website the detailed assessments for the first 10 storm overflows you intend to upgrade in London. Please include the cost-benefit and other economic analyses and assumptions used to produce these assessments.
The answers to 2, 3, and 4 can be combined.
“As this information has not yet been created, any decisions on whether to pro-actively publish this information on our website have not yet been taken.”
This was going to be their most predictable response as the regulations exempt them if the information does not exist.But this is the first control measure our campaign has introduced – they can’t start upgrades without detailed plans (if they were to then there is a great risk that the investment wouldn’t be value for money). This will make Thames Water do a better job, with more considered options.
We need to focus on “any decisions on whether to pro-actively publish this information on our website have not yet been taken”. It looks Thames Water is going to resist publishing the detailed upgrade plans for sites. It is trying to convince us that it gets to choose to publish the information. But the law doesn’t give them this right. 4.1 of the information regulations says a body shall “progressively make the information available to the public by electronic means which are easily accessible; and take reasonable steps to organize the information relevant to its functions with a view to the active and systematic dissemination to the public of the information.” The Notes for the regulations also say “In these decisions public authorities must apply a presumption in favour of disclosure”.
Further, the Information Commissioner’s Office recommendation to United Utilities regarding proactive dissemination of information:
“Not only should United Utilities assume the majority of the information it holds is environmental, but in line with part II of the EIR Code of Practice, and the Commissioner’s recent letter, it should review its culture around proactive disclosure.”
In its reply, United committed to proactive and effective disclosure in the following way:
“To further improve accessibility and the relevance of published data, we are actively engaging with external key stakeholders to understand what additional information they would find valuable. The includes working collaboratively to identify opportunities to enhance the visibility of important data related to our wastewater performance and water quality. By incorporating this feedback, we aim to make our published information more meaningful, user-friendly, and accessible.”
We are making it clear what additional information we would find valuable. Thames Water obviously considers whether information it holds should be published on its website. There is no point in putting every scrap of it online and it is not expected to. But other information is clearly in the public interest – money being well spent or projects actually addressing the worst sources of pollution. Further, we are helping them to work out which information should be in the public domain by requesting it!
We will use information requests to discover when plans have been finalised. If these are not published on their website then Thames Water is breaking section 4.1 of the law. We can then make a formal complaint to Thames Water and if they refuse to change their position we will appeal to the Information Commissioner’s Office to overturn it.
In answer 4 their statement “However, a public authority does not have an obligation to create information in response to an EIR request” is an odd response. We are not asking them to create information but publish their detailed plans when complete. Re the regulations not providing a right for requesters to request that information be updated – while correct we can use the law to request the most up to date plans. We can use this tactic to make the point that it will be easier to put the information online rather than have to send it to lots of people individually.
(Thames Water’s answer: As explained in our response to Question 1, detailed assessments for a confirmed set of “first 10” storm overflow sites are not yet finalised as the programme remains in development. As this information has not yet been created, any decisions on whether to pro-actively publish this information on our website have not yet been taken. That said, Thames Water does already make publicly available a range of information about its investment planning, performance and expectations through existing publications, such as: Annual regulatory submissions to Ofwat. Our published plans and performance reports, which provide information on programme intent, progress and outcomes at an aggregated level. This information is available via our website: https://www.thameswater.co.uk/about-us/performance/regulatory-library)
3) Publish the Investment Plans for these 10 combined sewer overflow sites in London when they have been completed.
See 2 above.
(Thames Water’s answer As you are aware, under the EIR and ICO guidance, Thames Water has a general obligation to publish, update and add environmental information (policies, plans, procedures, reports and impact studies etc) proactively by easily accessible means, and to take reasonable steps to organise information relevant to its functions to enable it to publish information proactively and systematically. However, as this information has not yet been created, any decisions on whether to pro-actively publish this information on our website have not yet been taken.)
4) Update the above information as changes occur, alongside detailed information (explanations of the considerations, factors, and criteria involved) when investment decisions are made.
See 2 above.
(Thames Water’s answer: Please see our response to Question 3 in respect of Thames Water’s obligations in respect of publishing environmental information. However, a public authority does not have an obligation to create information in response to an EIR request - EIR does not provide a right for requesters to request that information be updated. As a result, we do not believe that Question 4 is a valid request for data under EIR which Thames Water are obliged to respond to.
5) If detailed reasoning has not been recorded for decisions for particular sites, please briefly explain why, as according to the EIR Code of Practice published by the ICO, Thames Water has a duty to take reasonable steps to organize records, which includes records of reasoning.
This question was to gauge how wide their record keeping is. It doesn’t seem Thames Water will have recorded the discussions behind the plan making (e.g. meeting minutes). That’s fine, it’s the finalised plans we want to see. Once we can get them in the public domain independent experts can assess them. Then we will know whether their decision making has been sound.
(Thames Water’s answer: Again, regardless of wider ‘good housekeeping’ principles, there is no obligation, nor is it reasonable to expect, that Thames Water hold in a recorded format a record of why every piece of data has not been updated. Given we expect this information will not be held (and that there is no requirement to create information in response to an EIR request) we also do not believe this question to be a valid request that requires a response under EIR.)