Stodmarsh Sewage Crisis: Southern Water, Otterpool Park and East Kent

At Canterbury’s scrutiny committee on 4 March (from1hr 46m 44s onwards), Stodmarsh kept popping up like the blinking red light on a dashboard that everyone hopes belongs to somebody else’s car. It did not. It belonged to the whole East Kent system.

Southern Water’s Paul Blackwell mentioned Stodmarsh when talking about removing phosphorus and nitrogen upstream. Dr Ian Goodall mentioned Stodmarsh when setting out grim evidence on nutrient pollution in the Stour. He also mentioned that the E coli found in the Stour in Canterbury was resistant to last resort antibiotics used to treat E coli. Councillor Alan Bland mentioned Stodmarsh when warning that phosphates have to be cut “all the way down to Stodmarsh”. Different speakers, different angles, same message: this is not a niche conservation footnote. It is the place where East Kent’s sewage, planning and river failures all end up in the same muddy bucket.

And here is the part Folkestone & Hythe residents should not miss. Stodmarsh is not just Canterbury’s headache. Folkestone & Hythe District Council has already admitted, in black and white, that the Stodmarsh problem reaches into this district too. FHDC’s own planning position statement says the Natural England advice applies to development draining to Sellindge wastewater treatment works and adds, bluntly, that for Folkestone & Hythe the implications are “limited to Sellindge WwTW only”. It goes further: development whose wastewater goes to Sellindge is caught by the Stodmarsh issue whether the site is in the Stour catchment or not. That is not us being dramatic. That is the council’s own wording.

That matters because once you translate the planning jargon into English, “nutrient neutrality” means this: if a development will send more nitrogen or phosphorus into a protected water environment already in trouble, the law says the authority cannot just shrug and wave it through. FHDC’s position statement spells that out too. As the “competent authority” under the Habitats Regulations, it says permission can only be granted where there is no adverse effect on the integrity of the protected site and no reasonable scientific doubt remains. In other words, not “we hope it will be fine”, but “we are sure it will be fine”. In East Kent, that is a very awkward standard when the river system is already failing.

And that brings us to Otterpool Park, the council-backed new town that has spent years being sold as visionary, sustainable and practically wrapped in meadow flowers. Natural England’s advice on the scheme was not exactly a valentine. It said Sellindge WwTW had become a named works in the investigation into phosphorus and nitrogen loading affecting Stodmarsh, and stated there was an “impact pathway” from Otterpool Park whether wastewater went via Sellindge or via an on-site treatment works discharging into the East Stour. So even the supposed workarounds came with a large regulatory asterisk attached.

FHDC’s own Otterpool utilities strategy then said the quiet part out loud. It considered the viable wastewater options and concluded that nutrient neutrality issues had influenced the preferred option. Why? Because discharge via Sellindge would result in higher nutrient levels reaching the East Stour than an on-site treatment facility, and because the scale of mitigation needed for the Sellindge route could not be provided within the Otterpool Park boundary. That is about as close as you get in consultant-speak to saying: this option is a problem, the numbers are ugly, and the fix is too big to fit on site.

So FHDC’s answer has not been to pretend Stodmarsh does not matter. Its answer has been to try to engineer around it. Kent County Council’s weekly planning list shows that application KCC/FH/0020/2025 is now before the county council for the erection of a wastewater treatment works, primary substation and integrated constructed wetlands on land at Otterpool Park, east of Harringe Lane and west of Barrow Hill, Sellindge. This is not a vague future aspiration. It is a live planning proposal.

And the history behind it matters. FHDC’s Core Strategy Review said there was only limited capacity in the existing system for the very early phase of Otterpool and that a more holistic wastewater solution was needed. It identified upgrading Sellindge or building an on-site treatment works as the two viable routes, with West Hythe ruled out. It also inserted an extraordinary little footnote on page 114, that deserves far more public attention than it has received: the on-site wastewater treatment works requires a minimum of 400 units to be connected before there is sufficient flow through the works, and before that an interim solution such as tankering off-site or a package treatment works would be needed. Garden town, meet tanker lorry.

This is where the Canterbury meeting suddenly starts to look less like a local scrutiny session and more like a preview of the same film showing further down the coast. In Canterbury, councillors were asking why people still have to check an app before going into the sea. In Folkestone & Hythe, the live infrastructure answer to Stodmarsh appears to be: build a new treatment works, build wetlands, hope the permitting stack works, and get enough homes connected quickly enough that the whole thing starts functioning as planned. That is not exactly the sort of sentence you put on a glossy brochure beside a happy child and a dragonfly.

The larger East Kent picture is just as bleak. KCC’s own committee papers said in March 2024 that nutrient neutrality in the Stodmarsh catchment was having a “significant impact” on housing delivery, with around 7,000 homes then held up in planning and around 30,000 forecast to be affected up to 2040. The same report said many schemes would need either a strategic mitigation option to buy into or significant on-site infrastructure at extra cost. So when Stodmarsh came up in Canterbury, it was not just an environmental issue. It was a planning blockade, an infrastructure bill and a legal headache stretching across district boundaries.

What made the Canterbury exchanges so revealing was that the councillors kept stripping away the euphemisms. Southern Water talked about transparency, intelligence, performance data and live information. Councillors kept dragging the discussion back to the question normal people ask: when can we stop worrying about the water? One councillor put it perfectly: the app is not the answer, clean water is the answer.

Quite.

Because an app is not remediation. It is an admission.

What we are now watching in Folkestone & Hythe is the same crisis in a different suit. Canterbury sees the downstream ecological warning. FHDC sees the upstream planning constraint. Otterpool Park sees the costed engineering workaround. KCC sees a pile of delayed homes and a mitigation strategy. Everyone sees a different part of the elephant. The smell, however, is the same.