Here’s the response from Thames Water
I understand that there are several locations in the Hughenden Valley that are at risk of flooding in wet winters. The response you have received via Twitter is correct in that this is as a result of rainfall which has caused elevated groundwater levels. The groundwater then infiltrates into the sewers which, when at capacity, will surcharge and cause localised flooding.
This is not a situation that we are happy with and our CEO, Sarah Bentley has openly stated that ‘…putting untreated sewage into rivers is unacceptable to us, to our customers and to the environment. That is both my personal position and the considered view of the company, its Board and its shareholders. Eliminating untreated sewage discharges is not going to be quick, or easy, or inexpensive and we will need the continued support of our customers and regulators, as well as extensive collaboration with local communities and other stakeholders, to achieve it.’
As this makes clear, eliminating untreated discharges will take time and needs to be seen as an ongoing process. The regulatory process under which we operate in the water industry requires us to make a case for all additional investment. This is the work that is planned in the current business plan period and which will allow us to include the investment in our business plan for the next period which will run from 2025 – 2030.
The Hughenden Valley is one of a number of areas which suffer from groundwater infiltration in this way and, for each one, we are preparing a groundwater impacted system management plan, setting out the approach that we are adopting which we are publishing on our website as they are produced (Drainage Plans | Regulation | About us | Thames Water).
Unfortunately the GISMP for the Hughenden Valley is not yet available and is not currently programmed for publication until 30th November 2021, reflecting its responsiveness relative to other systems and the relatively large size.
In the meantime, we will continue to utilise interim measures to manage any flooding, such as tankering flows away from the sewers and installation of mobile treatment units to reduce the impact of discharged flows. Nevertheless I understand there was a pollution incident reported on 7th March when a manhole overflowed into the stream. Although minor rag was found, no detriment was witnessed in the river.
Responsibility for notifications of any elevated risk associated with the river would normally fall to the local authority rather than ourselves. However where local groups are concerned that no action has been taken we are willing to contribute to the production of appropriate signage for the groups to put up, as we have done in other catchments.
I hope that answers your questions and, if you would like to progress activity on signage please come back to me and I will put you in touch with the appropriate contacts.
Head of Environmental Engagement