Friends of the Dart has found evidence of illegal dry spills in 14 different areas of the River Dart dating from 2021 to 2023, the worst of which occurred in Rattery where a total of 15 hours of sewage was found to have been released into the river.
What is a Dry Spill?
A dry spill refers to the illegal discharge of untreated or partially treated sewage into water bodies during dry weather, when there has been no significant rainfall to explain the overflow. Water companies are permitted to use storm overflows when sewers become inundated with water due to heavy rain. They are not, however, permitted to discharge sewage into public rivers when there has been no rainfall.
What is happening in Rattery?
The release of sewage in Rattery for a total of 15 hours is alarming for several reasons, primarily because it suggests that the local system is not fit for purpose. Despite assurances of infrastructure improvements, sewage spills appear to be worsening, which is especially worrying given the absence of rainfall to explain them.
Dry spills are particularly concerning because they indicate a direct release of sewage without the mitigating effect of rainwater dilution, leading to higher concentrations of pollutants like bacteria, chemicals, and nutrients in rivers. This can have serious consequences for water quality, aquatic life, and public health, as these discharges can make rivers unsafe for wildlife and humans.
The analysis carried out by Friends of the Dart covers a 3 year period, but by looking at the data we can see that Rattery had no sensor in 2021, so it is impossible to know how many more spills occurred in that time. There were big spills in both 2022 and 2023, unfortunately we have no data for the previous year.
What action is Friends of The Dart taking?
We have contacted South West water for comment and so far have not received a response about the spills or about our method. We will continue to follow-up to understand the reasons for these spills and actions they will take to prevent this in the future.
Friends of the Dart have begun their phase two testing programme which includes high quality lab testing of bacteria in the river from source to sea. We will add the analysis of chemicals to this programme. This testing is running year-round, and the results are posted to our website along with other partner platforms.
| What action can you take? We have also recently launched a Crowdfunder to raise funds for testing, community outreach and other projects that will help us to eradicate sewage in the Dart once and for all. |
| Your donations will enable us to open up even more River for you to enjoy, giving everyone clear information about bacterial content. Ultimately, that’s the equivalent of opening up 1500 olympic-sized swimming pools end to-end, for us all to safely enjoy! |
In cases where sites are being investigated, one criteria considered is the number of ‘justified public complaints to water companies, local authorities or the Environment Agency’. If you live close to one of these sites and have noticed problems, please make a formal complaint (and let Friends of the Dart know). In the event of visible pollution in the water please take photographs, note the time and date and call the Environment agency hotline on 0800807060.
Join the friends of the Dart movement, support your river by registering for our newsletter updates and following us on social media. Spread the word and tell your community, friends and family.
Method for Evidencing Dry Spills
Concerned about an increase in sewage spills, and an apparent deterioration in water quality, Friends of the Dart have previously requested data on combined sewage overflow (CSO) release data from South West Water as part of our efforts to engage with them in a constructive manner.
Sadly South West Water have not responded to this request. We instead made a Freedom of Information request to the Environment Agency for combined sewage overflow (CSO) release data for every South West Water Discharge in 2021, 2022 and 2023. The data consisted of the name of the CSO discharging, as well as the start time and end time of the discharge.
To identify dry periods, rainfall records were downloaded from the Defra Hydrology data explorer for the 7 rain gauges within the Dart catchment.
These are: Austins Bridge, Bellever, Brixham, Dartmoor, Harbertonford, Holne and Princetown.
To identify dry spills, a dry period was considered as 4 consecutive days with no rain in the Dart catchment. This method is in line with the one developed by the BBC (Stallard et al. 2024).
By defining a dry period as four consecutive dry days there is considerable allowance for run off to drain out the system, it is also a more conservative than the method used by the Environment Agency (Environment Agency 2024) when classifying dry spills. The Environment agency classifies a dry spill as one that occurs when there is less than 0.25mm on that day and in the preceding 24 hours. Therefore, in this study, spills have only been classified as dry spills when there have been four consecutive days with less than 0.25mm of rainfall. All dry spills identified that were less than one minute in duration have also been removed on the basis they could be sensor errors.
The full data analysed by Friends of the Dart in relation to dry spills in the River Dart has been broken down into number of spills, total spill duration (in both seconds and in hours and minutes) and average spill duration (in both seconds and in hours and minutes).
For the three year period for which we have data, our analysis shows that the longest dry spills occurred in Rattery, where they were recorded for a total period of 15 hours.
