What South West Water's Dart investigations found, and what they promise

South West Water has produced interim findings from three investigations into pollution in the Dart estuary: one each for the Steamer Quay and Stoke Gabriel bathing waters, and one for the shellfish water around Dittisham. We obtained the reports under the Environmental Information Regulations (request EIR26017) and have read them closely. All three are on our Resources page. This post sets out what they found, what work South West Water has committed to, and where we think the gaps are.

The investigations are required under the Water Industry National Environment Programme, the list of work the Environment Agency sets for each water company. The interim reports were issued between December 2025 and January 2026. Draft final reports are due in December 2026 and the final versions in March 2027.

What the reports found

Both bathing waters were rated Poor in 2025. At Steamer Quay every one of the Environment Agency's 43 samples that year was above the level needed for an Excellent rating, and South West Water puts the risk of failing to reach even Sufficient at 100 per cent. Stoke Gabriel was rated Sufficient in its first year, 2024, and dropped to Poor in 2025. The oyster beds around Dittisham failed the legal shellfish standard in every year from 2020 to 2024, with between 66 and 84 per cent of samples over the limit.

One finding runs through all three reports. On many of the days with high bacteria readings, South West Water's storm overflows had not been spilling: 27 of 43 days at Steamer Quay, 6 of 10 at Stoke Gabriel and 3 of 10 for the shellfish beds. The reports point instead to farming, private sewerage such as septic tanks, and misconnections, where household waste pipes run into surface water drains. Tests that trace where bacteria come from found mostly livestock signals in the River Dart. But they also found a strong human signal in Malt Mill Lake in Totnes on a dry day with no overflows operating, and in the stream above Stoke Gabriel, where the only overflow upstream was not spilling either.

That stream, which feeds the Mill Pool at Stoke Gabriel, is heavily polluted. The Environment Agency recorded 54,000 E. coli per 100ml at Byter Mill in June 2025. The threshold for an Excellent bathing water is 250. Out in the main river channel off Stoke Gabriel, South West Water's own sampling found a median of 90.

What South West Water has committed to

Across the three reports, South West Water has agreed work on 23 storm overflows and one treatment works, all as part of its 2025 to 2030 investment programme. Each has a target and a compliance date. "10 spills a year" means no more than 10 a year on average; "screening" means fitting screens to catch solids.

By 31 March 2027

• Shinners Bridge storm overflow, Dartington: 10 spills a year, plus screening

By 30 April 2028

• Dartington C, Dartington School Two and Textile Mill storm overflows, Dartington: 10 spills a year, screening
• Kilbury treatment works, two storm overflows, Buckfastleigh: 2 significant spills per bathing season, 10 a year, screening
• Kilbury treatment works, final effluent, Buckfastleigh: ultraviolet disinfection

By 31 March 2030

• Totnes: 31 Fore Street, Bridgetown Steamer Quay and St Katherines Way storm overflows, 2 spills per bathing season, 10 a year, screening. St Johns Terrace storm overflow, Totnes treatment works storm overflow and Totnes Town pumping station, 10 spills a year, screening
• Stoke Gabriel: Scout Hut storm overflow, 2 or 3 spills per bathing season (the reports differ), 10 a year, screening. Stoke Gabriel pumping station, 3 spills per bathing season, 10 a year, screening
• Dittisham: Mill Creek pumping station and Dittisham Main treatment works storm overflow, 10 spills a year, screening. Ferry Boat pumping station, 10 spills a year
• Galmpton: Kiln Road pumping station, 10 spills a year
• Dartmouth: Smith Street storm overflow and Warfleet Creek pumping station, 2 spills per bathing season, 10 a year, screening
• Kingswear: Darthaven Marina and Lower Ferry pumping stations, 2 spills per bathing season, 10 a year, screening. Yarrow Bank pumping station, 2 spills per bathing season, screening

The Dartington overflows and Kilbury come first, by 2028. Everything in Totnes and down the estuary is due by the end of March 2030, the last day of the current programme.

It is worth being clear about what these promises mean. They are commitments to outcomes, not to particular engineering, and none of the reports says how each target will be met, whether by extra storage, separating rainwater from sewage, or something else. The spill targets are averages, so a ten-spill limit still allows more in a wet year. The tighter bathing season limits of two or three spills apply only to overflows close to the bathing waters and shellfish beds. Screening catches solids such as wet wipes and sanitary waste; it does nothing to reduce bacteria. The only promise in all three reports that directly cuts the bacteria leaving a works every day is the ultraviolet treatment at Kilbury.

Our three concerns

The overflows that spill most are scheduled last. The storm overflow at Broadhempston treatment works has averaged 152 spills a year, Rattery 134 and Cornworthy 125, with Cornworthy discharging for between 1,000 and 2,700 hours a year. Cornworthy is pencilled in for 2035, and Broadhempston and Rattery for some time between 2035 and 2040. This is because national rules put overflows within a kilometre of a bathing or shellfish water first, whatever their record. Quarry Close in Totnes, Staverton and Tor Park are down for 2040.

The treated sewage these works release every day. Apart from Kilbury, nothing in the reports improves the routine discharge from the smaller works upstream at Broadhempston, Denbury, Ipplepen, Rattery and Staverton. This matters because storm overflows only spill when it rains, but a treatment works discharges all the time, in dry weather as well as wet. Standard treatment removes most of the solids and organic matter, but it is not designed to disinfect, so the effluent still carries faecal bacteria into the Hems, the Dart and their tributaries. South West Water's own figures show the difference disinfection makes. Totnes treatment works has ultraviolet treatment, its final effluent averaged 28 E. coli per 100ml between 2015 and 2023, and the Steamer Quay report describes its bacteria levels as frequently low. That is why Kilbury is getting the same treatment. The smaller works upstream have nothing comparable.

Timing makes this worse. Flows in the Dart are at their lowest from July to September, when most people are swimming and paddling, so there is less water to dilute whatever the works release. The Steamer Quay report notes that the bathing water can be poor after very little rain, which South West Water reads as a sign of "consistent background sources". It also says the contribution from Broadhempston, Denbury, Ipplepen, Staverton and Rattery "require further understanding". Yet none of these works is part of the investment the reports commit to. Until their contribution is measured we cannot rule them in or out as part of the reason Steamer Quay fails, and if they do turn out to matter, the earliest fix would come in the next investment period after 2030.

The biggest sources sit outside the programme. On South West Water's own evidence, overflows were not operating on many of the bad days. Even if every commitment is met on time, the sources the reports themselves consider most important, septic tanks, misconnections and farm runoff, sit outside the programme. The reports say the planned work "may benefit" bathing water quality, and they go no further than that.

What happens next

The investigations do not commit to anything beyond the list above. Their conclusions feed into the next price review, which sets water company investment for 2030 to 2035, so the draft final reports due this December are where the case for more can be made. Two of the reports name the Harbourne, the Wash, Bow Creek, Mill Creek and the East Cornworthy stream as gaps in South West Water's evidence, and the Stoke Gabriel report says it will review Friends of the Dart data. We plan to send our 2026 sampling results to South West Water and the Environment Agency, including our boat survey between Steamer Quay and Gurrow Point, and we will report back on the response.

If you live in the Dart catchment and rely on a septic tank or small treatment plant, our householder events in October and November are a good place to find out what you can do.