Friends of the Dart – September 2025 Data Review 

Executive Summary 

This report presents a summary and analysis of E. coli monitoring conducted by Friends of the Dart between March and September 2025 across the River Dart catchment. The monitoring  programme forms part of Phase 3 of Friends of the Dart’s ongoing citizen science initiative,  designed to identify pollution sources, track changes over time, and provide a robust evidence  base for action on water quality. Data from the Environment Agency and South West Water has  also been analysed to provide a comprehensive overview of bacterial loading within the  catchment. 

Findings indicate that several monitored tributaries consistently contribute high E. coli concentrations to the main River, particularly the Stoke Gabriel Stream, River Hems, Malt Mill  Lake, and the Bidwell Brook. Median E. coli concentrations at sites on these tributaries  frequently exceeded the Environment Agency threshold for “poor” bathing water quality. In  contrast, other tributaries such as Old Mill Leat, Rattery Stream, Old Road 1 and 2, and the  Harbourne exhibited lower median concentrations, but higher variability associated with  rainfall events. Dartington Beach, Dartington Pontoon and Steamer Quay had consistently  elevated E. coli concentrations, as did sites around Staverton STW and Still Pool. Considering  the popularity of these sites amongst River users, this highlights the importance of continued  monitoring and identification of pollution sources.  

The findings from March–September monitoring provide a strong evidence base for refining  Friends of the Dart’s approach through the winter months. The next phase of work will focus on  identifying pollution sources within high-risk tributaries—particularly the River Hems and Malt  Mill Lake—through targeted sampling and walkover surveys in collaboration with the  Environment Agency and local landowners. Friends of the Dart will continue to sample  Community-Designated Bathing Sites and Steamer Quay twice monthly under both dry and wet  conditions, whilst the sampling frequency of Holne Weir, Stoke Gabriel, Dittisham and Warfleet  Creek will be reduced to once per month, reflecting their consistently low bacterial loads.  Additional sites with lower average E. coli concentrations but high variability will be included in  wet weather sample rounds to better understand the effects of rainfall and runoff on bacterial  loading at these sites.  

This refined winter sampling strategy will prioritise the most affected sub-catchments while  maintaining essential long-term monitoring. Together, these actions will strengthen the dataset  ahead of the 2026 bathing season, support engagement with regulatory partners, and help  protect the health of the River Dart and its tributaries year-round.

Table of Contents  

1. Introduction  

1.1 Introduction to Friends of the Dart 

1.2 Phase 3 Monitoring  

1.3 Friends of the Dart Monitoring Methods 

1.4 Environment Agency Monitoring Methods 1.5 Purpose of This Report 

2. Sampling Site Overview 

3. Site-Level Analysis 

3.1 Main Dart Sites 

3.2 Mardle, Ambrook and the Hems 

3.3 Old Mill Leat 

3.4 Bidwell Brook 

3.5 Malt Mill Lake 

3.6 River Harbourne 

3.7 Stoke Gabriel Stream 

4. Tributary-Level Analysis 

5. South West Water EDM 2025 Analysis 

6. Recommendations and Next Steps 

6.1 Targeted Investigations of High-Risk Tributaries 6.2 Core Monitoring on the Main Dart 

6.3 Wet Weather Sampling 

6.4 Summary of Revised Winter Sampling Strategy 7. Supplementary Material

1. Introduction  

1.1 Introduction to Friends of the Dart 

Friends of the Dart is a Community Interest Company (CIC) working to protect the River Dart  through science, advocacy, and collaboration. One of our key activities is monitoring the River’s  water quality to understand pollution levels and guide our campaigning efforts. Since  launching, Friends of the Dart has helped drive significant change. Our campaigning  contributed to the designation of four Bathing Water Sites along the River Dart, and our data  and advocacy placed pressure on South West Water to commit to 16 infrastructure upgrades  within the Dart catchment. We are also proud to have supported other community groups in  establishing bacterial monitoring on their own rivers, and we work closely with a range of  partners, including the Environment Agency, South Hams District Council, DEFRA, the  University of Plymouth, the University of Exeter, the Bidwell Brook Partnership, the River Dart  Catchment Partnership, and local communities and businesses. 

1.2 Phase 3 Monitoring 

In 2025, we entered Phase 3 of our water quality monitoring programme. This phase builds on  work initiated in 2024 and continues our commitment to sharing open-source, accessible, high quality water data with the local community, partner organisations, and stakeholders. Phase 3  aims to investigate faecal pollution sources, with a particular focus on the Dart’s tributaries, to  better understand where bacterial levels are elevated and why. This work is carried out in  collaboration with partners including the Environment Agency, the University of Plymouth, and  the Bidwell Brook Partnership. 

By conducting weekly monitoring of 30 sites across the Dart catchment, this phase seeks to  answer the following questions: 

● Where in the Dart catchment are pollution levels highest? 

● Do certain tributaries contribute more to bacterial loads in the main River? ● How do rainfall events affect pollution levels across the sites? 

● Is there evidence of continuous pollution sources, such as sewage treatment works or  agricultural runoff, contributing to water quality issues? 

1.3 Friends of the Dart Monitoring Methods 

We test for Escherichia coli (E. coli), a common faecal indicator organism that lives in the  intestines of warm-blooded animals, including humans, and is shed in faeces. Its presence in  river water indicates recent contamination by faecal matter, which may carry harmful  pathogens posing risks to both human and ecological health. Water samples are collected  twice per month at each monitoring site — once under dry weather conditions and once under 

wet weather conditions. These data help us address the questions outlined in Section 2.2. We  use Neogen Petrifilm™ E. coli Count Plates to test for E. coli, a reliable indicator of faecal  contamination from sewage or livestock. If present, E. coli produces blue colonies on the plate,  which are counted to estimate E. coli concentration in colony-forming units per 100 ml (cfu/100  ml). 

Petrifilm plates are ideal for wide-scale environmental monitoring: they do not require a full  laboratory setup, produce results within 24 hours (compared to 48 hours or more for traditional  laboratory tests), and are cost-effective, allowing frequent and repeated testing. To ensure the  continued reliability of our E. coli data, we carry out quarterly validation using results from an  accredited laboratory. A subset of samples is processed in-house using Petrifilm plates, while  duplicate samples are analysed by the laboratory using traditional culture-based methods. 

1.4 Environment Agency Monitoring Methods 

This report considers data from the Environment Agency’s water quality monitoring on the Dart,  which uses traditional culture methods to calculate the E. coli concentration in water samples.  

1.5 Purpose of this Report  

This report provides a review of E. coli monitoring data collected by Friends of the Dart between  March and September 2025, alongside Environment Agency data gathered between May and  September 2025. 

The purpose of this report is threefold: 

1. To summarise and interpret data gathered across the Dart catchment during this  period, identifying patterns, trends, and pollution hotspots. 

2. To inform decision-making by Friends of the Dart directors regarding priority areas for  further investigation and the design of the upcoming winter sampling strategy. 

3. To communicate findings to the wider community, offering an accessible overview of  water quality conditions in the River Dart and its tributaries, and highlighting where  collective action may be most needed. 

The report draws on data collected from monthly sampling under both wet and dry conditions  at sites distributed throughout the Dart catchment. It presents summary statistics and rankings  for each site, compares tributary contributions, and visualises spatial and temporal patterns in  E. coli concentrations. Together, these analyses provide insight into the water quality of the  River system and establish an evidence base for focused monitoring and remediation efforts  through the winter and beyond.

2. Sampling Site Overview 

Friends of the Dart has been monitoring 30 sites across the Dart catchment since March 2025 (Figure 1). These include community-designated sites — areas that, while not officially  designated Bathing Waters, are popular for swimming and other recreational activities. Regular  monitoring of these sites helps to build a clearer picture of water quality and supports other  organisations, such as the Environment Agency, in guiding their own monitoring efforts. These  sites are Holne Weir, Dartington Beach, and Dartington Pontoon. 

Friends of the Dart also monitor officially designated Bathing Water Sites outside of the bathing  season (May–September, during which the Environment Agency undertakes weekly sampling).  Monitoring these sites year-round helps to understand seasonal variation, as the River is used  recreationally throughout the year and access to up-to-date water quality information remains  

vital. These designated Bathing Water Sites are Steamer Quay (Totnes), Stoke Gabriel,  Dittisham, and Warfleet Creek (Dartmouth). 

In addition, Friends of the Dart regularly monitor a network of tributary sites to better  understand the sources and drivers of pollution across the catchment. Data gathered from  these sites support investigations into the key questions outlined in Section 1.2. 

The Environment Agency monitors 14 sites during the bathing season, including the designated  Bathing Water Sites and several tributaries feeding into the River Dart thought to influence  water quality at those bathing locations (Figure 1).

Figure 2. Map of the Dart catchment monitored by Friends of the Dart (red pins) and the  Environment Agency (yellow pins). Numbers associated with the pins are the median E. coli  concentration in cfu/100ml for that sampling site. The following sites consider data from  Friends of the Dart and the Environment Agency: Broadhempston STW DS; Littlehempston;  Steamer Quay; Stoke Gabriel; Dittisham; Warfleet Creek. Red boxes indicate where the sample  site median E. coli value exceeds the threshold for “poor” bathing water quality as defined by  the Environment Agency (500 cfu/100ml for tidal sites; 1000 cfu/100ml for non-tidal sites). 

3.1 Main Dart Sites 

Analysis of all monitoring sites across the Dart catchment highlights pollution hotspots that  should be prioritised for continuous monitoring this winter, as well as areas along the main  River where E. coli levels are consistently high. Sites along the main Dart showing persistently  elevated E. coli concentrations include those upstream and downstream of Staverton Sewage  Treatment Works (STW), Dartington Beach, and Steamer Quay (Figure 2). 

The summary statistics for Staverton STW upstream (US) and downstream (DS) sites are very  similar (Table 4), and the median E. coli concentration is higher upstream of the treatment  works. This suggests that Staverton STW is unlikely to be the primary pollution source, or that  the outfall may be located at a different point than that shown on South West Water’s (SWW)  WaterFit Live map. Monitored tributaries feeding into the Dart upstream of these sites and  Dartington Beach do not appear to carry bacterial loads sufficient to explain the elevated  concentrations observed at these main River sites. This points to possible contributions from  Kilbury STW in Buckfastleigh, or one of the unmonitored tributaries upstream. 

Steamer Quay has shown consistently high E. coli concentrations throughout the monitoring  period and will likely retain its Environment Agency classification of “poor” water quality for this  bathing season. Median E. coli concentrations at Dartington Pontoon and Totnes Weir are lower  than at Dartington Beach and Steamer Quay (Figure 2; Table 4), suggesting that elevated  bacterial levels at Dartington Beach dilute before reaching Dartington Pontoon. The elevated  bacterial input from the Bidwell Brook also appears to dilute before entering the main River, but  there are pollution inputs between Totnes Weir and Steamer Quay that drive the consistently  high levels observed at Steamer Quay. Potential inputs include the River Hems and Malt Mill  Lake, both of which contribute elevated bacterial loads to the main River (see Section 4,  Tributary-Level Analysis). 

There are nine SWW sewage assets with outfalls between Totnes Weir and Steamer Quay,  including Totnes STW, which recorded 917 spills totalling 301.5 hours between January and  June 2025, and Totnes Town Pumping Station, which recorded 2,143 spills totalling 126 hours  (Table 3; Figure 7). 

3.2 Mardle, Ambrook and the Hems 

Key tributaries of interest include the River Mardle, all sites on the Ambrook, and the Hems,  particularly at Broadhempston STW downstream and Littlehempston. The River Mardle receives  a SWW discharge upstream (St Luke’s Church CSO), which spilled five times between January  and June 2025 for a total of 4.5 hours (Table 3; Figure 7). This limited spill duration suggests that  elevated E. coli levels here may result from agricultural runoff or other non-sewage sources.

Broadhempston STW ranks ninth among all Dart-related assets, with 14 spills totalling 363.2  hours in 2025 (Table 3; Figure 7). Combined with the lower median E. coli concentration  upstream of the works (Figure 2), this suggests that the STW could be driving the elevated levels  downstream. 

The Ambrook contains outfalls for three SWW assets with high spill frequencies and durations:  Torbryan Pumping Station (4 spills totalling 491.3 hours), Denbury STW (110 spills totalling  147.7 hours), and Ipplepen STW (177 spills totalling 129.7 hours) (Table 3; Figure 7). Elevated E.  coli levels in the Ambrook could therefore be linked to these assets. 

Littlehempston, the most downstream site on the River Hems, has a median E. coli concentration of 2,000 cfu/100 ml (Figure 2), suggesting that the Hems contributes to poor  water quality downstream at Steamer Quay. The following Ambrook sites rank among the  highest E. coli concentrations across all Friends of the Dart and Environment Agency monitoring locations: Tripe’s Copse Stream, Ambrook US, Torbryan Stream, and  Littlehempston (Figure 3). 

3.3 Old Mill Leat 

Median E. coli levels at sites along the Old Mill Leat are generally below the threshold for poor  water quality, except at Wash US and OML DS. Elevated levels at Wash US appear to dilute  downstream, with OML 2 showing a median concentration of 550 cfu/100 ml. However,  concentrations then rise again at OML DS to a median of 1,800 cfu/100 ml (Figure 2). 

As the Old Mill Leat lies outside the catchment of any SWW assets, these elevated levels likely  reflect agricultural runoff, with a faecal pollution source located upstream of OML DS. The  Staverton Bridge site, just upstream of the confluence of the Old Mill Leat with the main Dart,  shows a median E. coli concentration of 700 cfu/100 ml, suggesting that while certain parts of  the Leat have elevated bacterial loads, they do not appear to significantly impact downstream  water quality on the main River. 

3.4 Bidwell Brook 

Environment Agency monitoring on the Bidwell Brook shows elevated E. coli concentrations,  with medians of 1,400 cfu/100 ml at Shinners Bridge and 2,300 cfu/100 ml at Dartington Lodge  (Figure 2). Five SWW assets discharge into the Bidwell Brook: Rattery STW (28 spills totalling  840.3 hours), Dartington School No. 2 CSO (33 spills totalling 425.8 hours), Dartington C CSO  (16 spills totalling 132 hours), and Textile Mill CSO (65 spills totalling 118.4 hours) (Table 3;  Figure 7).

Although E. coli concentrations at Dartington Lodge — the site nearest the confluence of the  Bidwell Brook and main Dart — are high (2,300 cfu/100 ml), concentrations at Dartington  Pontoon immediately downstream are lower (755 cfu/100 ml) (Figure 2), suggesting that the  Bidwell Brook’s overall contribution to bacterial loading in the main River may be limited. 

3.5 Malt Mill Lake 

Malt Mill Lake was monitored by the Environment Agency throughout the bathing season, with  consistently elevated E. coli concentrations. Whiteley Bridge had a median concentration of  2,000 cfu/100 ml, and Priory Drive 1,600 cfu/100 ml (Figure 2). 

Two SWW CSOs discharge into Malt Mill Lake: Quarry Close CSO (14 spills totalling 9.5 hours)  and St John’s Terrace CSO (10 spills totalling 2 hours) (Table 3; Figure 7). A third CSO, Lower  Collapark, also discharges into Malt Mill Lake, but WaterFit Live reports its last spill as  occurring on 24/10/2024, and it is not listed in SWW’s 2025 EDM dataset. 

Given the low spill frequency and duration of these assets, they are unlikely to be solely  responsible for the high E. coli levels observed. Environment Agency discharge permit data  indicate two additional outflows to the stream — one agricultural and one trade-related. A  targeted winter walkover survey is recommended to investigate these discharge locations and  determine whether they are contributing to the consistently elevated E. coli levels observed  throughout the bathing season. 

3.6 River Harbourne 

Monitoring by Friends of the Dart on the River Harbourne shows a median E. coli concentration  of 1,000 cfu/100 ml, which dilutes to around 600 cfu/100 ml at Bow Bridge on the tidal Bow  Creek (Figure 2). Several sewage treatment works discharge into the Harbourne and Bow Creek  system, including Harbertonford STW, which ranked as the worst-performing Dart asset in  terms of spill duration for 2025 (14 spills totalling 1,465.7 hours). Other relevant assets include  Harberton STW (60 spills totalling 41.8 hours), Ashprington STW (29 spills totalling 11.7 hours),  and Cornworthy STW (69 spills totalling 491.8 hours) (Table 3; Figure 7). 

Given the high frequency and duration of spills in this catchment, it is likely that regular dilution  from tidal flows in Bow Creek reduces their impact on bacterial load in the River. Continued  monitoring is recommended to confirm this.

3.7 Stoke Gabriel Stream 

The unnamed stream rising in Collaton St Mary and flowing through Yalberton before entering  Mill Pool at Stoke Gabriel was monitored by the Environment Agency throughout the bathing  season. The upstream Tor Park site showed extremely high median E. coli concentrations of  8,500 cfu/100 ml (Figure 2), ranking as the most polluted of all sites monitored by Friends of the  Dart and the Environment Agency (Figure 3). 

Downstream, Byter Mill recorded a median concentration of 1,160 cfu/100 ml, while the  sampling site on the main Dart averaged 55 cfu/100 ml (Figure 2). The Tor Park site is located  immediately downstream of the Tor Park Pumping Station, which recorded 13 spills totalling  28.8 hours between January and June 2025. Other relevant SWW assets include the Scout Hut  CSO (21 spills totalling 303.3 hours) (Table 3; Figure 7), located downstream of Tor Park and  Byter Mill but upstream of the Stoke Gabriel sampling point. 

Finally, the Stoke Gabriel Pumping Station, situated just above the Stoke Gabriel sampling site,  was reported on WaterFit Live as last spilling on 29/08/2025, confirming activity this year.  However, it does not appear in the SWW 2025 EDM dataset. It is possible that it did not spill  during the January–June reporting period, but an Environmental Information Request (EIR) was  submitted by Friends of the Dart on 15/09/2025 to confirm this.

Figure 3. Median E. coli concentrations in cfu/100ml of all sampling sites monitored by Friends  of the Dart and the Environment Agency. Medians have been calculated from all available  monitoring data under both wet and dry weather conditions.

4. Tributary-Level Analysis 

Figure 4. Summary of the bacterial loads of each of the Dart tributaries monitored by Friends of  the Dart and the Environment Agency. Tributaries are highlighted in blue. The sampling site  closest to the tributary confluence with the Dart are pinned in red. “Median” refers to the  median E. coli concentration in cfu/100ml of all samples within the tributary. “Above 1000”  refers to the percent of samples within the tributary that exceed the threshold for “poor”  bathing quality (defined here as 1000 cfu/100ml for all tributary sites). “Median at confluence”  refers to the median E. coli concentration in cfu/100ml at the sampling site closest to the  confluence. Where “Median at confluence” does not appear, only one sampling site exists on  that tributary, so the “Median” value represents our best understanding of the bacterial load of  the tributary. 

Tributary-level analysis was carried out using all available data from sites monitored by Friends  of the Dart and the Environment Agency. Median E. coli concentrations were calculated for  each tributary based on all sampling sites within its catchment. 

The Stoke Gabriel Stream contributed the highest bacterial load to the main River, with a  median E. coli concentration of 2750 cfu/100 ml and 75% of samples exceeding the threshold  for “poor” bathing water quality (Figure 4). The River Hems also showed consistently high  bacterial levels, with a median of 1900 cfu/100 ml and 69.9% of samples above the “poor”  threshold. Similarly, Malt Mill Lake had a median concentration of 1800 cfu/100 ml, with 73.7%  of samples exceeding the “poor” threshold. 

The Bidwell Brook exhibited a median concentration of 2000 cfu/100 ml, with 69.2% of samples  exceeding the threshold for “poor” water quality, while the River Mardle recorded a median of  1050 cfu/100 ml and 50% of samples above this level. The remaining tributaries—Old Mill Leat,  Rattery Stream, Ashburn, Old Road 2, River Harbourne, Old Road 1, and Staverton Village—had  median concentrations below the “poor” threshold (Figure 4). 

Examining the median E. coli concentrations at the sampling sites closest to each tributary’s  confluence with the main Dart identifies the following as key tributaries of concern: the Bidwell  Brook (2300 cfu/100 ml), River Hems (2000 cfu/100 ml), Malt Mill Lake (1600 cfu/100 ml), Stoke  Gabriel Stream (1160 cfu/100 ml), and River Mardle (1050 cfu/100 ml) (Figure 4). These  tributaries are therefore likely to contribute to elevated bacterial levels along the main River. 

Analysis of overall summary statistics shows that several tributaries have high mean E. coli values and large coefficients of variation (CV), indicating substantial temporal variability and  occasional high-concentration events that raise the mean above the median. Tributaries  showing this pattern include the Old Mill Leat, Rattery Stream, Ashburn, Old Road 1 and 2,  Staverton Village, and the River Harbourne (Table 5). This variability suggests that E. coli concentrations in these systems are strongly influenced by rainfall, with spikes occurring under  wet weather conditions. Continued monitoring after rainfall events is therefore recommended  to better understand the bacterial loads contributed to the main River by these tributaries after  wet weather events.

Figure 5. Distribution of E. coli concentrations in cfu/100ml of samples taken from each  monitored tributary in the Dart catchment, represented in a boxplot using a log10 scale.  Available data from Friends of the Dart and the Environment Agency are considered here. 

Figure 6. The percentage of samples taken from each monitored tributary in the Dart catchment that exceeded the threshold for “Poor” bathing water quality for non-tidal sites as defined by the Environment Agency (1000 cfu/100ml). Available data from Friends of the Dart and the Environment Agency are considered here.

5. South West Water EDM 2025 Analysis

This section presents analysis of Event Duration Monitoring (EDM) data for 2025 across the River Dart catchment. EDM records start and stop time of storm overflow discharges from Sewage Treatment Works, Pumping Stations, and CSOs. Data source was the SWW 2025 EDM Start Stop Storm Overflows XLS, available to download at:

https://www.southwestwater.co.uk/environment/rivers-and-bathing-waters/waterfitlive/storm overflow-map. The analysis aims to identify the highest impact assets by both frequency and duration of spills. Number of spills refers to the total number of spill events recorded in the monitoring period (January to June 2025 at the time of analysis), and spill duration refers to the cumulative hours of discharge over the monitoring period. All analysis was performed in RStudio. Spills with a duration ≤ 1 minute were presumed to be sensor errors and thus removed from the dataset prior to analysis.

The key findings are that Harbertonford STW was by far the poorest performing asset when considering spill duration (1465.7 hours), followed by Scorriton STW, Rattery STW, and Kilbury STW (Table 3; Figure 7A). In terms of number of spills, Totnes Town Pumping Station far exceeded other assets, recording 2143 spills between January and September 2025. Totnes STW and Mayors Avenue Pumping Station in Dartmouth also appear to be performing poorly, with 917 and 764 spill events recorded respectively (Table 3; Figure 7B). Further analysis of spill events per month revealed that peak spill activity occurred in January and February 2025 for the majority of assets. This may reflect increased rainfall events, however additional analysis comparing spill events to rainfall records is required to confirm this.

Table 3. The total spill duration (hours) and number of spills of all South West Water assets in the Dart catchment for which data is available. The monitoring period runs from January to June 2025. All spills with duration ≤ 1 minute were assumed to be sensor errors and removed from the dataset before analysis. Assets are ranked from highest to lowest considering spill duration.

Overflow Name Spill Duration (hours) Number of Spills

Harbertonford STW 1465.7 14

Scorriton STW 890.2 98

Rattery STW

840.3

28

Kilbury STW

693

95

Holne STW

627

53

Cornworthy STW

491.8

69

Torbryan Pumping Station

491.3

4

Dartington School No2 CSO

425.8

33

Broadhempston STW 363.2 14

Scout Hut CSO

303.3

21

Totnes STW

301.5

917

Princetown STW

239.2

64

Blackbrook North CSO

207.1

84

Denbury STW

147.7

110

Dartington C CSO

132

16

Ipplepen STW

129.7

177

Totnes Town Pumping Station

126

2143

Textile Mill CSO

118.4

65

Pear Tree Cross CSO

117.6

267

Stonepark Crescent CSO

95.8

46

Dittisham Main STW

90.6

61

Smith Street CSO

79.3

128

Townstal Tank CSO

71.7

8

Ferry Boat Pumping Station

51.1

350

Harberton STW

41.8

60

Bridgetown Steamer Quay CSO

40.9

36

Mayors Avenue Pumping Station

40.2

764

Staverton STW

40

6

Lower Ferry Pumping Station

33.5

33

Tor Park Pumping Station

28.8

13

Swallowfields CSO

28.6

29

31 Fore Street CSO

16.8

42

Ashprington STW

11.7

29

Quarry Close CSO

9.5

14

Mill Creek Pumping Station

8.4

6

Widecombe STW

7

12

Old Woollen Mill CSO

6.7

12

Darthaven Marina Pumping Station

4.9

84

Shinners Bridge CSO

4.9

9

St Lukes Church CSO

4.5

22

Kiln Road Pumping Station

3.6

5

St Katherines Way CSO

3.4

15

St Johns Terrace CSO

2

10

………SWW GRAPHS HERE

Figure 7. South West Water assets in the Dart catchment for which 2025 EDM data is available  ranked by (A) Total Spill Duration; and (B) Total Number of Spills. The monitoring period runs  from January to June 2025. All spills with duration ≤ 1 minute were assumed to be sensor errors  and removed from the dataset before analysis. Assets are ranked from highest to lowest  considering spill duration. 

6. Recommendations and Next Steps 

The findings from Friends of the Dart and the Environment Agency monitoring highlight key  areas of concern and provide a strong evidence base for designing the winter sampling  programme. The next phase of work should build on these results to refine understanding of  pollution sources and strengthen the dataset ahead of the 2026 bathing season. 

6.1 Targeted Investigations of High-Risk Tributaries 

Monitored tributaries with consistently high or highly variable E. coli concentrations— particularly the Stoke Gabriel Stream, River Hems, Malt Mill Lake—should be prioritised for  focused winter sampling. Investigations should aim to identify specific pollution inputs within  these catchments, such as failing infrastructure, misconnections, or diffuse sources linked to  land use. Targeted investigations should take place in the form of walkover surveys.  Coordination with local landowners, the Environment Agency, and South West Water will be  important to ensure findings can inform remedial action. Continued monitoring of the Bidwell  Brook is recommended once the University of Plymouth finishes their data collection in Spring  2026.  

6.2 Core Monitoring on the Main Dart 

The following Community-Designated Bathing Sites on the main River should continue to be  monitored twice per month under wet and dry conditions: Still Pool, Dartington Beach and  Dartington Pontoon. The same sampling frequency is also recommended for Steamer Quay.  This reflects the high usage of these sites by people interacting with the River, and the high  bacterial concentrations evidenced in this data review.  

Holne Weir and the following Designated Bathing Sites: Stoke Gabriel; Dittisham; Warfleet  Creek, should be monitored at a lower frequency of one sample per month, reflecting the  consistently lower bacterial concentrations evidenced. This will ensure continuity in the long term dataset and help assess whether interventions or seasonal changes are influencing  bacterial levels. 

6.3 Wet Weather Sampling 

Given the evidence that some tributaries show sharp increases in E. coli concentrations  following rainfall, targeted wet weather sampling should be expanded to cover non-priority  sites. This will support better understanding of how storm overflows, surface runoff, and  agricultural activity impact water quality. Recommended wet weather sample sites are: Rattery  Stream, Old Road 1, Old Road 2, and Staverton Village.

6.4 Summary of Revised Winter Sampling Strategy 

In conclusion, the recommendations are that the following sites continue to be monitored twice  per month under both dry and wet weather conditions: 

- Mardle  

- Ashburn  

- Wash US 

- OML DS 

- Broadhempston STW US and DS 

- Tripes Copse 

- Torbyran Stream 

- Ambrook US and DS 

- Littlehempston  

- Staverton Bridge 

- Still Pool 

- Dartington Beach  

- Dartington Pontoon  

- Steamer Quay 

- River Harbourne 

- Bow Creek 

The following sites should be monitored at a reduced frequency of once per month, aiming to  capture E. coli concentrations under both dry and wet weather conditions: 

- Holne Weir 

- Stoke Gabriel 

- Dittisham 

- Warfleet Creek 

The following sites should be monitored once per month under wet weather conditions only: 

- Rattery Stream 

- Old Road 1 

- Old Road 2 

- Staverton Village 

Together, these next steps will ensure that Friends of the Dart continues to build a strong  evidence base to guide action on water quality, inform engagement with regulatory partners,  and help protect the health of the River Dart and its tributaries year-round.

7. Supplementary Material  

Table 4. Summary statistics for all monitoring sites in the Dart catchment, considering data  from Friends of the Dart and the Environment Agency. E. coli concentrations are in cfu/100ml.  Analysis for Broadhempston STW DS, Littlehempston, Steamer Quay, Stoke Gabriel, Dittisham,  and Warfleet Creek combines Friends of the Dart and Environment Agency data. Standard  deviation is abbreviated to “SD”; coefficient of variation is abbreviated to “CV”, and the  

percentage of samples exceeding the threshold for “poor” water quality is abbreviated to “%  Exceeding Poor”.

TABLES TO FOLLOW HERE……