Abstract: In August 2020 I wrote a series of blog entries about why I was getting ill so often from swimming in Poole Harbour. In early November Surfers Against Sewage released a report that showed that Shore Road Beach, Poole Harbour (aka Kite Beach) is the most polluted bathing water in the country, accounting for 10% of the sewage discharges in England and Wales. This article is a compilation of all the data and links that point to how this has escaped general knowledge to date and what can be done to improve the situation.

Updates since this article was published

I sense this list may grow as I peel the layers off this particular onion but..

  • Jan 19th 2020, Express.co.uk "Sewage-filled rivers ‘caused oyster bug’, probe suggests"
    • "A restaurant owned by celebrity chef Rick Stein was one of several caught up in the food safety crisis as diners fell ill after eating shellfish."
    • "The oysters are believed to have come from Poole Harbour and a Dorset-based supplier suspended its sales for 28 days."
    • "A probe by Public Health England has suggested norovirus as the ­suspected cause of the debilitating ­illness, which is not routinely tested in molluscs sold for eating."
    • Rick Stein operates a shellfish restaurant that is located on Poole Harbour, metres away from Shore Road Beach (10 -14 Banks Road, Sandbanks, Poole)
  • Summer 2020 (date TBC)
    • A Poole Harbour Commission meeting revealed that the local shellfish have been downgraded in quality - likely due to the effects of pollution 
  • Nov 9th 2020
    • Wessex Water have agreed to provide BeachPeople with details on all sewage and mixed discharges into Holes Bay in the last 12 months (i.e. the period covered by the SAS report)
    • This will take them between 20 and 40 days
  • Nov 19th 2020
    • The citizens who live near the heavily polluted Mar Menor lagoon in Spain are exploring the idea that the area can be deemed a legal entity in its right and thereby be protected under law.
  • Dec 1st 2020 - BCP Council announce that a £2.7m nature park is to be created to offset the development around Poole Harbour - in particular nitrogen
    • "BCP Council is required to ensure all development in the harbour catchment area is “nitrogen neutral” to protect it from pollution."
    • "Research has found most of it is linked to agriculture but sewage treatment outflows are also contributors, despite technology being in place to limit it."
    • I'm no expert in building but apart from those wonky portaloos and maybe some fertiliser on the little squares of grass I don't think new homes generate much nitrogen on an ongoing basis. Apart from the sewage.. which is a tacit acceptance that houses around the Harbour pollute the water and the solution is a pay a fortune for a field elsewhere.
    • Dorset Wildlife Trust have been emailed for comment
  • Dec 2020 - Surfers Against Sewage announce #EndSewagePollution campaign - over 100 MPs put their name to the bill
  • Dec 1st 2020 - Microbiological testing facilities contacted about the daily testing of the Holes Bay outflow for the presence of raw sewage
  • Dec 2nd 2020 - Environment Agency contacted about water sampling in Poole Harbour
  • Dec 7th 2020 - Wessex Water provide Poole-based BeachPeople.club with the following raw data over the period covered by the SAS report:
    • How many outfalls there are into Holes Bay and their location and type
    • The dates and times of all discharges of untreated sewage into Holes Bay over that period
    • Roughly how many cubic metres of combined rain and untreated sewage was involved in each discharge
    • They note that "Surfers Against Sewage (SAS) produced their Water Quality Report (2020) based on alert notifications received from water companies. This does not reflect when overflows were actually in use. Alert notifications can be triggered several times during one heavy rainfall event when an overflow might be in use. These include on/off alerts and sometimes false alarms. "
    • Email thread and downloadable documents here: Wessex Water: Pollution in Poole Harbour
  • Dec 12th 2020 - Sir Robert Syms, Conservative MP for Poole emailed about the issues
  • Dec 13th 2020 - Extinction Rebellion stage protest about sewage pollution in Christchurch
  • Jan 5th 2021 - Response from the Environment Agency to why the water quality sampling was all but ceased in Poole Harbour in 2020: Environment Agency Explanation of Reducing Water Sampling in Poole Harbour
  • Jan 11th 2021 - Further response from the Environment Agency in which they drawn attention to the Notifications of Storm Overflow use published by Wessex Water (and used by the SAS to compile their reports), and the Agency's own Event Duration Monitoring (EDM) - a process for measuring and recording how often and for how long discharges from storm overflows occur - full transcript appended to the email thread here.
  • Jan 11th 2021 - Sewage Discharge Information for the year to October 31st 2020 re-requested from Wessex Water as data for 2016-2019 was provided
  • Jan 15th 2021 - MP Philip Dunne's Sewage (Inland Waters) Bill due to be read in Parliament

Email threads (subscribers only, regularly updated):

Wessex Water: Pollution in Poole Harbour

Environment Agency Explanation of Reducing Water Sampling in Poole Harbour

Helpful Links

HM Government Permits For Storm Overflows etc.

 - includes a definition of the the 12/24 method for classifying outflow events

HM Government Bathing Water Quality Explainer

 - the UK Bathing Water Quality season is May to September

Sewage pollution in Poole Harbour 2020

On November 6th 2020, Surfers Against Sewage published a Water Quality Report which made for scary reading for anyone that swims in Poole Harbour, as Wessex Water have discharged sewage into the water a total of 299 times in the last year (between October 1st 2019 until September 30th 2020) - accounting for 10% of the 2941 total discharges in England and Wales and three times higher than the next 'Very High Discharge' offender, as this graphic from their report shows:


Fig.1 Sewage Discharge Map from Surfers Against Sewage's Water Quality Report, November 2020

Here's what the SAS report says about the year in general:

“This year, transparency in water quality information has become even more important with the onset of the COVID-19 pandemic and potential transmission risk for viruses in sewage. However, data from our Safer Seas Service (SSS) shows water companies are still discharging sewage at alarming rates, polluting the environment, and risking our health.

Between 1st October 2019 and 30th September 2020, a total of 2,941 Combined Sewer Overflow (CSO) discharge notifications were issued through the SSS, which is based on information we access from water companies.

1,195 of these were issued during the official Bathing Season in England and Wales (May 15th – September 30th) and a further 1,746 were issued out of season by the water companies willing to issue year-round data, in response to the need for more transparency and accountability.”

“UK Bathing Waters suffer the impacts of an extensive network of water company Combined Sewer Overflows (CSOs), emergency infrastructure designed to discharge untreated wastewater during periods of “unusually heavy rainfall”.”


Separately a CEFAS Sanitary Survey report on shellfishing in Poole harbour (PDF) contains useful information on sewage outfall volume and locations but is dated 2009 so may not be considered recent enough to be relevant here.


Water Quality Testing in Poole Harbour

So how has Poole Harbour become so polluted whilst at the same time established itself as an ocean sports mecca? Isn't the water tested regularly?

Well, that's the job of the Environment Agency and if you drill down into the Poole Water Quality links on the BeachPeople.club site you'll quickly see that testing for sewage has recently become sporadic at best (just three times this year compared to twenty or so tests in each year from 2016 to 2019) - here are the results for Poole Harbour Lake:


Fig 2. Environment Agency Bathing Water Tests for Poole Harbour Lake

Update - 5th January 2021 - the Environment Agency have responded as to why they all but ceased conducting bathing water quality sampling in 2020 - see Environment Agency Explanation of Reducing Water Sampling in Poole Harbour

Source of Sewage Pollution in Poole Harbour

According to Wessex Water's website (bolding is mine):

"Sewer network

The Poole area has a predominantly separate sewer system, where wastewater, sewage from homes and businesses, is collected into the foul only sewer and is conveyed to the water recycling centre (WRC). Storm water, rainwater collected from roofs and yards, is collected into a separate surface water sewer which conveys the rainwater to the river. However, in some situations the surface water sewer discharges to the foul sewer. In these cases, under heavy storm conditions, sewer capacity can be exceeded and built in safety valves called storm overflows, permitted by the Environment Agency, can operate to prevent sewer flooding.

Water recycling centre

Wastewater received at Poole WRC is treated under normal flow conditions and are further treated through nitrate removal to reduce the nutrient load discharged to Holes Bay and Poole Harbour. The flows are also disinfected by UV treatment to reduce the bacteria load to the shellfish and bathing waters in Poole Harbour. Under heavy storm conditions, flows into the WRC can exceed its capacity. These excess flows will first overflow to storm storage tanks. If these tanks become full, they in turn spill to Holes Bay as a storm overflow, as permitted by the Environment Agency, having benefited from screening and a degree of settlement within the storm tank. The site also receives trade discharges for treatment through the WRC process."


Location of the Water Quality Sampling Points in Poole Habour

Given that the sewage discharges into Holes Bay - you'd think that the water quality would be sampled in Holes Bay. But no, in the three or four times this year that the Environmental Agency has sampled Poole Harbour water quality this year it has done so at the following locations (harbour test locations highlighted in orange) - from the left: Rockley Park, Poole Harbour Lake, Studland Knoll House, Shell Bay North, Sandbanks Peninsula, Shore Road (but not the Shore Road that is quoted in the SAS report as the SAS location is on the Harbour side; that's currently untested).


Fig 3. Environment Agency Bathing Water Quality Testing Locations Poole Harbour 2020


Here's a closer look at Holes Bay area including Kite Beach, a very popular place for ocean sports:

Fig 4. Detailed Map Showing Environment Agency Sampling Points, Kite Beach Ocean Sports Area and the Holes Bay Sewage Outfall

Fig 4.1 Holes Bay Sewage Discharge Points 

Fig 4.2 Poole Harbour Sewage Discharge Points

So you can see how it's perfectly feasible for a sewage discharge to be timed to join an outgoing tide and miss all the Environmental Agency water sampling points, and even if it didn't the water in the Harbour has only been sampled three or four times in the whole of 2020 so it would be extremely unlikely for it to be recorded. Yet the untreated sewage can still flow into the Kite Beach area (Shore Road, Harbour Side) where 299 cases of sewage discharge were recorded by SAS.

This image from a 2009 CEFAS sanitary study of Poole Harbour shows that during the ebb tide, water is carried from Holes Bay directly to the Shore Road (Kite Beach) ocean sports area and once out of the harbour is taken along the Sandbanks beaches to Canford Cliffs before being turned back by the tide. At that time, 47,700 cubic metres of treated sewage were discharged into Holes Bay every day - the next largest discharge was at Wareham and amounted to 2,500 cubic metres per day. The study notes that:

"Faecal coliform concentrations in the effluent from Poole STW.." [Sewage Treatment Works] "..have increased since 2006. The underlying cause for the deterioration in effluent quality is not known"


Fig 5. CEFAS Tidal Flow Map of Poole Harbour at Peak Ebb


Back to the previous map (Fig 4.) - Shell Bay North (bottom right of the map) would seem to be the ideal point to sample for sewage (I have swum there once - never again - the mud is disgusting) but as you can see from the Environmental Agency's website they have only sampled the water there twice this year and only four times a year since 2016. That stands little chance of catching any pollution instances.


Fig 6. Environment Agency Bathing Water Tests for Shell Bay North Poole Harbour

But the ocean-facing beaches aren't affected, right?

Sandbanks is a long, thin sand peninsula - if you swim from the mouth of Poole harbour north east towards Bournemouth during an outgoing tide you will notice strong warm currents streaming from the ends of a series of rocky groynes along Sandbanks Beach, which suggests there are large harbour outlets that run under the peninsula and help to empty the harbour of water (thereby reducing the strong tidal flow through the mouth of the harbour where the ferry plies its trade).

From the tidal flows link on the BeachPeople Planning page we can see that the tide flows from the North East to the South West after high water, which is fortunate for Poole and Bournemouth beaches as that takes any sewage discharge from Poole Harbour along the Studland coast instead (although there is some swirling along Sandbabks Beach during peak ebb as shown in the blue map, Fig. 5). Not so great for the swimmers off Studland but their numbers are a lot lower.



Fig 7. Poole Harbour Tidal Flow 2 Hours after High Water

What to do about the problem

Looking at the maps in this way it's pretty clear that if you wanted to find pollution then the sampling point would need to be at the outlet of Holes Bay, and if you wanted to protect ocean sports people then the sampling point would be at Kite Beach (ideally at the end of the East Dorset Sailing club pier or North Haven Yacht Club pier as they bracket the kite surfing area).

Equally if you wanted to find pollution then you would sample each day on an outgoing tide, especially after heavy rain. Stormy conditions are when many ocean sports people tend to be out on the water, unlike beach users who prefer the sun.

..but if you didn't want to find pollution then abruptly reducing the water quality sampling rate to twice a year and selecting places as far as you can away from Holes Bay, ideally with rivers flowing into them, would be your best option.

Essentially - an independent bathing water quality monitoring station needs to be established to keep an eye on the actual sewage discharges into Holes Bay (rather than relying on those that are reported by Wessex Water) - look and you shall see.

There might be hope on the horizon, but not anytime soon..

Improved Monitoring

On the 14th July (no year mentioned but I am guessing 2020), an article on the Poole Harbour Commission website announced the following:

"..BCP Council has announced a pilot project which will utilise artificial intelligence (AI) technology to monitor, protect and improve the water ecosystem in Poole Harbour...

The new project will .. provide a network of water quality sensors to continuously monitor the harbour for real-time AI analysis. This innovative, low cost approach to environmental monitoring will enable the detection of a much wider range of physical, chemical and biological indicators within the harbour. This will help them to understand, manage and predict events such as bacterial build up, sewage, fertiliser run-off and industrial discharges, which can be harmful for aquatic ecosystems, creating a build up of algae which can be detrimental to water quality.

The project is commencing with a pilot in the Poole Park lake, which is connected by a sluice channel to Poole Harbour. With more shelter around the lake making it easier to access the AI, the pilot will utilise existing water quality data from the lake to help to train the AI ahead of its use in Poole Harbour."

There was no mention of whether the data will be made public and the location (Poole Park Lake sluice gate) is more for convenient access than demonstrating the existence or otherwise of heavy sewage pollution; this won't yield much value short-term so it seems sensible to rely on proven technology to monitor the sewage levels coming out of Holes Bay.

More Severe Penalties

Without independent and incontrovertible proof, the polluters are able to wait a couple of tides and all evidence is lost – it’s only with hard, reliable data that the private members bill to prosecute polluters being sought by MP Philip Dunne in July 2020 stands a chance of being effective. Mr Dunne says that the bill will "introduce water firms to [the] polluter pays" concept. Next read of the Bill is January 15th 2021.

A rather telling section from the above Guardian article shows the difference between the proactive approach of South West Water and the reactive approach of Wessex Water, who feed into Holes Bay:

"A spokesperson said in 2018-20 South West Water completed an extensive programme to install event duration monitors on its 1,192 overflows.

As a result, more than 90% of these now provide data on the start and stop times of any storm water discharges. Thirty-seven overflows were being investigated in relation to their frequency of operation and potential environmental impact.

Wessex Water said it had categorised its CSOs and the information was shared when requested."

© BeachPeople 2020