Official Responses

Every now and then an organisation will send out an official or full response (rather than the more common emails that bounce to and fro to exchange detailed information) - the two main players in the pollution of Poole Harbour with untreated human sewage are Wessex Water and HMG.

Here are their most recent positions, sent around the time that the Sewage Bill was being bonced back and forth between the Houses of Commons & Lords.

Response from Sir Robert Syms MP

Response from Wessex Water

Separately but still of interest is the Envronment agency's explanation as to why they ceased sampling the water entirely during 2020

Environment Agency's Explanation Of Why They Stopped Sampling Water In Poole Harbour

Response from Wessex Water

Sent Novermber 3rd 2021 by Ruth Barden, Wessex Water and reproduced in full without amendment

Dear Phil,

Thanks for your email and I am pleased that you have found the site visits and information useful.


There has been increasing public awareness, media campaigns and Parliamentary interest in storm overflows in recent weeks and the options for improvement.  Wessex Water is actively engaged in this work, particularly to understand the impact of our assets from both an environmental and public health perspective, and to ensure that any investment in improvements is sustainable.


As you know, we are currently investigating the impact of our assets in Poole Harbour, understanding both nutrient and bacteriological contributions, and comparing these with other sources, to understand where future investment may be required to address this.  The findings of these investigations will inform our next Business Plan which will be submitted to Ofwat in summer 2023.  More information can be found here: 9797.pdf (


Any additional sampling and data collected is always very valuable in understanding the environmental condition of the Harbour and water quality.  We are working closely with BCP, the EA and other stakeholders to share water quality data where available to improve our collective knowledge and understand the actions which each organisation can take to enable improvements.


Wessex Water supports the aspiration for recreational users to apply for designated status of bathing waters where there is the demand and criteria are met.  There are already a number of designated sites within Poole Harbour, both as bathing waters or shellfish waters, and we work will all relevant parties to enable good communication and sharing of data to support these designations.


Storm overflows have always been part of the sewerage network in the UK because the majority of sewers carry both rainwater and foul sewage and they prevent properties from flooding following intense rainfall. We are now getting more intense rainfall storms due to climate change, so this means the frequency of overflow operations will increase.


There are only two possible approaches to eliminating overflows; separation to stop stormwater entering the combined sewer, or constructing large storage tanks, which would have significant carbon consequences, cost billions and would be hugely disruptive.


We need Government to change legislation so developers cannot connect surface water to combined sewers which is making the matter worse. There is also the need for water companies to be able to release rainwater only directly into a watercourse.


Ofwat, the economic regulator, needs to prioritise investment, which it tightly controls to keep bills down, so water companies can get on and help solve the problem.


Since 2000 Wessex Water has invested £181m to improve nearly 600 storm overflows across the region, with a further £150m set aside for improvements between 2020 and 2025.




Kite Beach Poster

This poster will be displayed at surf schools and shops

at Kite Beach from November 2021

Water Sampling at Kite Beach

 BeachPeople is campaigning to have Kite Beach (Whitley Lake) classified as a Bathing Water by Defra so that the water is tested by the EA for evidence of pollution (E.coli etc) 20 times per bathing season.

There are currently only two EA sample points in the whole harbour and both are upstream of the outfalls at Holes Bay which are licenced to discharge 48,000 tons of processed sewage per day and unlimited amounts of untreated sewage during heavy rainfall. (In-depth information collated over the last 12 months can be found at under ‘Articles’).

By sampling at Kite Beach we can start to accumulate incontestable evidence about local pollution levels as well as gauge the state of the harbour’s health in general.

Poseidon will be helping next summer by keeping a tally of the number of beachgoers and ocean sports people in the water but to get it passed we will also need the support of the local authority (BCP), and that’s where you come in.

Generally local authorities only act when it is clear that the issue is important to the local community so, please, when you get a chance – register with us at This email address is being protected from spambots. You need JavaScript enabled to view it..

We aren’t looking for money. Right now we just need to spread the word that this situation can be improved at no cost if local residents demonstrate that this is something they are willing to vote for. BeachPeople and Poseidon will do the rest.

 Kind regards

This email address is being protected from spambots. You need JavaScript enabled to view it.

To The Beach!

Download this poster as an A4 PDF here

Response from Sir Robert Syms MP

Received 28th October 2021 and reproduced in full without amendment

Dear Phil,      There has been much misunderstanding and controversy concerning the Environment Bill as it passes through Parliament.  To be clear: the Bill strengthens controls on sewage outfalls – not weakens it.  But had the amendment stopping all sewage outfalls been passed, it would have resulted in the dangerous discharge of sewage into our streets at times of high rainfall and would have landed customers with unsustainably high water bills.  The amendment proposed by a back bench hereditary Peer had just not been thought through.  The Government has now agreed a form of words that meets the objective that the Amendment was seeking but it worded in a more workable form.  I should stress that the legislative process of a complex Bill does mean the MPs vote on numerous occasions, not for or against sewage, but to find a form of words that make the Bill workable and successful in the objective of cleaning up our rivers and seashore.

The Environment Bill now imposes

  • a new duty on Government to produce a statutory plan to reduce discharges from storm overflows and their adverse impact, and report to Parliament on progress.
  • a requirement for government to produce a report setting out the actions that would be needed to eliminate discharges from storm overflows in England, and the costs and benefits of those actions. Both publications are required before 1 September 2022.
  • a new duty directly on water companies and the Environment Agency to publish data on storm overflow operation on an annual basis.
  • a new duty directly on water companies to publish near real time information on the operation of storm overflows.
  • a new duty directly on water companies to monitor the water quality upstream and downstream of storm overflows and sewage disposal works.
  • a new duty directly on water companies to produce comprehensive statutory Drainage and Sewerage Management Plans, setting out how they will manage and develop their drainage and sewerage system over a minimum 25-year planning horizon, including how storm overflows will be addressed through these plans.
  • a power of direction for the government to direct water companies in relation to the actions in these Drainage and Sewerage Management Plans. We will not hesitate to use this power of direction if plans are not good enough.

In addition, between 2020 and 2025, water companies will invest £7.1bn on environmental improvements in England. Of this, £3.1 billion specifically will be invested in storm overflow improvements.

The age of our Victorian sewerage systems means that the complete elimination of discharges from storm overflows would be extremely difficult. This process would involve the complete separation of sewerage systems, leading to potentially significant disruption for homes, businesses and infrastructure across the country. Initial assessments suggest total elimination would cost anywhere from £150 billion to £600 billion. With such amounts, huge customer bill increases and trade-offs against other water industry priorities would be unavoidable.

Governments – as opposed to opposition parties – do need to take all these factors into account.

However, addressing storm overflows is only one part of the picture when it comes to improving water quality. The Environment Bill requires the Government to set and achieve at least one new target to drive progress when it comes to water. In the policy paper published in August 2020, the Government set out the objectives for targets currently under consideration. For water, these include reducing pollution from agriculture, wastewater, and abandoned metal mines, and reducing water demand.

Funding for the Catchment Sensitive Farming programme has almost doubled with an additional £17m over the next three years. The new annual budget will be £30m, up from £16.6m in 2020 / 21. This includes allocating £1.2 million to the Environment Agency to significantly increase the number of inspectors visiting farmers to reduce diffuse water pollution, with 50 additional full-time employees recruited for inspections. Taking a catchment wide approach to water management is vital in our more holistic approach to water management.

Over 3,000 hectares of new woodlands are set to be planted along England’s rivers and watercourses. Planting trees on and around riverbanks, or allowing them to grow naturally, can help to improve water quality by reducing the runoff of pollutants into rivers.

The Environment Bill is landmark legislation that will clean up our rivers and seashore and make a massive environmental difference to my constituents in Poole and I am proud of my Government’s record in pursuing these objectives.

Sir Robert Syms MP

Member of Parliament for Poole

CEFAS Reports on Poole Harbour - a summary

In 2009 CEFAS published "CLASSIFICATION OF BIVALVE MOLLUSC PRODUCTION AREAS IN ENGLAND AND WALES - SANITARY SURVEY" and in 2016 the same department published "West Brownsea Island Relay Area Cockles and Tapes spp. Provisional RMP Assessment"

The former totals 38 pages long and the latter 19, and whilst they focus on bivalve health and saftey there is a lot of detail included that relates to the condition of the water in Poole Harbour so I have combed through both and extracted the salient points here.

2009 CEFAS Sanitary Survey of Poole Harbour

Page 3

"The continuous sewage effluent discharges to the harbour from the large sewage treatment works at Poole, Lytchett Minster and Wareham STW receive year-round UV disinfection. This will inevitably reduce the impact of these discharges on shellfisheries in the harbour. There are a number of smaller sewage treatment works effluent discharges and storm and emergency overflows to the harbour that may have localised impacts."

"The main freshwater inputs to the harbour are from the Rivers Frome and Piddle, with smaller inputs from the Corfe River, Sherford River and several other streams. These rivers are likely to be more significant sources of contamination than the sewage effluent discharges to the harbour."

"Analysis of recent microbiological data for the production area indicates that microbiological water quality in the harbour is generally good (typically class B), although high levels of contamination have been recorded in the Wareham Channel and Holes Bay. Seasonal variation in levels of contamination is evident at several sites (but not all), with the highest levels of contamination in the winter."

Page 6

"The estuary has a catchment area of around 800km2. Approximately 70% of the estuary catchment is farmed, with cereal, dairy and cattle and sheep farming being predominant (Environment Agency, 1999)."

Page 14

"..there is also a traditional fishery in the sandy littoral areas of the harbour such as Whitley Lake where cockles are harvested by hand rake (Royal Haskoning, 2004; Jensen et al., 2005a). The harvesting season for wild cockles extends from 1st May to 31 January"

All good so far but then we get on sewage discharge..

Page 15

This is consented flow of treated sewage (mostly UV) that runs continually as, bluntly - the stuff needs to go somewhere. But it shows the sheer volume of discharge into Holes Bay under normal conditions - frankly the remaining outlets even when considered together pale into insignificance.

"Faecal coliform concentrations in the effluent from Poole STW have increased since 2006. The underlying cause of this deterioration in effluent quality is not known." 

The report was released in 2009 remember but their figures back that comment up, showing a steady increase in the levels of post-disinfection faecal coliform data (RH Column)

Page 18

This is where it gets to storm water discharge:

"Intermittent sewage discharges (storm and emergency overflows) to shellfisheries represent a significant risk to human health (Garreis, 1994). Storm sewage is untreated sewage in a mixture with surface run off from combined sewerage systems that discharge via combined sewer overflows (CSOs) and/or storm sewer overflows (SSOs). Although some dilution from rainwater is afforded, the bacterial loading of storm discharges is significantly higher than treated sewage effluent (particularly where UV treatment is applied to the latter), with faecal coliform concentrations typically around 105-106 cfu per 100ml (Kay et al., 2000, Lee et al., 2003). Emergency discharges of untreated sewage occur in the event of a fault in the sewerage infrastructure (typically a blockage or pump failure)."

"The overflows from Sandbanks Pavilion sewage pumping station (SPS), Seacombe Road SPS, Elgin Road SPS and East Quay SPS are within or close to the cockle fishery in Whitley Lake in the north-east of the harbour and storm or emergency discharges from these assets are likely to have a significant impact on levels of microbiological contamination of shellfish in the vicinity of the discharge point. No microbiological monitoring is currently undertaken in this area."  (this article was in  2009 and there has been sampling of mussel flesh in Whitley Bay there since 4th June 2015)

Page 23

"ADAS (2003) developed a catchment level model (Catchment Source Apportionment Tool, CSAT) to calculate the faecal coliform load exported from the Frome and Piddle catchments to Poole Harbour. The model incorporated the loads from both point sources (STWs and CSOs) and diffuse organic wastes spread to agricultural land (both naturally from livestock and artificially applied as manure or slurry). The model calculated that point sources are responsible for more than 95% of the annual faecal coliform load exported from the catchment, with CSOs being the most significant source during storm events. Predicted faecal coliform concentrations at the tidal limit showed a seasonal pattern with concentrations peaking in the winter. This may partly account for the similar seasonal pattern in E. coli levels in shellfish seen at several sites in the harbour (See section 5)." (Emphasis mine)

Page 26


There are areas of grazing land bordering the south and west of Poole Harbour and several beef and dairy farms in close proximity to the shore. Discharges and run off of farm waste (slurry or manure) from these farms have the potential to contribute to levels of microbiological contamination in shellfisheries in these areas. However, the Environment Agency is not aware of any issues at these farms that suggest they are a significant source of contamination (Julian Wardlaw, Environment Agency, personal communication)." (Emphasis mine)

Page 27

"..the EA has undertaken monthly monitoring at three additional sites in order to assess the impact of UV disinfection at Poole, Wareham and Lytchett Minster STWs on water quality in the harbour. The locations of these sites are shown in Figure 5.1. A summary of faecal coliform data for the period 2003-2009 (post completion of the UV disinfection schemes) is given in Table 5.1.

"95% of samples must conform to a faecal coliform concentration of less than 2000cfu per 100ml and a total coliform concentration of less than 10,000cfu per 100ml in order for a site to pass the Imperative (I) standards of the Directive. 80% of samples must conform to a faecal coliform concentration of less than 100cfu per 100ml in order to meet Guideline (G) standards. In England and Wales, guideline compliance is also assessed against a national faecal streptococci standard of 100 per 100ml (as an 80 percentile)."

Poole Bridge is located at the outlet to Holes Bay - the maximum figure most likely reflects discharge of raw sewage during storm conditions and shows how bad things can get.

Page 28

"A summary of the E. coli data for the period 2004 to 2009 (post completion of the UV disinfection schemes) is given in Table 5.4. Sporadic results above 4,600 MPN per 100g have been recorded at all sites within the harbour. The highest levels of contamination have been recorded at Barrel ‘O’ and Rockley monitoring points in the Wareham Channel. Both sites have returned E. coli levels above 46,000 MPN per 100g (i.e. ‘Prohibited’ level results)."

Page 36

"Whilst existing monitoring points are generally well placed in relation to these sources, there is currently no monitoring point in the wild cockle beds in the Whitley Lake area."

In the summer at low tide you will see dozens of people (largely form the local Chinese community) collecting cockles from the sand in Whitely Lake

Page 40

"6. A new monitoring point at North Haven Yacht club (B54CN) should be introduced at Whitley Lake in order to classify the wild cockle beds in this zone. Monitoring at this site is recommended because of the potential for contamination from intermittent sewage discharges in this area. The monitored species should be cockles." (This was attempted but it transpired that cockles do not travel well so mussels were used instead; further studies showed that mussel meat is not a good proxy fro cockle meat when it comes to E. Coli saturation so a mixed result.)

CEFAS 2016 Provisional RMP Assessment

Page 4

Page 8

"At present, the majority of Poole Harbour is classified B-LT for a variety of species. One area (Wareham Channel) where the influence of the Rivers Piddle and Frome is the greatest is currently classified as C for the species harvested from there. The majority of these classifications (including all classifications for Tapes spp. and cockles) are based on the results of mussel samples taken from deployment bags. Whilst this may be a historically accepted practice in Poole Harbour, there is growing evidence from other areas (e.g. Langstone Harbour) that Tapes spp. accumulate E. coli to a much higher level compared to mussels (Lewis Coates, pers. comm). This has had major consequences for other shellfisheries in such areas (eg. native oyster sampling may return a B classification whereas sampling of Tapes spp. may return prohibited level results.) This implies that Tapes spp. should be sampled in preference to mussels, although it is understood that there may be
practical challenges in doing so."

"Since 2006, there were seven instances where both mussel and Tapes spp. were sampled from the same location on the same date. These individual results are listed in Table 4."

"The number of samples considered is limited but illustrative of the potential weaknesses of using mussels to classify Tapes spp. On all these occasions Tapes spp returned a higher result than mussels, and on three occasions results for Tapes spp exceeded 4600 E. coli MPN/100g when the results for mussels were below this threshold."

So - it isn't practical to sample cockles as they don't travel well, so mussels are used as a proxy. Fine but it appears that cockles accumulate E. coli at a faster rate. Given that the cockles in Whitley Lake are collected and eaten by the public this would seem to be something that is important to resolve.

Present Day

For a more up to date take, CEFAS' own website has a trove of data on shellfish pollution - as expected they are still sampling mussels not cockles but it is at least in Whitley Bay. They did sample off NHYC for a few months in 2016 before opting for a site in the centre of the area:

The results are interesting bearing in mind how mussels are shown to be an unreliable predictor for the safety of cockles (the vertical scale is logarithmic) with a maximum E. coli count of 2400 E.coli per 100g on August 6th 2019 and levels that are massively higher than those found off Barrel 'O' (located North of Brownsea Island).

Now bear in mind that when cockles and mussels are taken from the same area and tested, the cockles were found to have up to 28 times higher levels of E.coli than the mussels, it does suggest that the cockles should be tested separately, and that perhaps all is not well in Whitley Lake.

According to the interactive CEFAS map, cockles are tested in Portsmouth and Chichester Harbours but there is no testing of them whatsoever in Poole Harbour.

Public safety

E. coli dies when the cockles are cooked, so as long as that's done properly the levels are not a threat to the public, though reheating food with E coli present may be a problem, as the bacteria seems to gain super powers (emphasis mine):

"At the ARS Eastern Regional Research Center's Food Safety Research Unit in Wyndmoor, Pa, Vijay K. Juneja and colleagues heated beef gravy samples contaminated with E. coli 0157:H7 to 114.8 °F for 15 to 30 minutes. The heat was not sufficient to kill the bacteria, but enough to stimulate it so that it could adapt to the stressful heating conditions. They then cooked the gravy to a final internal temperature of 140 °F.

Pre-heated E. coli survived longer at the higher temperature—a 1.5-fold increase in heat resistance—than E. coli not subjected to sublethal temperatures. And, the increased heat tolerance lasted for at least 48 hours.

This research suggests to food processors that slowly heating foods to the final cooking temperatures normally used may not kill bacteria. Heat-shocking conditions may occur in refrigerated, cook-in-bag foods such as filled pasta, beef stew, roasts and soups. The slow heating rate and low heating temperatures widely used to prepare these foods may expose potential pathogens to heat shocking conditions, thereby making the microbes even more heat-resistant."


  • Everything is fine until it rains.
  • On a good day Poole STW discharges far and away the most sewage into the Harbour
    • dry weather flow of 47,700 metric tons per day compared to the second highest discharge at just 2502.
    • as we know, storm discharge volume is not monitored
  • Farm discharge is not the culprit

Is the level of E. coli in shellfish a good indicator of whether the water is safe to swim in? It's not clear-cut as different shellfish handle bacteria with varying degrees of success and each are continually trying to rid themselves of it, so levels will vary substantially over time. There is something to be said for the short term 'averaging' ability of the shellfish vs the sporadic water sampling that may miss recent spills but overall more research is needed.

Perhaps daily testing of mussels, cockles at the same location and the water around them throughout the year may yield a reliable model and enable the little guys to become cheap and robust sentinels of the Harbour's health.

Images and text from any government reports in this article are included subject to the Open Government Licence for Public Sector Information.