Poole Harbour Sewage Pollution Leaflet Response Oct 2021
Hello and thank you for responding to our leaflet.
We started looking into problems with the water quality in Poole Harbour in 2020 after Surfers Against Sewage (SAS) released their 2020 water quality report showing the outfall at Shore Road beach by Jazz Café, Sandbanks to have had the highest number of discharges in England and Wales, despite the water being rated 'Excellent' by the Environment Agency (EA).
That particular beach is on the seaward side and SAS' results are contested by Wessex Water, but in looking into the issue we found that Poole Harbour is severely overlooked by the Environment Agency on the water quality sampling front - this map from the EA’s website (annotation ours) shows that there are only two sampling points in the Harbour and both are upstream of Holes Bay where the vast majority of sewage outfalls are located.
Fig 1 – Freshwater inflow and sewage discharge on an outgoing tide
In normal conditions the sewage outfalls in Poole Harbour discharge treated sewage which is clean enough to allow the shellfish industry in the Harbour to operate (albeit degrading the product's classification) and for people to safely enjoy ocean sports. But in times of heavy rain the sewage treatment plants are overwhelmed and then a mixture of raw sewage and rainwater flows into Holes Bay and from there out into the Harbour where it slowly dissipates (Poole Harbour is only a few feet deep on average and does not flush as rapidly as a river). This is down to the way in which sewerage systems across the country were historically constructed as combined systems to take foul and surface water combined. Replacing the network with a system that handles rainfall separately would be a gargantuan task given the extent of it.
Wessex Water are permitted to do this within limits set by the Environment Agency but rather surprisingly the volume of discharge is not known as it is not monitored, so there is no way of knowing whether or how often limits are being exceeded.
It is worth noting here that if all sewage companies monitored volume of discharge then it would be possible to more accurately compare one company or one outfall to another, in which case there is a good chance Shore Road Beach would not have featured at the top of the SAS’ list of most polluted beaches.
That was our initial push - to find a way to monitor the amount of sewage being pumped or poured into the Harbour (the discharges at the end of July 2021 for example were sufficient to force the Harbour's shellfish industry to have to close down for 2 weeks). Wessex Water have shown us in detail how the sewage treatment process works and provided a great deal of discharge data that we have presented on our club site. We have had lengthy meetings and looked into wet wells and outfalls to investigate how viable laser or ultrasonic measurement might be used in calculating volume of discharge but the impact is determined by the dilution factor (how much rainwater vs. how much sewage), and developing standard measurement equipment is complicated by the wide range of buried infrastructure.
Whilst monitoring the volume of discharge may still be an option (most likely via a combination of modelling and measuring), and BCP Council are investigating the viability of using AI buoys to monitor the Harbour water quality (it's very early days there and a result isn't a given), we have decided to approach the problem from both ends and look into how to get the water itself sampled regularly.
Over the next year we are aiming to get Whitley Lake (inc. Kite Beach) designated as a Bathing Water so that it is sampled 20 times per bathing season (May to September) by the Environment Agency. CEFAS tidal flow maps in the article on our club site show that the efflux from Holes Bay heads straight to Whitley Lake and, given how massively ocean sports activity in the area has increased over the last few years we feel that it’s time for the classification system to reflect that and warn & protect the kiters, SUPs and swimmers etc. as well as local fisheries.
To do this we will need to take headcounts of people in the water over next summer and we are partnering with some of the ocean sports companies in the area to achieve that. By this time next year we should hopefully be able to submit a claim to DEFRA to have the area monitored from May 2023 onwards. ills.
Chances are that it won't go smoothly but it's a worthwhile objective to achieve for locals, tourists and the businesses that rely on the cleanliness of the Harbour. For now - if you are a beach-based business that can help with headcount May-Sept 2022 then please get in touch, otherwise please feel free to forward this email to friends who may be interested as I sense this may become a political issue, at which point local support will be vital.
And just don't swim after a storm!
BeachPeople is a private members club for adults who enjoy Ocean Sports & fitness.
To The Beach!
(Updated 6th October 2021 following feedback from Wessex Water)