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.