Combined Storm Overflow Statement

12 April 2021

As a not for profit company so closely linked to the environment, we are very aware of the impact our operations can have on our surroundings and take our environmental performance very seriously. This includes the operation and maintenance of our extensive wastewater network which includes more than 830 wastewater treatment works and over 37,000km of sewers.

Our network also includes combined storm overflows (CSOs) which play an essential role in stopping sewage from backing up into customers’ properties during periods of heavy rain.  They usually release storm waters into rivers or the sea and their operation is highly regulated and closely monitored by our regulator Natural Resources Wales.

Whilst CSOs are mainly operating as designed and permitted, we recognise that with environmental legislation tightening and customer expectations changing, more needs to be done. However, this requires significant additional funding and will take many years to deliver. 

We have invested £8.1 million in improving the monitoring of the CSOs since 2015, and now have spill monitors on 96.7% of all of our CSOs – more than any other water company. These monitors record the number and duration of spills and this data is published on our website allowing us to develop investment cases to make further improvements and also to provide real time spill information for key bathing waters to interested bodies, including Surfers Against Sewage.

As our profits don’t go to shareholders but instead are reinvested to improve our services, over the past 20 years we have invested over £1billion in our entire wastewater network.  We know however that there is still further work to be undertaken and that is why we are investing £765 million between now and 2025 on further improvements to our wastewater system.  This includes around £60 million programme agreed with NRW to tackle priority CSOs.