Many of our sewer systems are combined systems, where sewage is combined with rainwater. During and after heavy or prolonged rainfall, or if the groundwater table is high, the capacity of combined sewer systems can be exceeded. Storm overflows act as relief valves to discharge excess sewage combined with rainwater to rivers or the sea, protecting properties from flooding and preventing sewage backing up into streets and homes. Storm overflows are a last resort in modern sewer design, but the age of our sewerage systems means their complete elimination is not practicable or affordable. I am assured, however, that Ministers recognise there is more to do on the issue of sewage pollution and are very supportive of the aims of this Bill. I share your concerns about this matter, especially for local rivers such as the Stour.
My Ministerial colleague, Rebecca Pow MP, met water company CEOs in September 2020 and made clear that the volume of sewage discharged into rivers and other waterways in extreme weather must be reduced. I am aware that water companies are already committed to a significant programme of improvements to the monitoring and management of storm overflows at a cost of around £1.2 billion, including over 700 schemes to provide environmental improvements by reducing spills from frequently spilling overflows.
As well as this, through the Environment Bill, sewerage undertakers will be required to produce a statutory Drainage and Sewerage Management Plan to actively address environmental risks, such as sewer overflows and their impact on water quality. Ministers have also set up a new Taskforce to set out clear proposals to address the volumes of sewage discharged into our rivers.
Locally, I have been working with landowners and Wessex water to improve matters here in Mid Dorset. If you have specific concerns about a river or sewage discharge I would encourage you to raise it with the Environment Agency who can act in certain circumstances.