Unusually heavy or prolonged rainfall can result in excess water flowing into our combined sewers which causes them to exceed their capacity. 

When this happens, we need to protect properties from flooding by using combined sewer overflows (CSOs) which prevent sewage backing up and overflowing into the streets. 

CSOs acts as a relief valve within our system, enabling us to release the excess storm water into a river or the sea. 

We have identified 13 areas where this is happening frequently and have committed to making improvements within the next five year AMP period. 

Measuring our performance against this commitment will help us to improve the environment