The Environment Agency does not hold the data for the volume of sewage released by storm overflows.
Working with water companies, the Environment Agency has concluded a programme to install Event Duration Monitors on the vast majority of storm overflows, just over 80% of the overflows in England by the end of 2020. These monitors provide a robust and consistent way of monitoring how often and for how long storm overflows are used, but do not measures volume. This underpins the Environment Agency planning, compliance and enforcement work. By the end of 2023, the remaining number will be monitored to provide a complete picture of permitted storm overflows in England.