Under the Environmental Information Regulations 2004 please provide me with the following.
The volume of wastewater that is discharged into the environment via storm overflows for each year from 2016 to 2022.
Acknowledged?Due DateData provided?InformationNotes
Anglian Water Y5/5/23NStorm overflows are only monitored for the number and duration of spills, and the volume is not measured.
Northumbrian WaterY8/5/23NNorthumbrian Water does not measure the volume of discharges at storm overflows therefore
this information cannot be provided. Reg. 5(1) only obliges a public authority to provide
environmental information which it holds. Your request therefore falls outside the Regulations.
Severn Trent Water8/5/23NOur Event Duration Monitors are designed to operate as per regulatory guidelines and do not monitor volumes, we are therefore unable to provide the information requested as this is not information we hold.
Southern WaterY5/5/23NWe can confirm that Southern Water does not hold information of the type you have requested as
Under the Regulations Southern Water does not have to provide you with a copy of this information
if one of the exceptions in the Regulations applies. In this case Southern Water considers that the
exception Regulation 12(4)(a) of the EIR applies as we do not hold the information you have
requested. Therefore, we are unable to provide you with this information
South West WaterY6/5/23NI can confirm that SWW does not hold the information you have requested. Storm overflows are
monitored by Event Duration Monitoring (EDM) equipment which only record start and stop times,
no volume information is recorded.
Thames WaterY5/5/23NThames Water does not record the volume of wastewater discharged into the environment via storm overflows therefore section 12(4)(a) of Environmental Information Regulations (EIR) applies where the public authority does not hold the records requested.
United UtilitiesY5/5/23NWe measure the frequency and duration of storm overflow operations using Event Duration Monitors (EDMs) and have reported to our regulators on this since 2020. The EDMs do not record volume and therefore we are unable to provide the information you have requested as we do not hold it.
Wessex WaterYNWe have event duration monitors installed on our storm overflows, which only record durations (time), so the information requested (volume) is not available.

It is worth noting that flowrates on their own would not add much value. What would need to also occur would require additional instruments that measure the concentration of certain parameters (such as ammonia, suspended solids, biochemical oxygen demand) within the discharge. The two pieces of information – flow and concentration, could then be used to calculate the organic load being discharged.

More importantly, putting in flowmeters would soon be superseded by the current plans to monitor river water quality upstream and downstream of every overflow as required by Section 82 of the Environment Act 2021. This monitoring will then show whether an overflow discharge is reducing the levels of dissolved oxygen or increasing the levels of ammonia in the waterbody below or above the environmental quality standards set.
Yorkshire Y6/5/23NWhilst we monitor our storm overflows the data we collect is predominantly level data at the spill weir. This gives us the ability to determine frequency and duration of spills but not volume. This means a spill from large sewage treatment works is recorded the same as a small network CSO.
Dwr Cymru / Welsh WaterY6/5/23NPlease note, the monitor doesn’t record the volume (measurement) of a spill event for us to hold data to disclose.