Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, what steps the Environment Agency is taking in relation to Thames Water following reportedly unmonitored sewage spills into the Thames from the Mogden sewage treatment works.

The Environment Agency (EA) has confirmed that there have not been any unmonitored discharges into the River Thames from Mogden Sewage Treatment Works (STW).

The EA monitors all discharges to the River Thames from Mogden STW.

Storm sewage discharges occur when sewers or sewage works are overwhelmed by the extra water from rainfall. These outfalls are permitted by the EA and act as relief valves to prevent sewage backing up and flooding property and roads. The EA has powers to investigate non-compliance with permit conditions at Mogden STW and take appropriate action should non-compliance be established

As a regulatory requirement, Event Duration Monitoring (EDM) has been installed on Water Company storm overflows over the last five years. This has been part of the Asset Management Planning process agreed between the Water Services Regulation Authority (Ofwat), the EA and the Water Companies. Further monitoring is planned for the period 2020 to 2025 with more than a 1,000 monitoring installations across the country.

The program of installation was completed in March 2020 and since then the EA has accurate and complete EDM data sets. The data has been published and it has been acknowledged that data sets prior to March 2020 were sometimes incomplete as monitoring equipment was commissioned and data handling and reporting protocols were implemented.

However, protocols in place before and during the installation of the EDM ensured that the EA and the public received notification of all storm discharges from Mogden STW through storm sewage discharge notifications. The notifications include details of times and volumes, and the EA were able to use the data to monitor the site’s discharges within the requirements of their permit.

Although it is not a regulatory requirement, this storm discharge data is made publicly available by Thames Water. The EA continues to receive and assess the data from Mogden STW when it discharges to the river.

A new Storm Overflows Taskforce has been established comprising of Defra, the EA, Ofwat, the Consumer Council for Water, Water UK and Blueprint for Water. The Taskforce is meeting regularly to set out clear proposals to reduce the frequency and volume of storm sewage discharges into waterways in extreme weather. The Taskforce is also exploring further short term actions water companies can take to accelerate progress in reducing storm sewage discharges.