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

To ask the Secretary of State for Environment, Food and Rural Affairs, how many litres of untreated sewage spilled into the River Derwent in Mid Derbyshire in (a) 2018, (b) 2019 and (c) 2020.

Event Duration Monitors (EDM) record the number of times there has been a discharge of storm sewage and for how long each discharge was for. The Water Companies send in an annual summary which gives the total number of discharges per year and the total duration per year for each site where it is a permit requirement. The 2020 data is not yet available as it is submitted at the end of February.

Event Duration Monitors started being installed in 2016 and have been progressively installed across Combined Sewer Overflows, Sewage Pumping Stations and Sewage Treatment Works. Not all sites require EDM monitoring, this depends on the sensitivity of where the discharge is made.

Direct storm sewage discharges to the River Derwent, Derbyshire (Source to confluence with River Trent)

The discharge from these water company assets (in this case Severn Trent Water Ltd) is only permitted to occur when there is elevated flow in the combined (sewage and surface water) sewerage network due to rainfall/snowmelt. The discharge is known as storm sewage and the impact on water quality is reduced due to the increased dilution both within the sewer and the receiving watercourse.

In January 2021 the Storm Overflows Taskforce announced plans by the water companies to accelerate work to install monitoring devices on all storm overflows by 2023. The Environment Agency is working with all water companies to increase the transparency of EDM data by 2022. This will provide readily accessible data in a consistent format, which will give greater visibility and increase responsibility of water companies to go faster and further in reducing harm from storm overflow discharges.