Church Street Darton CSO kicks off £250m storm overflow improvement plan for South Yorkshire

Yorkshire Water starts work on £5.3m investment at Church Street combined sewer overflow (CSO), Darton on Monday 22 September to stop storm overflows discharging into the river Dearne. It’s the first of 92 storm discharge reduction projects across South Yorkshire over the next five years.

The programme immediately follows a £180m investment over the past two years, which has helped to reduce storm overflows discharging into watercourses by 12% in 2024, compared to 2023. 

Tom Broderick, senior project manager, Yorkshire Water, said: “We made great strides in reducing the number of storm overflow incidences in the last year.  But we know there is more to do, and we are working hard to make sure that we tackle storm overflows operating more often than we and our customers would like. 

“This marks the first of 92 projects across South Yorkshire to bring down the number discharges over the next five years.  It’s part of our largest ever environmental investment and we are really pleased to start this huge phase of work here in Darton, Barnsley.”

Contract partners, Ward & Burke, will start work to create a new underground storm tank to hold excess wastewater and reduce storm overflows discharging into the river Dearne during periods of prologued and excessive rainfall.

The new storage tank will hold up to a capacity of 190m3 of water - the equivalent of 1,266 bathtubs – holding this excess wastewater will reduce the number of overflows discharging into the river and help to improve water quality of the Dearne.  Flows are sent for treatment once capacity in the network has returned to normal levels.

Wayne Cocksedge, project manager, Yorkshire Water, said: “The upgrade at Church Steet Darton, is the first of a £95m investment package to upgrade 28 Combined Sewer Overflows (CSO) across Barnsley - one of nearly five hundred separate schemes - to improve storage capacity across Yorkshire over the next five years.

“We’re kicking off at Church Street, Darton and will keep impact and disruption to a minimum, with further CSO improvement schemes lined up for Worsborough, Darfield and Stairfoot.  The upgrade At Darton Church Street should be completed by May 2026.

Storm overflows are designed to act as a relief for the combined sewer network, which carries both wastewater and surface water, during periods of heavy or prolonged rainfall. They discharge when the system is at capacity to prevent flows backing up and flooding homes and gardens. 

Across Yorkshire, the need for storm overflows to operate will be reduced by building new: 

• Surface water sewers, to separate surface water and wastewater so that wastewater networks aren’t impacted by bad weather
• Underground storage tanks, to build additional capacity into the network
• Nature-based solutions, to build additional capacity into the network
• Sustainable drainage systems, to slow the flow of surface water into the combined network 

The storm overflow project is part of Yorkshire Water’s £8.3bn investment into its services and the environment over the next five years.