The Welsh Government has published a review of the costs and benefits of different storm overflow control policies for Wales. The analysis considers capex, opex, bill impact, benefits, net present value and carbon associated with both traditional infrastructure and “blue green” approaches.

The report finds that

• The capital costs of removing the harmful environmental impacts of storm overflows rather than reducing spill frequency would be £1.5-£2.7bn, adding £50-£90 to a Welsh Water bill.
• Reducing spills to no more than ten per year (in line with proposals in England) would result in capital costs of £2.5-£6.5bn, adding £80-£220 to a Welsh Water bill.
• Eliminating all spills due to rain would cost £7-11.9bn, with a Welsh Water bill impact of £215-£390.
• Blue green or hybrid approaches generally cost more but also result in much higher benefits. However, benefits never outweigh costs under any option.

These conclusions are similar to recent work for Defra in England to support the Storm Overflows Discharge Reduction Plan.

Minister for climate change Julie James said the Wales multi-stakeholder Better River Quality Taskforce will now consider carefully the report and identify next steps. She commented: “We need to strike a balance between taking effective action whilst keeping bills affordable, particularly given the current cost of living crisis.”