Water UK, the organisation which represents all the UK water companies, has said the water sector acknowledges the urgent need to tackle storm overflows – but more action is required from Government to accelerate progress.

Responding to the highly critical Water Quality Report 2022 published yesterday by environmental organisation Surfers Against Sewage, Water UK said:

“The sector acknowledges there is an urgent need to tackle storm overflows. They are set to launch one of the country’s largest ever infrastructure programmes, which, if approved by regulators, will deliver £56 billion of improvements for our rivers and seas. That builds on at least £3 billion of improvements in the last couple of years alone.

“To accelerate progress further, we need Government to end housing developers’ uncontrolled connections to sewers without first knowing their capacity, and to end the flushing of wet wipes made from materials that cause blockages and fatbergs.

“Both are major causes of sewer overloading and spills. We also need Government to implement existing legislation in order to increase the use of sustainable drainage systems (SuDS) on new developments as a means of reducing the volume of rainwater entering the sewer system.”

Dry spills are not automatically illegal - permit compliance determines illegality

Water UK also responded to analysis in the report by SAS based on Met Office rainfall data to investigate potentially illegal ‘dry spills’ where a sewage overflow has discharged when there has been no rain, suggesting it can indicate illegal activity.

The industry body explained that the likelihood of spills occurring in dry weather can be increased by a number of factors, including:

• Groundwater infiltration – pressurised ground water can squeeze its way into pipes (both public and private) and overwhelm the network and require overflows to prevent flooding of the catchments. Surface water ingress caused by tree roots and land movements damaging or fracturing pipes.
• Misconnected private surface water drains placing extra surface water volumes into the networks
• By sewer blockages, caused by improperly disposed wet wipes, fats, oils and grease. These factors simultaneously reduce the capacity of the sewer network, while adding unforeseen, hard to detect, and unpermitted surface water pressures on the drainage system.
• Drainage time – the size and complexity of the area drained by the sewer and the network itself means some areas take days to drain down after rainfall.
• A failure or an emergency situation – a failure of a pump or a power failure could result in a release event.

Water UK goes on to point out that on the permitting issue specifically, dry spills are not automatically illegal and that permit compliance determines illegality. Water companies operate under permits issued by the Environment Agency, Water UK said, which outline what is classified as a consented and unconsented release.

The permits take into account where a release can be made, the dilution factor, tides, sensitivity as well as the specifics of the receiving watercourse. Typically, permits state how much stormwater water companies have to retain in a storm tank together with how much flow they must pump through the treatment process before they can release it.