Dry weather and increased monitoring cuts CSO spills

There were 70,000 fewer spills from combined sewer overflows (CSOs) in 2022 compared to the prior year, Environment Agency (EA) statistics reveal.

As well as fewer spills, the duration of spills also reduced year-on-year

The data showed the average duration of each discharge fell to 5.8 hours in 2022, down from 7.4 hours the previous year.

The EA highlighted the progress companies made adding event duration monitors (EDMs) to CSOs being on track for full coverage by the end of this year, as required. Across England and Wales, 91% of CSOs were fitted with EDMs.

Monitoring began in 2016 when just 862 CSOs had a monitoring device fitted. By 2022, 13,080 of the 14,580 CSOs recorded spill data.

The average number of discharges per CSO was 23, which is down from 29.4 in 2021. Discharge numbers rose as more EDMs were fitted from 2016 onwards, peaking in 2019 at 35.4 spills by CSO. As the sector came under pressure to curb discharges and government set targets to reduce spills, the number has declined. Likewise the duration of all spills peaked in 2020 at more than three million hours and fell to 1.7 million hours in 2022.

However, EA executive director John Leyland said the improvement was “largely down to dry weather, not water company action”. He said: “We want to see quicker progress from water companies on reducing spills and acting on monitoring data.

“We expect them to be fully across the detail of their networks and to maintain and invest in them to the high standard that the public expect and the regulator demands.”

In total, 301,091 monitored spill events were recorded by 10 wastewater companies in England and Wales during 2022.

The EA data showed 3% of CSOs spilled more than 100 times in the year, which was down from 5% in 2021 while 18% did not spill at all.

Trade body Water UK described the decline in spills for a fourth consecutive year as “an important milestone”.

A spokesperson said: “This is the start of the journey and to ensure we continue to see these numbers move in a positive direction water companies are bringing forward £56 billion of investment to replumb England, fix storm overflows and protect our rivers and seas. There remains much more to be done, and there will be bumps in the road, but companies are committed to building on this positive news to ensure we play our role in bringing about the transformation we all want to see.”

Spill numbers varied by company as some regions have a higher proportion of combined sewer systems.  Welsh Water has the fewest CSOs (126) and its spill numbers correlate at 2,800. United Utilities recorded the most discharges at 69,000 from its 2,254 CSOs, reflecting the higher number of overflows in its region owing to the age of urban systems. UU drove spills down by more than one-third last year as it invested in river health across its region.

Good Law Project, the legal group supporting action against United Utilities over discharges in the Manchester Shipping Canal, said the data revealed a need for tighter restrictions around the operation of CSOs.

Its director, Jolyon Maugham, said: “The right answer is new laws to bring this shocking state of affairs to an end. The problem is the stranglehold that the corporate owners of these huge water companies have over Government policymaking. And the victim is the public, you and I, who live in a country that is, literally, overflowing with raw sewage.”

Nearly half (48%) of EDMs recorded fewer than 10 spills in the year across the sector. The government’s Storm Overflows Discharge Reduction plan published last summer stipulated all discharges should be below 10 per year by 2050.

Labour’s Liz Twist this week challenged water minister Rebecca Pow to be more ambitious on discharge reductions. In a Defra Q&A she said Labour intended to cut discharges by 90%, mandate sewage outlet discharges and automatically fine for discharges.

Pow, however, hit back and said the opposition’s plan would add £1,000 to customer bills as well as cause disruption from additional pipework required. She said government was doing “everything that was called for and more” to take tougher sanctions on pollution incidents while being mindful of bills.

Monitoring was introduced by the EA from 2015 when the Agency identified a problem. Data from EDMs sparked public and political outrage aimed at the water sector for damaging waterways. Monitoring does not provide a comprehensive picture of harm done by discharges from CSOs as spills into larger watercourses following heavy rainfall are less damaging than short spills into small or sensitive waters. The EA said monitoring will be enhanced in future but admitted its own underfunding left it without proper sight on the problem.