Utility Week

20 | MAY 2022 | UTILITY WEEK Water Analysis Coming clean on CSOs The Environment Act requires a 'progressive reduction' in the number of sewer overflows into rivers, but it is only now becoming clearer what this catch-all phrase might actually mean. D uring the passage of many bills through Parliament, the debates in both chambers can be heated and rancourous. But few have proved as head- line-grabbing as when MPs and Lords argued over the specific commitments to limit harm from Combined Sewer Overflows (CSOs) con- tained in what became the Environment Act when it was passed into law in November. Most people involved in the water sector or with an understanding of the role CSOs play in wastewater management would rec- ognise the implications of what reducing sewage discharges would mean for water companies and, ultimately, for bills. But how the phrasing in the Act was to be interpreted was not laid out until this month. The con- tentious "progressive reduction" has now been spelled out by the Department of Envi- ronment, Food and Rural Affairs (Defra) with a demand to lower total spills from CSOs by 80% by 2050, beginning with those that affect protected sites. The scale of the challenge was high- lighted by the publication of Event Duration Monitoring (EDM) data collected by the Envi- ronment Agency showing that in 2021 there were 372,533 permitted spills from CSOs aver- aging seven hours per overflow event. There are 14,470 overflows in England and Wales and the sector has been told to add monitors to all of them by the end of 2023. Some companies, such as Thames, already boast 100% coverage. Environment secretary George Eustice set time-bound expectations for wastewater companies to eliminate the impacts of 3,000 storm overflows by 2035 as part of the Storm Overflows Discharge Reduction Plan. He said: "We are setting specific targets to ensure that those storm overflows are used only in exceptional circumstances – deliver- ing on our Environment Act and building on wider work on water quality." The water sector laid out £3.1 billion of investment during the current Asset Man- agement Period to 2025 to improve sewer networks and minimise harm to the water environment. A further £144 million invest- ment was triggered by the Storm Overflows Taskforce work. The public outcry about CSOs has grown in recent years in response to Environment Agency reports of stagnating improvements to river water quality, as well as harm to biodiversity. Eustice's plan distinguishes between reducing the total number of discharges and cutting down the harmful impacts of CSOs at a number of protected sites. It proposes 70% fewer discharges into bathing waters during the swimming season by 2035, as well as a 75% reduction in the environmental impact of 3,000 CSOs. By 2040 it targets eliminating approxi- mately 160,000 discharges, which will be 40% of the total; and by 2050 further cutting this to eliminate 320,000 discharges – 80% of the total. Achieving such reductions will take a combined effort by the sector, its regulators and government as well as billpayer sup- port. Separating sewerage and rainwater systems to eliminate the use of overflows has been estimated to cost between £350 bil- lion and £600 billion and require substantial disruption. Water UK said: "If implemented, these historic proposals represent the single big- gest investment in the water environment since the 1990s. This level of transformation will require significant new investment over the next decade, building on the £3.1 billion of spending between now and 2025. "Crucially, meeting the targets will also rely on government taking action: first, to reduce the many years of regulatory approv- als needed to improve some overflows; second, to close loopholes like housing developers' right to overload sewers; and finally, action on flushed wet wipes that cause spill-triggering fatbergs." Reducing discharges at inland waters with other options such as more storage tanks for times of heavy rainfall would cost between £160 billion and £240 billion, which would impact water bills. Monitoring for transparency Within the Environment Act is a requirement proposed by Philip Dunne MP in his Private Members' Bill in 2021 to monitor CSOs and publish data on all discharges. Dunne, who also chairs the Environmen- tal Audit Committee that earlier this year published its damning report into the health of rivers, said the proposed targets would add greater accountability and responsibility to water companies to clean up their act. "We are under no illusion that the scale of the challenge is significant," Dunne says, EDM Annual Returns - Long-term Trends 2016 2017 2018 2019 2020 2021* Total number of overflows listed - - - - - 14,470 Total number of storm overflows with EDM commissioned - - - - - 12,707 Total number of storm overflows with spill data 862 2,515 6,182 8,276 12,092 12,393 Total number of monitored spill events 12,637 33,159 146,930 292,864 403,375 372,533 Total duration (hrs) of monitored spill events 100,533 170,269 898,784 2,489,167 3,101,150 2,667,452 Average number of spill events per overflow with spill data 14.7 13.2 23.8 35.4 32.6 29.4 Average duration (hrs) of each spill event per overflow 8.0 5.1 6.1 8.5 8.1 7.4 * In 2021 all storm overflows operated by the WaSC were requested, regardless of whether EDM was currently installed. Extra information was also collected in 2021; including status of EDM installation, reasons for any low % EDM operation or any high spill counts. Source: Environment Agency

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