OEP identifies possible failures to comply with environmental law in relation to regulatory oversight of untreated sewage discharges 

The Office for Environmental Protection (OEP) has identified possible failures to comply with environmental law by the Department for Environment, Food and Rural Affairs (Defra), the Environment Agency and Ofwat in relation to the regulation of combined sewer overflows (CSOs).  

The OEP launched an investigation into the regulation of CSOs by the three public authorities in June last year after receiving a complaint alleging failures to comply with legal duties relating to the monitoring and enforcement of water companies’ management of sewage. 

CSOs have an important role to play in the system as they prevent sewage backing up into people’s homes when the sewage network is overloaded. But discharges from these overflows harm the freshwater, coastal and marine environments, and can also have adverse impacts for people who use them. Therefore, discharges should only occur in exceptional circumstances. 

The aims of the OEP investigation are to clarify the roles and responsibilities of the public authorities and to determine whether they have failed to comply with their respective duties. If there have been failures, the OEP will seek to improve regulation in order to achieve long term improvement in water quality. 

Currently, as a result of information gathered during the investigation, the OEP believes that there may have been failures to comply with environmental laws by all three of the public authorities. The OEP has issued Information Notices to each of them setting out the details of those possible failures. 

The public authorities have two months to respond to the Information Notices. The responses will allow them to set out whether they agree with the OEP’s view, and whether they agree or not, set out any proposed remedial action or practical measures to address issues. 

Helen Venn, the OEP’s Chief Regulatory Officer, said: “Improving the quality of water in our rivers and seas is a complex challenge. There are no quick fixes. 

“We recognise that a great deal is already being done to tackle the issue of untreated sewage discharges, and we welcome the intent of Government measures such as the  Plan for Water and storm overflow targets, as well as commitments to increase investment. We are aware that both the Environment Agency and Ofwat have investigations underway. We await the outcomes with interest. 

“We want to make sure that all of these measures and any investments made are as effective as they can be. A regulatory system that works as the law intends will be a key contributor to this. 

“As a result of our investigations so far, we think there may have been misinterpretations of some key points of law. The core of the issue is that where we interpret the law to mean that untreated sewage discharges should generally be allowed only in exceptional circumstances, such as during unusually heavy rainfall, it appears that the public authorities may have interpreted the law differently, permitting such discharges to occur more often.  

“This then has consequences for the regulatory activity that follows. The guidance provided by Government to regulators, and the permitting regime they put in place for the water companies, possibly allow untreated sewage discharges to occur more regularly than intended by the law without risk of sanction. This is what has created the possible failures to comply that we have identified. 

“Clarifying this point will ensure future efforts to improve water quality are built on a solid foundation. We will consider the responses from all three public authorities in detail before deciding next steps.” 

For the Environment Agency, the potential failures relate to the requirements of urban waste water legislation and the Agency’s resulting role in devising guidance, setting permit conditions for CSOs, and reviewing and enforcing of such conditions (1).  

For Ofwat, the potential failures relate to its interpretation of sewerage undertakers’ duties to effectually deal with sewage and Ofwat’s duty to make enforcement orders where sewerage undertakers fail to comply with such duties (2)

For Defra, the potential failures relate to the requirements of urban waste water legislation, water quality legislation, and Defra's duty to make enforcement orders where sewerage companies fail to comply with their own duties to effectually deal with sewage (3) 



1: The Urban Waste Water Treatment (England and Wales) Regulations 1994 which implement the Urban Waste Water Treatment Directive 1991 (91/271/EEC) and the Water Environment (Water Framework Directive) (England and Wales) Regulations 2017.  

 2: ss.18 and 94 of the Water Industry Act 1991.  

 3: ss.18 and 94 of the Water Industry Act 1991, the Urban Waste Water Treatment Regulations 1994 which implement the Urban Waste Water Treatment Directive 1991 ((91/271/EEC) and the Water Environment (Water Framework Directive) (England and Wales) Regulations 2017. 

OEP enforcement policy

Under section 41 Environment Act 2021 the OEP must publish a statement where it gives an information notice. This public notice is given pursuant to section 41 of the Environment Act 2021.  

Under section 35 Environment Act 2021, the OEP may give an information notice to a public authority if  

  • the OEP has reasonable grounds for suspecting that the authority has failed to comply with environmental law, and  
  • it considers that the failure, if it occurred, would be serious 

An information notice must include the following information:  

  • a description of the alleged failure(s) of the public to comply with environmental law  
  • an explanation of why the OEP considers that the alleged failure(s), if it occurred, would be serious, and  
  • a request for specific information relating to the allegation(s). 

A public authority must respond in writing to an Information Notice within two months by setting out its response to the allegation(s), and what steps, if any, it intends to take in relation to them. It also presents an opportunity for dialogue to seek to reach agreement with the public authority. If the response changes the OEP’s view on whether there has been a failure to comply with the law, or sets out steps the public authority intends to take to rectify the failure, then the OEP may decide not to take any further action in relation to the alleged failure(s).  

The OEP may choose to end its investigation and publish a report on its findings, or to continue with enforcement activity. If it is to continue enforcement, the next stage in the process would be to issue a Decision Notice. This is a formal document setting out its findings on the public authority’s failure to comply with environmental law, why this is serious and the steps the OEP considers it should take to put matters right. Public authorities must respond in writing and confirm whether they are going to take the steps required. 

Where court action is required to secure an appropriate outcome, in England, the OEP may commence proceedings in the High Court via an environmental review enabling the court to determine the matter in law. If, on an environmental review, the court agrees that a public authority has failed to comply with environmental law, it will publish a statement of non-compliance (SONC). Subject to certain conditions specified in the Environment Act, the court may also grant any remedy available via a judicial review. A public authority must publish a response to a SONC within two months of the conclusion of the proceedings including any appeal. That response must set out the steps it intends to take in light of the SONC. The public authority’s response is expected to present a meaningful and substantive approach to tackling the findings. 

Following all investigations (except those where the matter goes to court) the OEP must prepare a report which will usually be published. These reports will set out its conclusions on whether a public authority has failed to comply with environmental law.  

 Combined Sewer Overflows  

CSOs are a feature of most sewerage systems where surface water (e.g. rainwater from roofs, driveways, and roads) and foul flows (e.g. sewage and other effluent) are combined in a single pipe, and they do have an important and necessary function. 

They are designed to operate in response to rainfall and other acute precipitation and runoff events where the combined sewer reaches its capacity, and a release is needed to prevent the capacity of wastewater treatment works being overwhelmed, or else sewage backing up and flooding properties.   

The OEP has focused on ‘network CSOs’ which are overflows on the sewerage network rather than those found at sewage treatment works. The OEP excluded CSOs at sewage treatment works and inlets from its investigation. There are two main reasons for this. Firstly, there is a live investigation by Ofwat and the EA into potential failures of water companies to have sufficient storage or treatment capacities at sewage treatment works, as required by their environmental permits. Secondly, the treatment of sewage before discharge is absent from CSOs on the network. This removes an additional area of complication, helping to keep the investigation streamlined and manageable. Any conclusions from network CSOs will be considered to see if they could have applications that could be relevant to other types of CSOs. 

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