The OEP is investigating the Department for Infrastructure (DfI), the Department of Agriculture, Environment and Rural Affairs (DAERA) and the Utility Regulator over the regulation of sewage discharges into Belfast Lough, it announced today (November 25, 2025).
The investigation will determine whether these authorities have failed to comply with environmental law in their respective duties of regulating how untreated wastewater, that includes raw sewage, is discharged into Belfast Lough and its surrounding rivers.
Natalie Prosser, OEP Chief Executive Officer (CEO), said: “Water is such a precious resource. The quality of our water is one of the most pressing environmental challenges we face.
“Nature is under unsustainable pressure in Northern Ireland, and one of the biggest issues is how wastewater is managed.”
She added: “We’ll be looking at whether the Utility Regulator and DfI have met their duties to take necessary enforcement action, where Northern Ireland (NI) Water may not be fulfilling their own responsibilities for sewage discharges. For DAERA, we’ll examine whether it has set and updated the conditions that allow sewage overflows to spill in line with legal standards.”
The investigation will examine the regulation of discharges of untreated sewage from Wastewater Treatment Works (WWTW) and Combined Sewer Overflows (CSOs).
WWTW are facilities designed to treat wastewater to make it safe to be returned to the environment. CSOs act as safety values, discharging untreated wastewater, that includes raw sewage, into rivers, lakes or coastal waters to prevent flooding. They are used when the sewer system’s capacity is exceeded during heavy rainfall and there is a risk of sewage backing up into homes, streets and businesses.
Ms Prosser added: “Our focus is on DfI, DAERA and the Utility Regulator because they are the primary regulators and play key roles in enforcing NI Water’s own responsibilities in relation to sewage discharges.
“NI Water is not in scope of this investigation as the OEP’s role is not to step into the shoes of the regulators, but to ensure that they themselves are fulfilling their legal duties.
“However, we will be speaking to NI Water and requesting information to support this work.”
She added: “Although our investigation will focus on Belfast Lough, we know similar wastewater and sewage issues exist at other rivers and lakes. Our interest is in driving improvement across the wider regulatory system. What we find in this investigation will be relevant across Northern Ireland.”
If the OEP finds failures to comply with the law, the aim of the investigation will be to improve compliance and regulation across the wastewater system leading to long-term water quality improvement.
The OEP action follows on from its report into the causes of Northern Ireland’s nature loss last year (2024). It confirmed that agriculture and wastewater are the two largest contributors to water pollution, due to excess nutrients from fertilisers, animal waste (coming from imported animal feeds) and sewage. Excess nutrients is a major cause of the blue green algal blooms that have blighted Lough Neagh in recent years.
Ms Prosser added: “We have been clear that nutrient pollution from both, agricultural and wastewater sources, need to be tackled to better protect and improve the water in lakes and rivers.
“This is a complex problem with no quick fixes, but our investigation will contribute to the work already underway in this area, so government and other decisionmakers can be targeted and effective in driving much-needed improvements in water quality.”
If failures to comply with environmental law are found the OEP will look to resolve these by working constructively with the authorities involved to achieve a positive outcome. If no agreement can be found the OEP can take court action.
This investigation has been initiated by the OEP. It is the OEP’s fourth investigation in Northern Ireland.
Notes
The investigation is a Statutory Investigation under paragraph 7, Schedule 3 Environment Act 2021.
Under this provision the OEP has powers to carry out an Investigation into whether a public authority has complied with environmental law. Public bodies have a statutory duty to cooperate with the OEP and provide it with such reasonably assistance as it requests. An investigation may lead to enforcement action by OEP.
For DAERA, the OEP will be investigating compliance with the Water (Northern Ireland) Order 1999 and the Urban Waste Water Treatment Regulations (Northern Ireland) 2007.
For DfI, the OEP will be investigating compliance with the Water and Sewerage Services (Northern Ireland) Order 2006 and the Urban Waste Water Treatment Regulations (Northern Ireland) 2007.
For the Utility Regulator, the OEP will be investigating compliance with the Water and Sewerage Services (Northern Ireland) Order 2006 as supplemented by the Urban Waste Water Treatment Regulations (Northern Ireland) 2007.
