The Environment Agency has published guidance on unpermitted discharges by water and sewerage companies (WaSCs) to prevent sewer flooding and surcharging from groundwater infiltration into sewers.

The guidance, in the form of a regulatory position statement (RPS 362) does not change the legal requirement to have an environmental permit where one is required.

The purpose of the RPS is to:

• minimise the negative impacts of groundwater infiltration on the sewer network
• ensure that WaSCs take the steps needed to reduce this infiltration
• ensure that sewers inundated with groundwater are designed, constructed and maintained in line with the requirements of the Urban Waste Water Treatment Regulations (UWWTR)

The RPS applies to groundwater infiltration inundated sewers only and covers how the Agency regulates unpermitted discharges to relieve pressures on these sewers during the AMP8 period 2025 to 2030.

The RPS does not apply to discharges that are predicted or found to be a category 1 or 2 incident as outlined in the Common Incident Classification Scheme (CICS) - such discharges will need appropriate action to prevent significant pollution.

For sewerage systems that are vulnerable to groundwater infiltration and may require over-pumping of discharges to relieve pressure on sewers, WASCs must meet specified conditions, including:

• Notify the Environment Agency and report any unpermitted discharges from sewers to the Environment Agency incident hotline by calling 0800 80 70 60.
• Notify the Environment Agency as soon as possible before any unpermitted discharge, or within 24 hours afterwards if the requirement is urgent
• Reference an existing or updated Infiltration Reduction Plan (IRP)
• Not over-pump from groundwater inundated sewers to the environment without first notifying the Environment Agency.

The EA also requires WASCs to present to the appropriate Environment Agency regulatory manager the infiltration reduction measures needed to address the need for over-pumping as a result of groundwater inundated sewers in an IRP and subsequently in a Drainage and Wastewater Management Plan (DWMP) to be published in draft by November 2027 and in final form by August 2028

These must include a detailed description and quantification of the pressures and consequences (if no action is taken) of groundwater infiltration in the catchment, including:

• details of infiltration (for example sewer flooding, a history of previous over-pumping, excessive downstream combined sewer overflow discharges, or inability to effectually drain in line with Section 94 of the Water Industry Act 1991)
• locations of infiltration
• details of likely impacts

They must also include:

• a detailed description of plans and timescales (including specific milestones) to investigate and resolve the source and severity of infiltration problems – this should address current and potential future issues of infiltration
• an assessment of the need for further expected unavoidable discharges from groundwater infiltration, indicating their location and the circumstances when they will be needed while infiltration reduction work progresses
• details of the proposed discharges including any monitoring and mitigation – such as treatment or screening of the discharges that will be in place and the maximum discharge rates
• presentation of AMP8 actions to address infiltration issues before 31 March 2030, when RPS 362 will be withdrawn – including the measures to be set out in the statutory DWMPs to continue to resolve or minimise infiltration and any further discharges from 1 April 2030.

PRS 362 also specifies that before making any unpermitted discharges to the environment as a result of the impacts of groundwater inundation in the sewerage system, WASCs must:

• take all reasonable steps to prevent unpermitted discharges from groundwater infiltration into their own (and others) sewers and drains
• only make an unpermitted discharge if there are no reasonable alternatives (I.e. discharges are unavoidable)
• if discharges cannot be prevented, take all reasonable steps to minimise the volume and duration of discharges to meet requirements under the UWWTR
• use other mitigation measures such as treatment or screening, or both, to reduce the impact of discharges in line with BTKNEEC
• inform other relevant stakeholders (such as customers, local authorities or environmental non-government organisations – eNGOs) of the actions you are taking and will continue to take through appropriate forums

After RPS 362 expires at the end of the AMP8 period on 31 March 2030, the WASCs must transfer infiltration reduction measures, including those in IRPs, to the relevant DWMP.

The Environment Agency will review the RPS before 2027, subject to any new legislation or government direction. WASCs will need to check back from time to time, including at and before the expiry date, to see if the RPS still applies, the Agency says.

Click here to access the guidance in full online