Groundwater infiltration reporting rules introduced by the Environment Agency are increasing pressure on water companies to quantify and reduce inflow and infiltration (I&I) across wastewater networks.
Ryan Pearson, Head of Strategy at Metasphere, commenting on groundwater infiltration regulation.
New guidance, Discharges from groundwater surcharged sewers (RPS 362), sets out how unpermitted discharges caused by groundwater infiltration will be regulated during AMP8. The rules require utilities to evidence infiltration reduction planning, monitoring and long-term remediation within their Drainage & Wastewater Management Plans (DWMPs).
Groundwater infiltration reporting rules reshape AMP8 compliance
The guidance is effective immediately and runs until 31 March 2030. Key requirements include:
- Infiltration Reduction Plans (IRPs) to be included in draft DWMPs by November 2027
- Revisions to be submitted within one month if rejected by the Environment Agency
- All measures finalised by August 2028 and included in final DWMPs
- Post-2030 enforcement under standard sanctions policy
The Environment Agency has indicated that enforcement action will not be taken where strict reporting and remediation conditions are met before 2030.
Ryan Pearson, Head of Strategy at Metasphere, a Grundfos company, said utilities must move beyond traditional modelling approaches and adopt higher resolution flow monitoring to isolate infiltration signatures.
High-fidelity data to quantify inflow and infiltration
Inflow and infiltration of groundwater into sewers increases hydraulic loading, reduces treatment headroom and contributes to storm overflows. Capturing precise low-flow and peak-flow data across networks is increasingly seen as essential to demonstrate regulatory compliance and optimise investment decisions.
Utilities are under scrutiny to evidence that infiltration reduction delivers measurable benefits, including increased sewer capacity, improved treatment performance and reduced spill frequency.
Case studies such as Severn Trent Water’s Mansfield Sustainable Flood Resilience project illustrate how detailed water level monitoring within sustainable drainage systems (SuDS) can support hydrological modelling and quantify storage performance. The scheme, due for completion in 2027, is expected to provide capacity to store more than 58 million litres of surface water.
Regulators and operators are increasingly seeking granular operational data to differentiate between rainfall-derived inflow and groundwater infiltration, enabling more targeted remediation and nature-based interventions.
For further coverage on groundwater, wastewater regulation and AMP8 planning, visit our Wastewater section.
