Tackling water I&I with 'hifi' data

Inflow and infiltration (I&I) of groundwater into the UK wastewater network presents a significant challenge for UK water companies as they seek to reduce overflows into receiving waterbodies, optimise treatment capacity and meet net zero carbon targets. The public attention on river pollution has rendered many of the traditional approaches to water management unacceptable, leaving water operators with a significant investment challenge for their asset management plans up to 2035.

While concrete storage tanks have been the default for managing excess flow, the Environment Agency (EA)’s new guidance: Discharges from groundwater surcharged sewers: RPS 362, specifies how unpermitted discharges caused by groundwater infiltration will be regulated during AMP8.

For water companies in England and Wales, the primary takeaway is that there will not be enforcement action, provided strict conditions regarding reporting and long-term remediation are met.

The key compliance details are as follows:

• The EA guidance is valid now, and expires on 31 March 2030
• All infiltration reduction plans (IRPs), and measures must be included in draft Drainage & Wastewater Management Plans (DWMPs) by November 2027
• If the IRP or infiltration reduction measures in the DWMP are rejected, then an updated IRP or infiltration reduction measures must be submitted within one month of notification by the EA
• All measures must be finalised by August 2028 and included in final DWMPs
• After 31 March 2030, the EA intends to treat all such unpermitted discharges in line with their standard enforcement and sanctions policy.

High quality data

With regulators now expecting a higher level of evidence, high-fidelity data is the only way to meet these new compliance standards, while also fulfilling the industry’s commitment to low-carbon, grey-green hybrid infrastructure. 

The approach needs to be that what gets measured, gets done. For too long the industry has lacked the verifiable data needed to identify and quantify groundwater infiltration load, to meaningfully measure its impact. With the EA’s new guidance on groundwater infiltration, this evidence base must be timely, accurate and effectively deployed.

Public attention on river pollution has rendered many of the traditional approaches to water management unacceptable, leaving water operators with a significant investment challenge

Reliable data is the rocket fuel that will allow utilities to prove the benefit of groundwater reduction initiatives across catchments, including improved treatment performance, increased sewer capacity and spill reduction. Additionally, this data can provide the evidence base need to enable nature-based solutions and meaningfully tackle I&I in a swift, environmentally sensitive, and cost-efficient way.

Beyond peak inflow, precise flow measurement across the entire operational network is vital. While extreme flow events are critical for safety assessments, capturing subtle low-flow data is also essential for validating hydrological and hydraulic models. This level of granularity ensures a holistic understanding of system performance and infiltration behaviour under all environmental conditions.

Traditional methods of collecting the required data to develop solutions are time consuming and expensive, while frequently lacking the required granularity to ensure investment brings the benefit expected.

Metasphere has set out to resolve this, bringing together multiple existing datasets across wastewater systems into a single platform. Layering this information with automated calculation workflows makes it possible to demystify network characteristics during rainfall events.

Blueprint for resilience

In 2022, one of the UK’s largest water companies, Severn Trent Water, embarked on a multi-million-pound project in Mansfield, Nottinghamshire. The Mansfield Sustainable Flood Resilience project aimed to implement a large-scale sustainable drainage system (SuDS) to use nature-based approaches to alleviate flood risk and improve water quality and water management within an urban environment.

Real-time water level data ... supports sophisticated hydrological analysis and modelling, providing a deeper understanding of the system's behaviour under varying conditions

Metasphere’s radar-equipped level sensor was selected to monitor water levels within key components of the Mansfield SuDS scheme, including bioswales, detention basins and specific points within the sewer network. This provided Severn Trent Water and their academic partners with a clear and accessible overview of water levels.

The real-time water level data captured by the monitoring enables accurate calculation of drainage volumes and supports sophisticated hydrological analysis and modelling, providing a deeper understanding of the system's behaviour under varying conditions.

The Mansfield SuDS scheme started in spring 2022 and will complete in 2027, when the scheme is expected to have capacity to store over 58 million litres of surface water. This substantial increase in storage volume is projected to deliver a significant reduction in flood risk for approximately 90,000 of Mansfield's 109,000 population.

Actionable foresight

Drawing on the Mansfield project, scaling similarly successful SuDS projects across the country will require an advanced analytics platform that can quantify the volume of stormwater expected to enter the network, and identify where green interventions will yield the highest hydraulic benefit.

Utilities need to specify for a system that disaggregates complex sewer level data to a degree that isolates the specific signatures of infiltration and inflow - allowing asset managers to move away from stochastic modelling. Multiple benefits accrue from getting a handle on I&I – less raw water flowing in pipes not only frees up space for wastewater, but also reduces the cost, carbon and capacity required for pumping and treatment.

By quantifying the exact hydraulic impact of I&I, utilities can move from carbon-heavy infrastructure projects to low-carbon, nature-based solutions and a utility fit for a resilient future.

Ryan Pearson is head of strategy at Metasphere, a Grundfos company