Utilities around the world are replacing short-term studies with continuous network visibility, uncovering wet weather loading that influence treatment costs, rehabilitation priorities and capital projects, while proving for the first time if remediation is working.

A utility in the US we're working with is facing a $350 million treatment plant expansion.

Under their current arrangement, the utility holds a license to divert peak wet weather flows rather than treat them, but the new plant removes that option. Once commissioned, every gallon arriving at the plant must be treated, which means the extraneous flows previously bypassed during storms now become a treatment burden.

This leaves the utility with two options: spend up to $80 million on additional storage infrastructure or significantly reduce the wet weather loading entering the network in the first place.

Before a decision was locked in, the wastewater manager asked: What would a measurable reduction in I&I change?

If I&I accounts for 40 percent of wet weather influent, which sits comfortably within the range seen across many US wastewater networks, the plant is processing roughly 1.4 billion gallons of extraneous flow annually.

Even a five percent reduction removes around 70 million gallons from the treatment burden every year. At EPA operational benchmarks of roughly $2 to $5 per thousand gallons treated, that represents up to $350,000 annually in avoided treatment cost. But the more important number is what peak flows are doing to the size of the infrastructure being designed around them.

Treatment plants are sized for extremes and I&I is often one of the largest drivers of those extremes.

For this utility, a storage facility costing tens of millions of dollars may either be a genuine operational necessity or a contingency being priced in because the network visibility is not strong enough to confidently argue for the alternative.

That is the shift permanent monitoring creates. It reduces uncertainty before major operational and capital decisions are made.

Utilities in Australia, New Zealand and Europe are already making the shift, using continuous visibility to guide rehabilitation programs, validate capital projects and quantify treatment impacts over time.

Temporary studies were never designed for this

In much of the US, temporary studies still remain the dominant approach. While they have served the industry well for decades, they were built around technology constraints that no longer exist and they don't generate the continuous network data that modern AI-driven platforms can now use to surface patterns and predict behavior.

I&I programs have been restrained by the practical limitations of the monitoring hardware for decades.

Flow studies were temporary because batteries only lasted months, network-wide visibility wasn’t practical because servicing overhead was too high, and investigation programs were expensive and built around experience because there was no continuous data to guide them.

As a result, many US utilities built I&I programs around snapshots of network behavior rather than continuous understanding.

But those hardware limitations have largely disappeared and what has replaced them changes the model entirely.

Kallipr's permanent flow monitoring solution installed in a wastewater network in the US

Why that’s changed

Part of the foundation is the network. Low-power wide-area cellular technologies (NB-IoT and Cat-M1) are already deployed at scale across the US by T-Mobile, Verizon and AT&T, purpose built for exactly the kind of low-signal, underground environments that defeated earlier cellular generations. T-Mobile has committed to maintaining its NB-IoT network until at least 2035.

On top of that network foundation, a new generation of chipsets and power management architecture has shifted what is achievable in field.

Devices that previously required battery changes every few months can now operate up to ten years without intervention. And when batteries do reach end of life, they can be swapped in-field with no compromise to the device.

Sensors that previously needed external antennas mounted on the outside of manholes now operate with internal antennas that function reliably from inside the pit.

Installation that previously required specialist equipment, extended site time and in many cases confined space entry can now be completed in under thirty minutes by a standard field crew via a mobile app.

The cost profile has shifted accordingly. The per-site economics of permanent deployment at network scale are a fraction of what they were five years ago, and the servicing overhead that made large permanent networks operationally unsustainable is gone.

You can’t schedule a flood

The biggest limitation of traditional I&I programs was the visibility window.

Temporary studies only capture the network for a short period of time and wet (especially extreme wet) weather behavior does not conveniently occur on schedule.

A temporary study that doesn't capture a significant rainfall event during its deployment window produces data that is at best incomplete, and there is no mechanism to guarantee the rain you need will fall during the weeks your meters are in the ground.

That is why permanent monitoring changes the model so significantly.

Instead of trying to catch wet weather events during isolated study periods, utilities can now leave monitoring infrastructure in place continuously and build a long-term behavioral understanding of how the network actually responds over time.

What permanent I&I monitoring actually looks like

Permanent level sensors are deployed broadly across the network at sub-basin boundaries, key manholes and catchment entry points. Rainfall data is layered over the top to continuously profile how different parts of the network respond during and after wet weather events.

Where direct flow measurement is not practical, level data combined with Manning’s equation provides reliable relative flow estimation across catchments. Utilities can quickly identify which areas are disproportionately contributing to wet weather loading before committing crews, CCTV inspection or rehabilitation funding.

Flow monitoring is then concentrated at the locations where accurate volumetric measurement matters most, including pump stations, interceptors, major junctions and treatment plant inlets.

For the first time, operators can continuously connect rainfall intensity, catchment response, groundwater-driven infiltration, peak flow contribution, treatment plant loading and rehabilitation outcomes into a single continuous picture.

Most importantly, utilities can now prove whether intervention programs are actually working.

A lot of utilities know their total I&I number but still can’t confidently tell you which catchments are driving it or whether rehabilitation is reducing the load. It becomes a serious problem when major capital decisions are being made off incomplete visibility.

Most utilities already have surrounding infrastructure in place like SCADA, GIS, rainfall data, hydraulic models or work management platforms. Permanent monitoring now integrates into these environments without a transformation project.

Kallipr dashboard showing inflow & infiltration on a sewer network

What continuous monitoring is revealing

In New Zealand, a utility with our permanent monitoring installed across part of their network identified groundwater-driven infiltration that behaved nothing like traditional inflow.

Rainfall was recharging the aquifer, increasing subsurface pressure and forcing groundwater into the network gradually over weeks rather than hours. The result wasn’t a sharp wet weather spike but a sustained loading condition that continued long after rainfall stopped.

A temporary study would never have captured the full behavior.

That discovery changed how the utility approached the problem. The issue became understanding how entire catchments behaved under changing environmental conditions and what that sustained loading was costing at the treatment plant.

Permanent monitoring becomes a way to continuously understand how the network behaves as a system.

Permanent monitoring changes rehabilitation programs

This is where the operational model starts to shift.

Historically, rehabilitation programs were often prioritized using a combination of historical knowledge, isolated flow studies, CCTV findings and reactive investigation.

But rehabilitation is expensive. Pipe relining alone can cost around $800,000 dollars per mile and utilities can spend significant capital without clearly quantifying the impact on network performance afterwards.

Permanent monitoring changes that.

Utilities can now establish pre-rehabilitation baselines, measure wet weather response before and after intervention, quantify reduction over time, compare catchment performance continuously and prioritize future rehabilitation based on measured contribution rather than assumption

That creates a level of accountability and confidence many utilities have never had before.

Instead of treating I&I as a recurring investigation program, it becomes an ongoing performance management process.

What happens next

Permanent monitoring is already standard practice for utilities across the globe. Kallipr alone has deployed continuous I&I monitoring solutions across utilities globally, many of whom are now onto their second generation of devices having proven the model and expanded their programs on the back of it. In the US, we are currently working with over 40 utilities on exactly this challenge.

The gap in outcomes between utilities running permanent monitoring and those still relying on periodic studies is becoming visible in rehabilitation programs that can demonstrate measurable flow reductions, in capital projects sized on network evidence rather than conservative assumptions, and in treatment costs that are moving in the right direction for the first time.

For US utilities, the window to get ahead of this is narrowing. As permanent monitoring becomes the expected standard, regulators, ratepayers and capital planners will increasingly ask for the kind of continuous, verified evidence that temporary studies cannot produce.

For the utility facing that $350 million expansion, the opportunity is clear.

Before the plant is finalized, before storage infrastructure is committed and before long-term operational costs are locked in, there is now an opportunity to answer a question that historically could not be answered confidently:

How much of the peak demand entering the plant is actually avoidable?

If the answer changes the peak flow calculation by even a few percentage points, the capital implications are enormous.