How South Bend Saved $450 Million With 120 Sensors
In 2011, South Bend, Indiana faced a problem that thousands of American cities know well: a federal consent decree demanding billions in sewer infrastructure improvements. The EPA wanted the city to build massive underground tunnels and storage tanks to stop combined sewer overflows (CSOs) from polluting the St. Joseph River.
The estimated cost? Over $800 million — for a city with an annual budget of roughly $300 million.
Instead of building tunnels, South Bend tried something nobody had done before. They installed 120 sensors throughout their sewer system and created what essentially became a commodities market for wastewater flow.
The result: a 70% reduction in CSOs and $500 million in avoided capital costs.
The Problem: Combined Sewers and Consent Decrees
Like many older Midwestern cities, South Bend has a combined sewer system — meaning stormwater and sewage flow through the same pipes. During heavy rain, the system overflows, sending a mix of rainwater and raw sewage directly into the St. Joseph River.
These combined sewer overflows (CSOs) are a violation of the Clean Water Act. In 2011, the city entered a consent decree with the EPA requiring dramatic reductions in CSO volume. The traditional approach — the one consultants recommended — involved building massive deep tunnel storage systems, similar to what Chicago and Milwaukee had done.
The problem: South Bend couldn't afford it.
The Insight: Pipes Have Spare Capacity
South Bend's leadership, working with researchers at Notre Dame and technology partner EmNet (now part of Xylem), had a critical insight: during any given rain event, not all pipes overflow. Some parts of the network are overwhelmed while others have spare capacity.
If you could see what was happening in every pipe in real time, and if you could move flow from full pipes to empty ones, you could prevent overflows without building a single new tunnel.
"We realized we had a $1 billion network of pipes that we were only using a fraction of. The problem wasn't capacity — it was visibility and control." — Former South Bend Chief Innovation Officer
The Solution: 120 Sensors and Real-Time Trading
South Bend deployed 120 sensors throughout their 450-mile sewer network. Each sensor measures flow rate and water level continuously, transmitting data every few minutes to a cloud-based analytics platform.
The platform runs a real-time hydraulic model of the entire network, showing operators exactly where capacity exists and where overflows are imminent. Automated controls — gates and valves at key junctions — can redirect flow from overwhelmed pipes to pipes with spare capacity.
The system essentially created a real-time marketplace for pipe capacity. When one part of the network is "full," flow is "traded" to parts that are "empty." The concept mirrors how commodities markets work — dynamically matching supply (pipe capacity) with demand (stormwater flow).
The Results
The numbers speak for themselves:
- 70% reduction in CSO volume — roughly 1 billion gallons per year of prevented overflows
- $500 million in avoided capital costs — no tunnels, no massive storage tanks
- Real-time visibility across 100% of the network for the first time in the system's history
- Predictive capability — the system can predict overflows hours before they occur
- EPA approval — the consent decree was modified to accept the smart sewer approach
Traditional approach: $800M+ for deep tunnel storage
Smart sewer approach: ~$300M total (sensors + RTC + some targeted gray infrastructure)
Savings: $500M+
The Technology Stack
South Bend's smart sewer system consists of:
- 120 sensor stations — Ultrasonic level sensors and electromagnetic flow meters installed in manholes and key pipe junctions
- EmNet RTC platform (now Xylem) — Cloud-based real-time control and analytics software
- Automated gates and valves — At 8 key control points throughout the network
- Weather integration — Real-time radar data and forecast models
- SCADA integration — Connected to the city's existing control systems
Lessons for Other Cities
South Bend's experience offers several key lessons:
1. Start with Data
You can't optimize what you can't see. The first step is always installing sensors to understand how your system actually behaves during storms — which is almost always different from what engineers assumed.
2. Existing Infrastructure Has Hidden Capacity
Most sewer systems have more capacity than operators realize. Real-time monitoring reveals that many pipes are underutilized during storms while a few bottlenecks cause overflows. Redistributing flow is far cheaper than building new capacity.
3. The EPA Is Open to Innovation
South Bend's consent decree was successfully modified to accept smart sewer technology as a compliance strategy. The EPA has since published guidance encouraging other cities to consider similar approaches.
4. Small Cities Can Lead
South Bend has a population of just 103,000. You don't need to be a major metropolis to deploy smart sewer technology — and the ROI is often even more compelling for smaller cities with tighter budgets.
What Happened Next
South Bend's success inspired a wave of smart sewer deployments across the Midwest and beyond. Cities like Louisville, Grand Rapids, Evansville, and Fort Wayne all launched their own programs, collectively saving over $1 billion.
The technology has also evolved. Today's platforms offer more sophisticated AI models, better sensor hardware, and lower deployment costs than what South Bend pioneered a decade ago. What was revolutionary in 2012 is now approaching standard practice.
See all tracked deployments on our City Tracker, or explore the vendors building this technology.