How Good Data Made an Entire City Cleaner
South Bend Sewer System / Case Study
The City of South Bend, Indiana has a sewer system that’s over 100 years old. Expanded intermittently and unevenly through its history, the system is a complex patchwork of different materials, models and mechanisms. Its technology conflates several eras of engineering. Its pipes have weathered for decades. Its architecture is a labyrinth of twists and turns.
Over the years, the system has only become more complicated. Originally built to carry rainwater and snowmelt away from the town center, it was later repurposed to accommodate indoor plumbing. Then, in the 1950s, it was again adjusted to include the city’s first wastewater treatment plant. As it stands today, the system has one long central pipeline that serves both sanitary waste and stormwater, bringing these to the wastewater treatment plant for processing.
But it’s not so simple as that. Because the system uses a single line (a “combined sewer”) for both plumbing waste and precipitation, the flow of wastewater is sometimes too much for the treatment plant’s capacity. When that happens, the result is a Combined Sewer Overflow. Any wastewater above a certain flow threshold falls into the nearby St. Joseph River.
One of Many Cities Challenged by Infrastructure
South Bend isn’t alone in facing the Combined Sewer Overflow (CSO) problem. Across the United States, 772 cities struggle with the issue. Most of these are older cities on the East Coast and in the Midwest, developed before the introduction of wastewater treatment plants. However, even some West Coast cities like Seattle are affected by CSO. And in Europe, where many sewer systems are centuries old, the problem becomes even more complicated.
Like most older cities, South Bend was never designed to handle so much wastewater. CSO events gradually became common. So common, in fact, that about 900 million gallons of waste would fall into the river each year. The City also frequently experienced Dry Weather Overflows (DWOs), which are each subject to a $27,500 fine from the Environmental Protection Agency.
Realizing the dangers posed by so much pollution, particularly the potential for harmful E. coli, the City has been working on an upgrades program for over 20 years. After recently analyzing the long-term remediation and improvements needed to prevent future DWOs, the City found it was facing roughly $400 million to fix the problem. Could it find a more cost-effective solution without compromising the health of South Bend’s community?
How to Get More Out of the Same Old Pipes
Carefully evaluating their choices, the City considered an unexpected option: real-time monitoring (RTM). The benefits of this type of system were twofold. Almost immediately, better information would enable more efficient management of the entire sewer line. With early warnings of anomalies and risk factors, the City could locate, understand and resolve many issues before they turned into overflows. And later on in the upgrades program, the system would help the City target specific areas for renovation and construction. The City could then focus its efforts on sections that needed the most attention.
South Bend quickly moved forward with this approach. It contracted a local company, EmNet LLC, among others, to equip and assist in planning the RTM system. The system’s initial launch would include 110 RTM locations along the sewer line: 36 at CSO sites, 27 along the interceptor that brought wastewater to the treatment plant, 42 along key trunklines, and 5 at retention basins. The City planned for each site to be supplied with a manhole-mounted LogiCover™ to transmit data from the instruments below. But this new system left one question unanswered: where would all that data come from?
The Final Piece to the Puzzle: One Reliable Sensor
A monitoring system is only as good as its data. Quality in, quality out. To make its system as effective as possible, the City needed trustworthy readings from its 110 monitoring sites. This demanded a sensor that would satisfy three key criteria:
The conditions within the sewer system present maintenance challenges. Buildup of grit and grime can interfere with the exposed sensor cone, leading to erratic readings. And because many of the monitoring sites are at intersections, inspecting and cleaning a sensor can have a major impact on local traffic.
2. Low Power Consumption
Maintenance crews can accomplish far more when they don’t have to replace 110 battery packs every month. Often at capacity already with work orders for fixing bottlenecks and inspecting anomalies, they needed a sensor that would endure long-term deployments.
The City wanted to act on its data, not be lost in a sea of uninterpretable figures. With accurate information, the City could efficiently deploy teams to handle issues. An additional concern: temperature varies tremendously in South Bend. Due to these fluctuations, the City’s pressure sensors would have to retain their accuracy in a variety of temperature conditions.
So who would provide the sensors? And how could the City get a full shipment of them on its short timeline? After doing their research, the City found that INW’s PS98i was both a low-power solution that met their maintenance needs and a cost-effective instrument for the project. South Bend officials were also impressed with the sensor’s accuracy of ±0.1% FSO as well as its built-in thermal compensation.
Within three weeks, INW was able to fulfill an initial shipment of 98 sensors. Once installed, the City applauded the sensors’ resilience in the field. “We found them to be very robust and very reliable,” acclaimed Tim Ruggaber—EmNet’s Director of Operations—who managed the project. The sensors’ energy efficiency also exceeded expectations, resulting in an average life of 10 months for the battery packs.
Saving the City from Financial and Environmental Hardship
Before installing the RTM system, both the City and the St. Joseph River were facing major challenges. In 2008, the City’s 29 Dry Weather Overflows were liable for $797,500 in fines. The City also needed to budget hundreds of millions of dollars for capital improvement projects that included sewer renovations and infrastructure upgrades. At the same time, nearly a billion gallons of waste were flowing into the St. Joseph River each year.
With accurate information at its fingertips 24/7, the City has been able to instantly detect variations from baseline levels, free up personnel to perform maintenance, dramatically reduce its number of DWOs, and even identify key areas for renovation projects. The St. Joseph River has already experienced significant relief from much of the pollution. In 2009, total waste flowed into the river was reduced by 215.4 million gallons from the previous year.
Now the City can focus its efforts on prevention and problem solving instead of blind investigation. Over the last three years combined, only 12 DWO events have occurred throughout South Bend. The new data has also proven valuable to the City’s budgeting office, revealing $120 million that can be saved on capital improvements. According to South Bend’s Assistant City Engineer, Patrick Henthorn, “This system is well worth the money—both for the sensors and the Real Time Monitoring.”