The City of South Bend, Ind., is turning to an array of sophisticated sensors, among other technological innovations, to expand the capacity of its storm and sanitary sewer systems and make existing infrastructure more efficient.
Several years ago, South Bend's biggest challenge involved combined sewer overflows. On average, more than 2 billion gallons of untreated sewage was discharged into the St. Joseph River during 80 events per year.
"This is not just a problem faced by South Bend, but by hundreds of cities across the country," says Gary Gilot, P.E., president of the South Bend Board of Public Works and consultant with the city's Public Works Department.
Portions of the sewer and stormwater system are showing their age. Some clay tile pipes are approaching the century mark, while reinforced concrete, ductile iron or cast iron are heading for 50.
South Bend examined a number of options to control CSOs, including sewer separation and the construction of large storage tanks that would allow the wastewater plant to treat excess water over several days.
"However, what caught our eye was research we saw at Notre Dame in 2005 that used embedded sensors to conduct real-time monitoring and control of wastewater and stormwater," says Gilot.
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Embedded sensor array
Developed by engineers and scientists at Notre Dame and Purdue universities, the system employs a series of embedded sensors coupled with battery-powered, credit-card-sized computers. The sensors use mixed 900 MHz cellular service to transmit data every five minutes.
"I saw a bench-scale hydraulic model in the laboratory and Michael Levine, a professor at the Department of Statistics at Purdue, had taught it to make decisions based on an economic model," says Gilot. "It would route the stormwater from each simulated storm at the lowest price, with a low price associated with water being sent to stormwater basins, and higher prices for water going into the river or someone's basement."
EmNet, a startup company formed by Notre Dame graduate students, developed and marketed the sensor network as CSONet. The city began to install the system in mid-winter 2008. EmNet reports that, as of the beginning of 2013, it had supplied 117 manhole cover-mounted sensors at CSO outfalls, interceptors, trunk lines and retention basins at a total cost of about $3 million.
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The city already employed a SCADA system that monitored the system at 17 locations — primarily lift stations — using Rockwell Automation's RSView software.
The missing element was a system that could crunch all of the data, present it to Public Works staff in a usable form, and then translate that information into instructions that would achieve the department's operational goals.
Enter IBM's Intelligent Operations Center (IOC) for Smarter Cities.
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"We were working with EmNet and they introduced us to Gary Gilot and Patrick Henthorn, South Bend's assistant city engineer," says Carey Hidaka, a public sector business solutions professional with IBM Global Business Services. "We knew that in a lot of organizations, data collected from a water or wastewater system is siloed. We wanted to free that data to do as much work as it could and help South Bend become a data-driven city."
The computer-screen dashboard developed by IBM provides a color-coded representation of the system in real time, allowing staff to focus infrastructure resources to control impacts on the receiving stream. Similar to a traffic light, green is good, yellow means caution and red indicates an emergency.
The system also incorporated other readily available information from sources as diverse as the National Weather Service, the U.S. Geological Survey and the Na-tional Oceanic and Atmospheric Administration.
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A cloud system first
Once developed, IBM moved the entire system to SmartCloud, its cloud-based service. That strategy eliminates the capital cost of IT infrastructure, and allows the city to pay for the service from its operational budget. It also allows the data collected to be used by any authorized city employee.
"To the best of our knowledge, this is the first time a wastewater collection utility has hosted its monitoring system on a cloud service," says Hidaka.
As the system was built, the department looked at its system with a fresh perspective.
"It used to be considered a reasonable assumption for any system that rainfall was uniform," says Gilot. "But between the sensors and radio-enabled rain gauges, we were able to demonstrate that we might be experiencing a drizzle on the east end of town and a downpour on the west. We also know the exact daytime flows versus the higher morning and evening peak flows when people are home. Knowing this information, the sensors can talk to each other and to the department's SCADA system, as smart valves direct excess flows to parts of the system that are most capable of accommodating the extra volumes. This is such a far cry from the old days when we'd have two guys who were CSO inspectors flipping sewer lids until they discovered the problem."
The genius of the system is its ability to capture new information, such as basement flooding reports, and display them in such a way as to direct the department to action. A basement flooding "heat map," for example, shows hot spots where more incidents of basement flooding have been reported, directing repair and maintenance crews to expend more effort there.
"The IBM Intelligent Operations Center for Smarter Cities is agnostic," says Gilot. "It can take data from CAD drawings, treatment plant rain gauges, sewer sensors and anything else we care to feed it and boil it down to useful information that allows us to make decisions at a glance."
The system can also work to prevent any accidental overflows resulting from routine procedures such as flushing hydrants.
"Imagine you're in a storm and your water utility picks that time to backwash its filters on schedule," says Gilot. "That data is now part of the overall system, and the logic linkage can override that backwash procedure until the storm is cleared, allowing us to avoid shooting ourselves in the foot."
An IBM super-computer was also used to run years worth of rainfall and combined sewer overflow simulations to determine which methods could be used to reduce CSOs at the lowest cost.
"It turns out that planting native plant species with deep roots helps to draw rainwater into the aquifer for far less money than big pipes," says Gilot. "We've got to think of rainwater as a resource to recharge the aquifer and not something we've got to shunt away from the city."
However, no matter how much computer power is thrown at the system, the conscientious efforts of department staff and crews remain essential to reaching and maintaining optimal system efficiency.
A CUES van provides crews with CCTV support while five Vactor and Vac-Con sewer cleaning units clean catch basins yearly and the entire system every four years. The city is looking at purchasing a sixth, smaller unit that is more maneuverable in tight locations.
Crews more efficient
"Instead of sticking primarily to a routine pattern, they're accessing the data system to see how well they're performing in real time," says Gilot. "If they see an area that needs attention after a storm, they move their crews to that area to remove grit and debris first. This is something they're doing on their own initiative."
Using the new system has made the department so efficient that existing crews now devote 50 extra days per year to clean sewers, clean 2,000 additional catch basins annually, and have increased the number of sewer inspections at non-routine locations by 175 percent.
The Environmental Protection Agency and South Bend agreed to a consent decree in December 2011. Under that agreement, the city will invest more than $500 million over 20 years to reduce CSOs by 95 percent.
"We essentially told the EPA that we believe we've developed a better mousetrap that will save our ratepayers money," says Gilot. "The EPA was open to our idea with the proviso that if we couldn't make our case, we were back to Plan B, spending more than $500 million on a storage solution."
However, the current steps taken by the city to address CSOs have already made significant strides toward those goals. Wet-weather overflows have been reduced by 23 percent and dry-weather overflows have been reduced from 27 occurrences to one in the system's first full year of operation. By mid-2012, it was estimated that simply using existing infrastructure in a more efficient way has helped the city avoid more than $600,000 in potential government fines while potentially offsetting more than $100 million in capital infrastructure cost.
The system is already helping to transform South Bend into the data-driven city it aims to be. Solid waste trucks, for example, are now being fitted with Wi-Fi devices to collect water meter data. Police can access a list of properties that no longer have water service and flag those as abandoned nuisance properties that may attract crime.
South Bend mayor Pete Buttigieg says he routinely boasts about the city's advanced wastewater treatment system when promoting the community.
"The wastewater system is one of the most technologically advanced in the country," says Buttigieg. "Of course I want to tell people about it. It's part of the leading edge of development that's transforming South Bend into a digital city."
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