(TNS) — SOUTH BEND, Ind. — About 80 times a year, raw sewage in the city’s combined sewers overflows into the St. Joseph River during periods of heavy rain or snowmelt. That’s when the “smart sewer system” kicks in, using wireless sensors to redirect the flow of that sewage from the river as much as possible.
But during the flood here in late February, officials say, Mother Nature prevented that technology from doing its job.
Although the system worked well during the historic flood here in August 2016, it didn’t this time because the river level sharply rose to fill the city’s more than 100-year-old combined sewer system, said Eric Horvath, the city’s public works director.
Once the river reached a certain level, sensors beneath manhole covers could no longer be used. The mixed stormwater and sewage had nowhere else to go but into the river.
“When you have the river come up and completely overwhelm your system,” Horvath said, “there’s nothing you can do to fight Mother Nature.”
The city’s smart sewer system was designed by EmNet, a water-management company in South Bend that was launched in 2004 under a partnership with the city, University of Notre Dame and Purdue University.
The city spent $6 million on the system, which features a network of sensors, valves and gates that detect blockages in pipes. Sensors monitor water levels during overflow events, opening and closing valves to redirect wastewater from blockages.
Tim Braun, enterprise architect for EmNet, said that during the early stage of the recent storm, the smart system ensured the “first flush” of runoff from streets was treated at the plant before sewers were “inundated” by floodwaters.
The system has continued to collect wastewater data that could help the city take lessons away from what happened, Braun said. And as the river level recedes, the system will help correct the ongoing problem of raw sewage dumping into the river.
The city’s wastewater treatment plant was briefly shut down last week because of on-site flooding. Horvath said it is now operating at less than three-fourths of its peak treatment capacity of 77 million gallons per day. For the plant to run at full capacity, the river level will need to drop more.
In the meantime, millions of gallons of raw sewage continue to run through the city’s 35 combined sewer overflow points along the river. Overflows happen when the combined sewer system, which handles storm and wastewater, becomes overwhelmed. (As long as certain rules are met, the state allows municipalities to send raw sewage into public waterways.)
Horvath said that although the plant is treating all of the sewage from sanitary-only sewers, less than a quarter of the wastewater from combined sewers is being treated. Combined sewers make up about half of the city’s sewer system; sanitary-only sewers, which collect sewage but not stormwater, account for the other half.
The city’s investment in the smart system has resulted in savings by eliminating about “a billion gallons of overflow a year from our river,” Horvath said.
“The system’s cost is a fraction of what it would cost to build tanks and bigger sewers, because we’re optimizing the flow that goes through sewers we’ve already paid for,” he said.
EmNet is contracted by the city to help run the smart system. In December 2017, the city’s Board of Public Works approved a new three-year contract that calls for the firm to be paid $280,500 annually for services such as data collection andmaintenance.
The city, meanwhile, is taking steps to reduce combined sewer outflows as part of a long-term control plan mandated by the U.S. Environmental Protection Agency.
The city signed off on a “consent decree” in 2011 with federal regulators that requires it to spend hundreds of millions of dollars on sewer system upgrades to comply with the federal Clean Water Act. The goal of the long-term project is to reduce the annual number of combined sewer overflows to no more than four by 2032.
The city, which has already spent nearly $150 million on upgrades as part of the mandated project, is now focused on cutting future costs.
Last year, the city started negotiations with state and federal regulators to seek approval to revise the project by modifying the 2011 consent decree. The remaining cost of sewer upgrades would drop from about $713 million to $200 million under the plan, but environmental goals would still be met.
Data collected over the past decade by the smart sewer system was used to design a more affordable project, said Kieran Fahey, director of the city’s long-term control plan.
Fahey said the original plan called for building seven storage tanks and two tunnels, but the proposed one calls for three storage tanks and nearly 20 acres of “green infrastructure” to prevent overflows, such as “rain gardens” along streets and porous concrete in certain areas.
Negotiations with regulators will continue this year and possibly into 2019, said Fahey, who is optimistic the project will be a success.
“We’re hopeful the solution we’re coming up with can be applied in other communities,” he said.
©2018 the South Bend Tribune (South Bend, Ind.) Distributed by Tribune Content Agency, LLC.