How South Bend got smart about water quality
For South Bend, Indiana, a complicated water quality issue required a smart approach — a smart sewer system to be precise
Like many older municipalities in the United States, South Bend, Indiana, has had its fair share of infrastructure struggles, particularly when it comes to its aging sewer system.
What began in the latter half of the nineteenth century as a rudimentary approach to keeping city streets free of both stormwater and the unwanted refuse that went along with it has largely been left in place over the years and incorporated into modern sanitation practices.
This means that in South Bend — and in more than 800 other communities across the country — both human waste and stormwater flow into the same collection system.
But there’s a catch (aside from the obvious concern over century-old pipes) — the system was never meant to handle the volume of wastewater from a city of 100,000 people let alone the hundreds of millions of gallons of stormwater that can accumulate during a one-inch rainfall event.
In fact, South Bend’s sewer lines were only designed to carry the maximum dry weather amount of flow, no doubt as a result of decades of retrofitting rather than more substantial — and prohibitively costly — renovations.
And as a recent case study points out (which can be reviewed below), this was a recipe for disaster:
Prior to 2008, the sewers would overflow into the Saint Joseph river virtually every time it rained — overflows of some 1 to 2 billion gallons or more annually.”
This obviously wasn’t a good scenario for the community — research has shown that gastrointestinal ailments spike in the aftermath of combined sewer system overflows (CSOs), stemming from the large quantities of E. coli and other harmful bacteria released into recreational waterways and drinking water sources.
And this certainly wasn’t an ideal scenario for the city government, who had to figure out a way to pay for the much needed — and as of December 2011, federally mandated — upgrades.
South Bend’s Smart Sewer Program Is Born
Beginning in 2008, the city started tackling this problem with a decidedly high-tech solution -- in partnership with Enmet, they began installing data collection sensors throughout the sewer system so they could better understand what was happening underground.
The more information you have about your sewer system, the better,” said Kieran Fahey, director of the city’s long term sewer control plan. “If you know where the blockages are, for example, you’re not waiting on reports [from the field]. You’re actually going in in advance because you’ve basically got eyes in there.”
But South Bend’s new smart sewer project didn’t stop there. By 2013, the city had installed nine controllable valves, three movable weirs and six rain gauges throughout the system in addition to the approximately 150 sensors that monitor 111 different locations.
Despite this complex technology, the way the system works is rather straightforward: Trunk sewer lines collect wastewater from the various regions of the city and then feed it into larger interceptor lines via throttle pipes. It’s within these throttle lines that the controllable valves operate, adjusting access to the interceptors based on need.
Prior to this system, heavy rains would overwhelm the connecting lines between the neighborhood sewers and the interceptors, resulting in CSOs, Fahey explained during a phone call a few weeks ago.
We have 40 square miles in South Bend so it’s obviously not a huge city,” Fahey said, “but it’s a fairly big footprint for a city just over 100,000 people. This means that you could potentially have a thunderstorm or just any kind of rain event in one part of the 40 square miles that you wouldn’t have somewhere else, so that creates an opportunity for you.”
“So we put in the throttle pipes and controllable valves, which are able to manipulate how much access to the interceptor the neighborhood sewer line gets,” he continued. “The pipes that are about to overflow get priority access to the interceptor, which means they don’t overflow.”
And this investment certainly paid off.
“We still have a high number of overflow events,” Fahey explained, “like 60 to 70, but they’re much diminished in regard to the quantity of material. An overflow previously might have been 200 million gallons, but now an overflow might be 5,000 gallons.”
These smaller overflows add up to a major environmental boon — a reduction of more than 1 billion gallons of untreated sewage flowing into the river annually.
“And that’s just in the volume of CSO,” he continued. “We’ve had a big reduction in the geometric annual mean for E. coli as well, which is the big parameter of concern for all this. Before the project started, we had 430 colony forming units per 100 milliliters, and now we’re down to about 180.”
While the overall price tag of the project was around $6 million (plus $280,500 annually for data collection, operations and maintenance), this pales in comparison to cost of the upgrades the U.S. EPA wants the city to make — upgrades that the city believes are no longer necessary given the substantial improvements they’ve seen.
They believe they have a better way forward, building on this success using what’s made it all possible — the data.
Showdown With the EPA
Using 12 million hours of data collected by their system over the years, the City of South Bend, in conjunction with Enmet and other private partners, set out to create a better plan for getting their combined sewer system (CSS) in line with EPA regulations.
Mr. Fahey was hired in 2015 to manage this process. While South Bend had committed to a plan through a formal consent decree signed in late 2011 — the last day of Mayor Pete Buttigieg’s predecessor, to be exact — many in the community, including the new mayor, questioned its feasibility.
That’s because it required the city, with a median household income of 35% less than the rest of the U.S., to make a variety of upgrades to the tune of more than $700 million.
“If you buy something like a house for $700 million,” Fahey explained, “you of course pay a mortgage, which adds like three, four percent on top of that every year. Now the cost of the project is over $1 billion.”
"$1 billion is basically $10,000 for every single man, woman and child,” he continued. “So that was really our motivation to come up with an alternative. When you have a plan that you can’t afford, you essentially have no plan at all.”
The new plan, which the city is still negotiating with the EPA, uses the existing smart sewer system and the installation of new green infrastructure to offset the need for more costly projects, like underground storage tanks and a new interceptor sewer.
“Previously we were modelling under a lot of assumptions and uncertainty,” Fahey told GWI in 2017. “In some places the plan was saying we needed storage tanks that would have each cost $60-70 million, and now with the much more accurate model that we have based on real-time data, we know that some of these aren’t required at all.”
They also know that the EPA’s plan will not get the city to the required limit of no more than four overflows per year.
“Based on the information we’ve gathered through the smart sewer system,” Fahey said, “we now know that the plan would actually result in 13 CSOs per year, so that’s definitely part of the negotiation.”
The city is also keen to point out that their plan — the smart sewer project is not currently part of the consent decree — has been doing the trick.
“Even though we have yet to undertake 90% of the work prescribed to us, we’ve seen a 75% reduction [in CSO],” Fahey explained. “And 84% of the reduction in E. coli is due to work completed on our own.”
And the new price tag is definitely right — by the city’s calculations, it would only cost $200 million in upgrades for the system to be in CWA compliance.
While the negotiations are progressing slowly, Fahey is optimistic that the updated plan will be approved soon, possibly by the end of the year.
We have to do a lot of education [with the regulators] because what we’ve done in South Bend is pretty novel,” Fahey said. “We’re also trying to make them realize that this is a gamechanger, and not just for South Bend. This is a solution we believe they should take to other communities as well.”
Learn more about South Bend’s smart sewer system: