Early mistakes along the way in the City of Peoria’s combined sewer overflow projects will likely mean a $200 million increase to the bill for the multi-year, federally mandated process.
According to a presentation given to the Peoria City Council at a special policy session Tuesday, one of those miscalculations lies in the approach originally chosen to remedy the sewer overflow issues that led the city into a consent decree with the U.S. Environmental Protection Agency [EPA] and the Illinois Environmental Protection Agency [IEPA] in late 2020.
Peoria was originally found to be in violation of the Clean Water Act due to wastewater in the Illinois River in 2006.
Initial considerations for sewage storage had three primary storage types: Green infrastructure, in-system storage and offline storage. Designers primarily focused on green infrastructure, storing and infiltrating storm water after it falls, as the most cost-effective approach at the time.
Examples of green infrastructure include permeable pavers in parking lanes, porous asphalt and stormwater bump-outs to allow the water to absorb into soil before entering sewer systems.
However, Tuesday's presentation notes the use of green infrastructure and initial engineering and design relied partially on early tests showing soil below Peoria’s bluffs was sandy and permeable.
“We did do due diligence. We had a pilot project and we did some advanced infiltration testing and those results were very positive,” said city engineer Andrea Klopfenstein. “But when we went in to do more detailed testing, we found that the soils were different.”
Klopfenstein says that creates a problem with green infrastructure projects. They need to deposit wastewater where soil is permeable. So, if the soil isn’t permeable, either the infrastructure needs to be moved, there needs to be more projects, or the water needs to be piped from the green infrastructure to where permeable soil lies below the surface.
In general, the presentation calls the engineering shift’s impact a “two-year plus lag in adapting to lessons learned from project performance.”
The soil tests aren’t the only early decision creating speed bumps as the project progresses.
Klopfenstein says maintenance of the green infrastructure has also proven more costly than initially expected. Maintenance crews are spending more time clearing street debris from the storm water inlets than predicted.
“We’ve also had long lead times for getting new equipment to help with maintenance. It took us over three years to get a regenerative air street sweeper, which at the time when we first started this project was unheard of,” said Klopfenstein, pointing to supply chain issues emerging from the COVID-19 pandemic as a cause for the delays.
Klopfenstein offers an example of a third reason green infrastructure projects have been more expensive than expected is “rolling in” the cost of co-benefits to the projects themselves.
“Instead of doing an ADA [Americans with Disabilities Act] ramp, putting the green infrastructure under the ADA ramp and having the sidewalk funds pay for the ADA ramp, the cost of the ADA ramp is going into the combined sewer overflow loan, so that’s adding to the cost,” said Klopfenstein.
Despite the setbacks, Klopfenstein stresses the green infrastructure is working as intended. Four years of the green projects have accomplished “Milestone 1,” the first of four checkpoints over the 18-year process required by the consent decree.
The policy session presentation suggests early estimates for the suite of projects at $109 million didn’t factor in inflation. Adjusted for 2025, the original total is closer to $136 million, partially driven by the lingering effects of the COVID-era supply chain disruption.
After factoring in inflation and the rising cost of construction materials, a new projection provided by city staff places the projects’ cost at $338 million – more than three times the initial estimate.
The final repayment cost will also depend on how the city chooses to finance the projects long-term, whether they take a 30-year loan through the IEPA (about $409 million) or continue funding the projects through 30-year bonding (more than $660 million.)
For Peoria-area residents, that means a rate increase on sewer rates over the next few years. The presentation indicates staff plan for rate increases to start in 2027 and cover both the city sewer and the Greater Peoria Sanitary District.
Depending on the financing model the city chooses, the higher rates could mean the average sewer bill increases from $69.45 per quarter to as much as $98.05.
In the meantime, the projects are required by the consent decree and must continue.
Klopfenstein says, heading into Milestone 2, the city is considering moving an offline storage, or storage outside of the sewer system, project forward.
She says moving to "grey" infrastructure, while still using green infrastructure when there’s a good opportunity, should be more cost effective in the long run.
The Milestone 2 project recommendation, which Klopfenstein says should also satisfy some of the requirements of Milestone 3, is a massive 6.4 million gallon tank on the riverfront near the Cedar Street Bridge to store stormwater overflow.
An estimate in the city’s presentation places the cost of the Cedar Storage project around $60 million, while continued green infrastructure to meet the requirements of Milestone 2 are estimated at “$102 million or more.”
Klopfenstein says the tank is the largest of five planned over the full 18-year program.
“We’re just completing our feasibility study to help us determine that it would work and where it could potentially go,” she said. “We know it’s the largest tank. We’ve got some cost estimates. We’re still investigating.”
Klopfenstein said moving into the design phase will mean determining whether the tank will be above or below ground.
As the city wraps up the last of the green infrastructure projects in 2025, the earliest construction could start on the Cedar Street tank is 2027.
