Thornton administrator says help may be coming to alleviate stench from quarry reservoir

The Thornton Reservoir is known far and wide for providing many locals, and some passersby, with a lingering smell of sewage.

“I can smell it going down I-80,” said Thornton Village Administrator Doug Beckman of the Deep Tunnel reservoir, which has been online since late 2015.

But Beckman said the Metropolitan Water Reclamation District of Greater Chicago is now taking a proactive approach to address the odor concerns.

“They’ve been talking to us about different operational procedures to try to control it, but I think they finally realized they have to do more than that,” Beckman said. “They finally started investing some money.”

The investment comes from an expanded budget and recently signed contracts with outside companies. By January 2024, the odor neutralization system will be expanded at a cost of $1.05 million, said Allison Fore, the public and intergovernmental affairs officer for MWRD. This is on top of $1.3 million that was spent on a similar expansion when the reservoir opened.

MWRD also entered into a contract with Jacobs Engineering in June to have outside national odor experts evaluate its strategies to minimize odor complaints and address any identified gaps, Fore said.

MWRD executed another contract July 13, 2023, with OptimaBiome for $936,400 to test a biological-based product to naturally mitigate odors in 2024 and 2025.

In 2020, the water reclamation district commissioned a study to investigate the reservoir’s first several years of operation.

“Shortly after the reservoir went online, the MWRD immediately increased the number of solar aerators from seven to 20 to enlarge the oxygenated lens on the surface of the water in the reservoir to minimize odor releases,” Fore said. “The MWRD installed a state-of-the-art odor neutralization system at its nearby shafts to address the release of odors.”

The 2020 study found that “odor complaints appear to be trending downward.” That trend seems to be continuing. There had been few complaints this year with no one expressing displeasure with the smell between March and June.

But then in July, historic storms drenched the state causing flooding in some areas. Wet weather can often serve to exacerbate sewage runoff problems and spread odor. The monthslong streak of silence from the noses of residents was broken, presumably from the heavy rains, and five complaints were registered last month, according to Fore.

Yet while the floods may have triggered an increase in the odor complaints, the reservoir’s presence could have helped to avert heavy damage in the area.

“This reservoir was designed to minimize overbank flooding on the Thorn Creek and to intercept combined sewage overflows; the captured sewage is properly cleaned and disinfected before it is released into the environment,” Fore said.

Beckman says his office used to receive numerous complaints about odor when the reservoir first came online. Now the village redirects the community’s qualms to MWRD.

Beckman says some residents have said they stopped complaining, despite the odor being so overwhelming it sometimes prevents them from being outside.

“When they started complaining two to three years ago about it, it just didn’t seem like things were getting done so they just gave up,” Beckman said, reflecting on a recent conversation with one resident.

In a written response, Fore said MWRD has been committed since the groundbreaking of the reservoir to ensure that the smell is reduced each year.

“No, the MWRD was not slow when addressing this issue,” she said. “After installation of the infrastructure as well as some operational changes, there was a significant decline in odor complaints — from 174 odor complaints in 2016 to fewer than 10 annually in 2020, 2021 and 2022.”

Beckman said he believes there was a lack of action for many years, so “there are people who experience odors that just don’t call anymore.” But regardless of whether the decrease is because of tangible action from MWRD or a response to inaction by the water district, the future investments clarify the group’s mission to reduce the nuisance.

“I am hoping MWRD continues with their commitment to provide odor reducing measures and we’ll just have to wait and see if they work,” Beckman said.