Midway residents have been making a stink about a sulphurous smell for years.
The suspected source is the sewer facility just outside city limits south of state Route 113, where wastewater sits in ponds for treatment. The smell, residents allege in lawsuits, has wrought health problems.
Complaints prompted the Utah Department of Health and Human services to begin looking for evidence of a health issue in 2024.
July 9, state health officials told the Heber Valley Special Service District, which operates the ponds, the study didn’t find the public was at risk.
DHHS toxicologist Alejandra Maldonado said she and her colleagues focused solely on hydrogen sulfide.
“We don't see any apparent public health hazard from hydrogen sulfide exposure. However, some levels may exceed the lowest odor threshold,” Maldonado told wastewater officials. “Essentially, people may be smelling it.”
Hydrogen sulfide is known for its rotten egg aroma, and it can cause symptoms like headaches, fatigue and respiratory problems. But may not pose an issue in acute, low doses — hydrogen sulfide is found in everything from volcanoes to flatulence.
DHHS tests also detected the toxin at the Midway ponds. Click here to review the researchers' slide deck, which includes some of their data.
In 2025, researchers set up four hydrogen sulfide monitors in the spring and summer — the times of year when residents have most commonly reported an odor.
The monitor located at the wastewater ponds was the most sensitive and took readings more frequently than those in the surrounding neighborhoods. But the cassette-based monitor ran out of tape during May 2025, so there’s a gap in the data.
Still, it found that the concentration of hydrogen sulfide above the ponds sometimes exceeded healthy levels, particularly in June.
The neighborhood monitors, which never stopped recording, never detected unhealthy levels. Only two of the three ever detected any hydrogen sulfide.
Resident complaints have tended to peak in April or May, leading some on the wastewater district board to wonder if there are other smelly things in the air, like the odor of Bradford pear trees.
According to DHHS risk assessor Gilbert Castaneda, that’s possible — the state study only looked at the one compound, hydrogen sulfide, since it can be toxic.
“In the springtime, when everything starts thawing, bacteria everywhere in the soil starts up eating organic matter, that can also release some sulfur compounds,” Castaneda said.
It’s not clear whether the state will conduct additional studies.
The lawsuit filed by residents who say they’ve suffered “syndrome of the sewer worker” remains pending.
A 4th District judge ruled in May that residents can only sue over issues from December 2023 or later, since they didn’t formally complain to the wastewater district until December 2024.
The Heber Valley Special Service District has denied it intentionally harmed residents. Another court hearing has not yet been scheduled.
Maldonado said she’ll provide city and wastewater officials with a short, digestible summary of the study’s findings to distribute to residents.
She also plans to return to the Heber and Midway area to present the findings in a community meeting later in the summer or early fall.
