MOUNT VERNON — City officials expect to remove the remaining lime sludge from temporary storage by the end of the year, capping off a four-year removal effort.
Safety-Service Director Tanner Salyers estimates about 12,100 tons remain at the temporary storage site adjacent to the water treatment plant at 1550 Old Delaware Road.
“Depending on external factors … like weather, site availability, and the big one being contractor availability, we are on pace to have all material removed from the temporary site by the end of fall 2026,” he told city council members on Tuesday.
“In 2025 we successfully removed about 10,384 tons, achieving key interim milestones set by the EPA. Since 2022, the removal has exceeded about a little over 42,000 tons.”
Salyers said removal efforts cost approximately $125,000 per year, with trucks hauling the sludge.
Sludge removal
The city has removed 42,078 tons of lime sludge from its temporary storage site on Old Delaware Road over the past five years. Here’s the annual breakdown:
•2022: 12,745 tons
•2023: 11,900 tons and
•2024: 7,040 tons and
•2025: 10,384 tons
The city contracted with Kokosing Industrial in April 2022 to remove the sludge in its west lagoon to the temporary storage site.
Mayor Matt Starr said at the time that the west lagoon was full, and the east lagoon was filling up rapidly. There was concern that a submerged pipe that moves sludge into the lagoon could clog up, in which case the city would have to shut down the water plant.
In September 2022, the Ohio Environmental Protection Agency ordered the city to remove the sludge from the temporary storage site. The OEPA set a Dec. 15, 2023, deadline for removal.
The OEPA granted the city’s appeal, and the city started a phased removal.
Ongoing management of lime sludge
With removal at the temporary storage site nearing completion, city officials are turning their attention to ongoing sludge management.
The sludge goes to two storage lagoons across the road from the treatment plant.
Salyers said the city has accumulated a significant backlog at the site. He estimates it at roughly 72,000 tons.
“In the past, mismanagement stemmed from inconsistent annual removals and the absence of a dedicated Drinking Water Material Management plan, leading to overflows, excessive accumulation, and eventual EPA involvement,” Salyers said.
“The shortcomings resulted in higher costs and potential environmental risks from extended storage and community worries about proper handling.”
Dave Hall, water treatment plant supervisor, said the city has not cleaned out the lagoons for 40 years.
A new DWTMM plan calls for removing 120% of the lime sludge each year. That includes 2,400 tons of existing sludge and the 2,000 tons produced annually.
To do that, Salyers said an annual budget of $100,000 is essential. Future removal costs would transfer from the general fund to the water fund.
“Ultimately, this plan envisions achieving zero net accumulations by 2028 through ongoing monitoring, technological improvements to the lagoon and alignment with evolving regulations to streamline operations,” he said.
“As we grow as a community, if we start cranking out another 2,000 tons of byproduct a year, that 120% is still our target.”
Salyers said that looking ahead, the city’s focus is on expanding sustainable reuse options and bolstering local farming communities.
Salyers noted that recycling (recalcining) the lime byproduct is not cost-effective.
“Really, what we should do, whether it is by truck, by rail, we should find more farm fields,” he said. “We should find more partnerships with either other agricultural co-ops or the Ohio agricultural department and expand those options.”
What is lime’s role in drinking water?
The City of Mount Vernon started removing sludge from its west lagoon in June 2022 and hauling it to a temporary storage site next to the street department garage on Old Delaware Road. On Sept. 14, 2022, the Ohio EPA ordered the city to begin removing the lime material from the storage site.
Municipalities use lime to soften water. It helps adjust pH levels to counteract acidity and contributes to disinfection by reducing bacteria and viruses.
A byproduct of the water treatment process is lime sludge (drinking water treatment material). The sludge forms when lime binds to hard minerals, such as calcium and magnesium, and to impurities, including silica and metals.
Dave Hall, water treatment plant supervisor, said the city treats about 3 million gallons per day.
Salyers said that equates to about 2,000 tons of lime sludge.
Is lime sludge harmful?
Salyers said the primary components of lime sludge are not known to be carcinogenic, even if trace silica is present.
“When handled properly, the lime byproduct is classified as a non-hazardous waste in its dry form, although it maintains an alkaline pH between 10 and 12, which can make it dusty and potentially irritating to the skin, eyes, and respiratory system if not managed correctly,” he said.
“I want to keep highlighting that: If not managed correctly.”
However, he said that, to ensure safety, it’s essential to use protective equipment such as gloves, goggles, and respirators, along with adequate ventilation and dust-suppression measures.
Health risks include possible burns or irritation upon contact with moisture. Dust inhalation might cause coughing or throat discomfort.
The material is not flammable or explosive. While its alkaline properties could affect soil or water pH if improperly disposed of, regulated reuse minimizes environmental impact.
