GUNNISON—Gunnison City Council approved a temporary treatment plan for its wastewater lagoon system April 15 after operators reported reduced performance and growing operational concerns in one of the city’s treatment cells.

Council members moved the sewer lagoons item to the start of the meeting to allow the presenter to speak before leaving for another commitment.

Garrick Willden, from Jones & DeMille Engineering, told the council the city has taken cell No. 1 offline and is in the process of drying it out after sludge buildup created unsafe conditions.

“There was so much sludge they were worried they could get back in and out,” he said, describing an incident where workers became stuck in the lagoon.

With cell No. 1 out of service, all wastewater is currently being routed into cell No. 2. That shift has reduced the system’s ability to properly treat waste because the second cell has less surface area, limiting oxygen transfer needed for biological treatment.

“What you need for sewer loading to function properly is oxygen,” Willden said. “Right now, we really don’t have enough surface area and mixing, and so the solids aren’t being processed as they should.”

He said the lack of oxygen has led to anaerobic conditions, allowing bacteria to continue breaking down material but producing hydrogen sulfide gas, which carries a noticeable odor.

“We can start to smell (hydrogen sulfide), and we can see the sludge building up, so we know it’s a problem,” he said.

To stabilize the system, the city approved the use of an oxygen-enhancing treatment provided by Wastewater Innovations. The treatment involves injecting an oxygen-rich salt solution designed to increase bacterial activity and improve processing of solids.

The cost includes a $4,000 installation and initial treatment, followed by $4,000 per month. An additional $1,000 per month could be required if higher dosing is needed after the first month.

Council members discussed the timeline and agreed the treatment would likely be needed for three to four months while the city works to clean out cell No. 1 and return it to service.

Willden said the first month of treatment would help determine how effective the approach is and whether adjustments are needed.
Council members also raised concerns about long-term system performance and whether similar issues could develop again without structural changes.

According to Willden, cell No. 1 has not been cleaned out for decades but, after drying, appears to contain only a few inches of actual solid sludge.

“It’s amazing what bacteria does with just some sunlight and some oxygen,” he said, noting that most of the accumulated material had broken down over time.

City staff said they plan to measure the total sludge volume by drying and stockpiling a test section to determine whether city crews can handle removal or if a larger contracted project will be required.

The city has also placed a wastewater study on its capital improvement list and plans to pursue funding through the Community Impact Board. Officials said the study could be available for application around June and would likely evaluate options for expanding or reconfiguring the lagoon system.

Potential changes could include increasing the surface area of the primary cell or adjusting how wastewater flows through the system to improve treatment efficiency.

Council members said any long-term solution would be guided by the study’s findings.

The council approved the temporary treatment plan unanimously and directed staff to bring the issue back in three months for review.
City officials said funding for sewer-related issues had already been included in the current year’s budget, which set aside about $100,000 for that purpose.