Mona City approves $5,500 sewer impact fee, funds plant upgrades after master plan finds pipe capacity but manhole infiltration

Mona City Council on Oct. 14 approved a $5,500 sewer impact fee per equivalent residential connection and authorized purchases to repair and update equipment at the city sewer plant after hearing a sewer master plan that found collection pipes largely have 20 years of capacity but that infiltration at manholes is increasing treatment costs.

The council’s action followed a presentation from Dan, the consulting engineer who led the sewer master plan, and an impact-fee analysis from Coheed Dieter of Energy Finance and Government Consulting. The master plan used the state’s flow-assumption protocol of 100 gallons per capita per day for modeling and reviewed existing meter data and plant records to set a conservative baseline.

Dan told the council that measured flows into the treatment plant average about 100,000 gallons per day and that, using the city population, that equates to roughly 56 gallons per capita per day for metered influent; tank data showed higher numbers in some locations. "When we look at the numbers coming into the sewer treatment plant, there was about a 100,000 gallons per day," he said. Using a 100-gallons-per-capita assumption for planning gave the consultants a conservative basis for the 20-year projections.

The engineering maps shared with the council show the city’s sewer network by pipe size (8-inch up to a 15-inch trunk line) and indicate that most pipes have substantial unused capacity under the projection scenario. The consultant said only the line on 200 West (from 700 South to 300 South) showed the greatest strain, but even that segment would still have capacity equivalent to roughly 100 additional single-family homes under the model used.

The report’s primary operational concern was infiltration and inflow concentrated in the lower area near the plant and lift station. Dan described repeated nighttime manhole inspections, flow-metering runs, and review of video inspections. "As the groundwater comes up, it's just putting pressure on those pipes from the outside. It's just pushing in," he said, pointing to specific manholes numbered in the report. The engineer identified manholes 18, 6 and 5 as having the worst infiltration and noted that sealing the outside of manholes and raising manhole covers had reduced inflow at some locations.

The consultants presented remediation options with estimated costs: full pipe replacement with PVC or HDPE, pipe relining (the most expensive), or targeted manhole repairs such as epoxy lining and external sealing. The consultant recommended prioritizing manhole sealing and targeted repairs as a less intrusive, lower-cost first step to reduce I&I and lower treatment costs.

Coheed Dieter summarized the impact-fee calculation, telling the council that the city’s recent collection-and-treatment project and related sewer work totalled about $18.8 million, of which roughly $9 million was grant funding and therefore excluded from the fee calculation. After excluding grants, the net amount to be allocated to connections was about $9.5 million. "When you divide the 9,500,000.0 by the total connections, it's $6,454. That is the maximum impact fee that you could charge," Dieter said, adding that the council may charge less than the statutory maximum.

Dieter explained the number of equivalent residential connections (ERCs) used: approximately 1,479 total ERCs served and roughly 885 counted as future growth in the model. He also noted that multifamily residential units and commercial customers can be charged proportionally using meter-size or measured flow if appropriate.

Council members debated where to set the fee below the statutory maximum. Several council members said $6,000-plus felt high for builders and new homeowners; others, including a public commenter, urged a higher fee to help retire debt and cover ongoing maintenance. Resident Josh Davis, who spoke during the public hearing, said the city should consider whether the planned new connections and any commercial customers would cover debt-service needs and suggested the council "think about raising it a little bit more" given the city’s outstanding loan obligations.

After public comment the council closed the hearing and voted to set the impact fee at $5,500 per ERC. The council was informed that, per the ordinance-adoption process discussed by the consultant, an adopted ordinance will take 90 days to go into effect to prevent surprise charges for projects already in the permitting pipeline.

Separately but related to sewer operations, the council approved two capital expenditures to keep the plant operating: $130,000 for sewer drum screens and a controller to restore or improve solids handling, and $30,000 to replace the sewer-plant fire alarm system. Council discussion on those items noted that a larger original plan for drum-screen replacement exceeded $300,000 and that reusing existing components plus targeted parts purchases would save the city substantial cost.

Council members and staff stressed that taking action to control infiltration and to maintain plant equipment are complementary measures: reducing I&I lowers treatment volume and operating cost, while upgraded plant equipment and alarms reduce emergency responses and asset risk. The consultants and staff also pointed out that most of the collection system consists of relatively new PVC pipe and, aside from localized infiltration, does not require systemwide replacement in the 20-year horizon.

The council directed staff to: finalize the ordinance language implementing the $5,500 impact fee, file the required public-notice and ordinance-adoption paperwork, and schedule implementation steps consistent with the 90-day effective period; and to pursue prioritized manhole and targeted repair work and the approved plant equipment purchases.

The council’s actions do not commit the city to comprehensive pipe replacement; instead, the emphasis is on managing infiltration and maintaining plant reliability while using the impact fee revenue to recover eligible system costs and support future connections and maintenance.

The ordinance implementing the fee and the formal contracts for the plant purchases will appear on a future agenda for final paperwork and administrative follow-up.