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Rigby council tables $5M–$8.1M headworks upgrade as staff pursues grants
Summary
The council paused a decision on major upgrades to the city wastewater plant’s headworks after staff outlined two options — a $5 million headworks expansion or an $8.1 million plan including upstream equalization — and recommended exploring grants and budget planning before committing reserves.
Wastewater Treatment Plant Supervisor Scott Humpherys told the Rigby City Council on April 16 that the plant’s headworks cannot reliably handle combined peak flows when both town lift stations and the onsite process-water lift station operate simultaneously, allowing debris to bypass screens. He warned that if average daily flow reaches 2.59 million gallons per day for two consecutive months the Idaho Department of Environmental Quality will require the city to submit an upgrade plan.
Humpherys summarized recent flow data: the city’s 2022 average was about 560,000 gallons per day, last year averaged about 890,000 gpd, and current flows — when combined with recycled process water not captured by the inflow meter — are approaching regulatory thresholds. He said an outside source (Bob Evans) contributes an estimated 350,000–500,000 gpd to the system and that continued growth could push totals higher.
Staff presented two alternatives: a headworks expansion only (wider channels, additional or larger screens, building expansion and a redundant grit separator), estimated at about $5 million; and a combined upstream equalization and headworks expansion (equalization basins, a metered onsite lift station and building expansion), estimated at about $8.1 million. Humpherys said the city could potentially fund some or all of the work from existing reserves and the annual depreciation allocation (about $1 million per year) without raising rates, but emphasized that grant funding (for example, DEQ annual grants or USDA Rural Development programs) would reduce the draw on reserves and is not guaranteed.
Council members pressed staff to pursue outside funding and to provide wastewater budget adjustments with clearer cost and funding scenarios. Councilman Timothy Howe moved to table the item to allow staff time to explore grant options and prepare related budget items prior to October; Councilwoman Melanie Allen seconded, and the motion carried unanimously.
The action postpones any commitment of city reserves and asks staff to return with grant findings, revised project scopes and budget proposals. No formal project authorization or procurement action was taken at the meeting.
