Wastewater plant CMAR shows artificial influent increase after sampling relocation; staff working with DNR
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Summary
City staff told the committee that a sample-point change tied to headworks screening equipment caused an apparent increase in influent loading on the 2024 CMAR; staff said the increase is artificial and they are working with the Department of Natural Resources to resolve reporting.
The Finance and Personnel Committee received the 2024 Compliance Maintenance Annual Report (CMAR) for the Isle La Plume wastewater treatment facility and voted to accept the report unanimously on June 5.
Assistant Superintendent Brian Hine told the committee that a plant upgrade installing new headworks screening equipment required relocating the composite influent sampler to a point that records higher biochemical oxygen demand (BOD) and total suspended solids (TSS) than the previous location. Hine said the downstream primary sampler remained consistent and the screening equipment appears to remove a substantial portion of the loading captured by the relocated sampler, creating an artificially elevated reading in the CMAR.
Hine said staff expected the change and had discussed the issue with the DNR; a meeting with the basin engineer occurred the same day as the committee meeting. He told members the apparent deficiency in influent flow and loading is not reflective of the plant’s treatment performance and that staff are working with the DNR to resolve the reporting designation.
Committee members asked about maintenance ratings (the facility graded itself lower than some members expected) and the possibility of an energy-efficiency study. Staff said much of the equipment is newer from recent upgrades, that conditioning and optimization of systems remain ongoing, and that some energy and process reviews will await having all systems online and operational for a period of reliable data. Director Gallagher estimated some related energy/exchange steps with Xcel Energy could require an 18-month process and suggested 2026 as a target for certain energy initiatives.
Council members commended plant staff and noted high overall ratings in the CMAR; the committee unanimously approved the CMAR resolution (moved by Council member Newberry, seconded by Council member Northwood).
Staff said they would continue to work with the DNR on sampler designation and follow up on energy-efficiency opportunities as the upgraded systems run longer and provide more operational data.