Sedona council reviews wastewater facility plan, orders soil study and utility talks

Sedona City Council on a lengthy agenda item reviewed a final Wastewater Reclamation Plant facility plan that models plant capacity, compares PFAS-removal technologies and ranks options for effluent management including additional recharge wells, delivering reclaimed water to parks and schools, and full advanced water purification (AWP) for potable reuse.

The plan, presented by Roxanne Holland, director, summarized a hydraulic and concentration-capacity analysis, tested two PFAS-treatment approaches — granulated activated carbon (GAC) and ion exchange — and scored five combined effluent-management alternatives. Holland told the council she has programmed conceptual PFAS costs into the city’s 10-year capital improvement plan and recommended further sampling and targeted pilot testing before any large-scale construction decisions.

Why it matters: the choices affect long-term water supply, wastewater rates, nearby land use at the Dells and Sedona’s role in regional water planning. The council’s direction will determine what the upcoming wastewater rate study models, what capital projects are advanced in the CIP and which partnerships the city pursues with Arizona Water Company and other utilities.

Key findings and figures from the facility plan - Capacity: City modeling shows the plant currently meets build-out hydraulic capacity for most processes; staff identified a bottleneck at the tertiary filters to the current UV system and have already included a UV replacement change order of $386,000 in the FY26 CIP to increase redundancy. - Waste strength: comparing 2012–2016 to 2022–2024 data, the plant recorded increases in several load parameters: flow +4%; chemical oxygen demand (COD) +9%; total suspended solids (TSS) +13%; volatile suspended solids +12%; ammonia/nitrate +24%. - PFAS testing: limited sampling showed PFOA levels exceeding recently adopted drinking-water maximum contaminant levels (MCLs) in some samples; staff noted that effluent concentrations can exceed influent concentrations at wastewater plants and recommended continued, budgeted sampling to establish a robust baseline.

PFAS treatment alternatives (planning-level costs and trade-offs) - Technologies evaluated: GAC and ion exchange, each sized for current flow (~1.3 MGD) and build-out (~1.8 MGD). Both are established in pilot work for PFAS removal; GAC requires larger footprint and more frequent media replacement but lower power; ion exchange has smaller footprint and greater flexibility but requires more robust hazardous-materials handling for spent media. - Cost ranges: conceptual capital for PFAS treatment was presented in a planning range of roughly $28.3 million to $34.4 million; annual O&M roughly $600,000–$900,000. The firm-level estimates include a 30% contingency and have an acknowledged accuracy band of about +/-50% at this planning stage.

Effluent-management alternatives and scoring - Reclaimed-water delivery to parks and schools (phased): Phase 1 to the high school (short new pipe; much existing pipeline is in place but requires condition assessment/rehab), Phase 2 to Sunset Park, and Phase 3 to other parks and West Sedona School. Conceptual capital ranged from about $14.5 million (limited phase) up to $28.6 million for broader distribution. O&M estimates ranged ~$200,000–$400,000/year; per-thousand-gallon cost estimates fell between about $13.13 and $16.10, with cost-per-unit declining as distribution expands. - Advanced water purification (AWP) / direct potable reuse: three sizing scenarios were studied (0.9, 1.3, 1.8 MGD). Conceptual capital ranged roughly $132.2 million to $161.1 million; estimated annual O&M $2.8 million–$4.5 million. Holland said ADEQ finalized AWP rules in March but permitting would require pilot testing and a year of water-quality sampling, so the permitting and construction timeline is multi-year. - Recharge-well strategy (2013 optimization plan updated): staff reviewed the 2013 plan that assumed abandoning up to 200 acres of irrigation at the Dells, retaining about 27 acres of wetlands, and building up to six recharge wells for build out (two already constructed in 2017). Council discussion noted prior high-level cost estimates for wells in the neighborhood of about $5 million per well (planning-level and subject to change) and that the number of wells required depends on actual well performance.

How the alternatives scored: using a multi-criteria weighting process with five internal and consultant evaluators, the top-ranked alternatives were: (1) abandon 200 acres of irrigation and add recharge wells (the 2013 plan update), (2) abandon irrigation, add recharge wells and deliver reclaimed water to parks and schools, and (3) abandon irrigation and implement AWP. Maintaining the status quo with only additional recharge wells scored lowest in that ranking.

Council discussion and direction Councilors pressed for clarity on costs, timing and who benefits from recharge (several members asked whether recharge primarily benefits downstream users). City staff and Arizona Water Company representatives said regional partnerships would be important because reclaimed or AWP water could count toward local supply, and Arizona Water Company’s planning assumes eventual reuse of the city’s effluent as part of a diverse supply strategy.

After discussion, the council gave staff direction — by general consensus rather than a recorded roll-call vote — to: 1) commission a focused geotechnical/soil-sampling and analysis scope at the Dells to determine whether historic irrigation would require remediation or mitigation before development (staff estimated the initial investigative scope at under $10,000 and suggested a three-month turnaround if contracted promptly); and 2) pursue defined partnership conversations with Arizona Water Company and invite Oak Creek Water Company to engage, so the city and potential partners can develop cost-sharing concepts and scenarios the rate study should model. Council asked that staff return with results and refined options in time to inform the upcoming wastewater rate study and the 10-year CIP (staff requested guidance that would allow inclusion in the rate-study modeling by year-end).

PFAS and the rate/CIP context - PFAS compliance: staff said ADEQ has opened a docket for PFAS rulemaking for wastewater and that a formal rule could take roughly two years; compliance schedules could follow. The presentation assumed wastewater limits might mirror the current drinking-water MCLs for planning. Holland said she has already placed PFAS capital and O&M planning-level numbers into the city’s 10-year CIP and into assumptions for the forthcoming rate study. Councilors repeatedly noted uncertainty about timing and potential grant funding and weighed whether the city should “get ahead” of regulations or wait for a mandate.

Next steps and timeline mentioned in the meeting - Staff will scope and, if authorized administratively, contract for the Dells soil/geotechnical sampling and an advisory memo on potential remediation needs (estimated initial cost under $10,000; three-month sample-to-report target if procured quickly). - Staff will open partnership discussions with Arizona Water Company and invite Oak Creek Water Company to join regional planning conversations; staff will also bring planning-level partnership concepts back to council to inform rate-study assumptions. - Staff will continue PFAS sampling and pilot recommendations; PFAS planning-level costs already are reflected in the CIP.

Quotes from the meeting - “We have already conducted some PFAS testing on our both our influent, our effluent, and some of our POC wells,” Roxanne Holland said, noting the results “do show we are exceeding PFOA.” - “We need to partner with or further partner with Arizona Water Company,” Holland told the council on regional coordination; Arizona Water Company representatives said they view Sedona effluent as a legitimate long-term water supply and urged the city not to close off options.

Ending The council did not take a formal, recorded vote on a single alternate path during the meeting. Instead it directed staff by consensus to proceed with targeted soil sampling and to pursue utility partnership discussions, with the intent that staff return with results and recommended language and cost scenarios the council can use to finalize direction and to include in the rate study and 10-year CIP.