Flagstaff to study new wastewater plant as solids loads, growth outpace existing facilities
Loading...
Summary
City water leaders told council the two existing plants are nearing solids-processing limits despite conservation-driven lower liquid flows. Staff presented a cost estimate and phased options; council asked staff to pursue funding research and keep the project in the 10-year CIP.
City water staff told the Flagstaff City Council Friday that the city’s two wastewater treatment plants — Wildcat Hill and Rio de Flag — are approaching their solids-processing limits even though per-capita water use has fallen, and that a new treatment plant will be required to serve projected growth.
Lee Williams, Director of Water Services, said conservation has reduced the liquid flow to the plants but has not reduced the solids load, because modern fixtures use less water but the same amount of waste is produced. “We are not near the liquid capacity, but we are at the solids capacity,” Williams said, noting that solids-processing constraints — not liquid capacity — drive the need for new treatment.
Cost and options: Williams presented a current construction cost range of $25–$30 per gallon of capacity. A 10-million-gallon-per-day plant at that unit price would cost about $250–$300 million in today’s dollars; a 14-MGD plant to serve buildout would be in the $350–$428 million range under current assumptions. Staff described two approaches: build a single new plant to replace the existing Wildcat facility, or construct the new facility in phased 2.5-MGD segments using membrane bioreactor (MBR) technology or conventional treatment. MBRs produce very high-quality effluent and can be well suited to future advanced-water-treatment goals.
Funding and schedule: The Rio/Wildcat design is programmed in the 10-year CIP; the city placed a design allocation (roughly $25 million) in the plan. Williams said Flagstaff is on a list for Water Resources Development Act (WRDA/WERDA) grant consideration and that an approximately $5 million federal design allocation was identified but has not yet been funded. Staff told council they will research combinations of rate revenue, low-interest loans, state and federal grants, development-impact fees and voter-authorized bonds to fund construction, and that rate revenues alone would not cover the full construction cost.
Council direction: Members asked staff to continue the CIP design work and to explore phased technical options, grant opportunities and financing structures. Several councilors said the city should be aggressive in seeking federal and state grants and should study phased construction to reduce immediate sticker shock while protecting long-term capacity.
Ending: No decision to build was made Friday; staff will continue design-level work already in the CIP and return with more refined cost estimates and funding scenarios.
