Casa Grande details $104 million Phase 4 wastewater expansion to keep up with development

Casa Grande city staff and consultants with Wilson and Company on Wednesday outlined a two-part expansion of the city’s Water Reclamation Facility that city officials say is needed to keep up with industrial and residential growth and to resolve an ongoing permit-capacity mismatch.

Brian McBride, national lead for water and wastewater at Wilson and Company, said the city is already handling higher flows than its 2022 effluent permit allowed and that Phase 4 was split into a faster, lower-cost Phase 4A that is under construction and a larger Phase 4B planned to follow. "The plant was first commissioned in the 1970s" and has undergone prior upgrades, McBride said, noting Phase 3 was commissioned in 2012.

The split was driven by urgency and funding, McBride told the council. Phase 4A uses an accelerated schedule and targeted, lower-cost interventions — including converting an abandoned pretreatment basin into an equalization basin and retrofitting biological treatment with a suspended fixed‑film system — so the plant could meet updated permit conditions sooner and postpone some larger expenditures until funding is in place.

McBride said Phase 4A included upgraded headworks, a new junction box for incoming force mains, an upgraded influent pump station (to 36 million gallons per day hydraulic capacity before the equalization basin), a receiving station for septage, and an F1 pump station to support reclaimed-water reuse and recharge. He said permit amendments allow an 18 million gallons per day permitted capacity and "unlimited discharge" under the new permit language for effluent disposal.

Costs listed by McBride for Phase 4A were approximately $34,000,000. He estimated Phase 4B at about $70,000,000, bringing the combined Phase 4A/4B program to roughly $104,000,000. McBride also said Phase 4B would be a roughly 30‑month project once design and procurement are complete, with a planned construction start in the second quarter of 2026 and substantial completion targeted for the fourth quarter of 2027.

City staff said the approach reduces near-term permit risk and spreads capital needs across budget cycles. "Breaking that down into what I consider to be bite sized components for us to be able to put a financing plan behind that became key to the strategy that we started with Phase 4A," a city staff member said during the presentation.

Councilmember Anthony noted earlier public cost estimates of about $80 million and asked for clarification. A city staff member replied that the earlier $80 million number combined several related projects — the Phase 4A plant work, the Courtson force main line already being installed, a west-side reuse pipeline and a west-side lift station — and that the current $104 million total reflects the Phase 4A/4B plant work specifically plus the additional pieces of the broader program.

Consultants said the equalization basin conversion plus a suspended fixed‑film biological retrofit were chosen because they increase treatment capacity while avoiding very expensive new concrete basins. McBride said the fixed‑film retrofit increases the biological treatment capacity by roughly 50 percent where applied and limits the need for new large basins.

Wilson and Company and the city said a construction manager‑at‑risk procurement (PCL is the CMAR on Phase 4A) allowed overlapping design and construction and helped meet the accelerated Phase 4A schedule. McBride told the council the 4A work is nearly complete and within months of finishing the first deliverable.

City staff and consultants also described operational reasons for Phase 4B: converting the equalization basin to emergency storage, expanding peak‑hour capacity for downstream processes, improving operator safety, expanding laboratory and parts storage, and enhancing odor control. McBride said cleaning up abandoned, undocumented equipment left in place by past upgrades is another key 4B objective to reduce future construction uncertainty and operations risk.

On funding and grants, staff said the city applied for a Bureau of Reclamation Smart Water Program grant for a recharge site and was denied in an initial round; staff said they are reapplying after meeting with the funding agency and remain confident. McBride and staff stressed that delays in Phase 4B would raise operational risk, increase per‑gallon operating costs and the likelihood of permit or odor issues as influent flows grow.

The presentation closed with council questions on modeling and projected horizon for the expanded capacity; McBride said the modeling the team reviewed projected roughly seven years of additional capacity under expected growth patterns before further major new capacity would be required. City staff noted the plant site has acreage for future expansion and that other long‑term options exist, including east‑side and west‑side partnerships, but that service needs will require more capacity as the community develops.

No formal council action was taken during the study session; the presentation was for policy and budget planning ahead of upcoming capital and operating budget decisions.