Tulare staff and consultants recommend new oxidation-ditch wastewater plant as costs top $100 million
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Summary
City staff and consultants told the Tulare City Council the town’s domestic wastewater plant is aging and effectively limited to about 4 million gallons per day; consultants recommended a new parallel “greenfield” plant using an oxidation ditch process with estimated costs between $100 million and $160 million, and lifecycle costs of roughly $163M–$184M.
A city presentation on March 3 showed Tulare’s domestic wastewater treatment plant is near the end of its useful life and faces capacity limits because wastewater concentrations have risen even as flows fell. The city received a draft facility plan from consultants Corolla Engineers recommending construction of a new parallel wastewater plant using an oxidation ditch process.
The draft report, presented by Tricia Winfield and principal consultant Ryan Selman, said the original plant — much of it built in 1974 and expanded in 1996 — was designed for a higher flow but now treats higher pollutant loads that reduce effective capacity. “With the loadings we are seeing today, the plant’s capacity is closer to 4 MGD, not 6 MGD,” Selman said, noting winter performance and storm events can further reduce treatment capability.
The consultants outlined three viable approaches and recommended a greenfield solution sited beside the existing plant. John Witter, Corolla’s project manager, described advantages of an oxidation ditch: “It’s simpler to operate, less susceptible to upsets from wet weather and provides larger basin volume to attenuate influent variability,” he said. The team said membrane systems and intensified biological processes were considered but carry higher recurring O&M costs.
Cost estimates are preliminary planning-level figures: common improvements and site work plus treatment components put a full-build capital range in the roughly $100 million to $160 million band; a 20-year lifecycle cost projection ranged about $163 million (for the MLE-style bioreactor scenario) up to $184 million (for a membrane bioreactor). The consultants emphasized contingency ranges and noted differences between the technology options fall within the estimate margin of error.
The report recommends next steps including finalizing the facilities plan, conducting preliminary design, pursuing a sewer and water rate study to assess revenue capacity, and advancing a funding strategy (the city and BPU are considering bonded financing). Winfield told the council that the Board of Public Utilities will adopt the final study at a future meeting and that the city is likely to bond the work and service debt with rates.
Council members pressed on phasing, salvage of existing assets, and potential cost savings from refinancing bonds. Staff noted phasing could reduce initial cash needs but would require operating two processes in parallel during construction and add operational complexity. The consultants also said some existing solids‑handling infrastructure might be rehabilitated to reduce capital outlay; they estimated such reuse could shave tens of millions from the projected maximum.
The council received the draft facility plan and instructed staff to continue coordination with the Board of Public Utilities and the city’s rate consultant. No formal design or funding decision was made at the March 3 meeting; the BPU and council will consider those actions in coming months.