Riverbank council hears feasibility options for wastewater plant; study recommended

Riverbank Vice Mayor Cindy Fosse urged the City Council on June 24 to commission a feasibility study to evaluate how best to address capacity, permit and long-term costs for the Riverbank Wastewater Treatment Plant.

The study would compare three broad options: complete the city’s planned recycled-water upgrade at the existing plant; construct pump stations and a pipeline to send some or all wastewater to the City of Modesto’s treatment system (regionalization); or redesign the local plant and pursue a surface-water discharge permit to the Tuolumne River. Fosse told the council the feasibility work would likely cost about $50,000 to $75,000 and could include potential cost-sharing by Modesto.

Why it matters: the city has been working on a major upgrade after state regulators raised concerns about groundwater impacts and treatment capacity. Council members and residents said the projected price increases and loan package for the recycled-water project are creating significant rate pressure for households. A feasibility study, proponents said, would give the council better fiscal and technical comparisons before committing to a multi-decade capital plan.

Fosse summarized the three options. She said the recycled-water project — which staff and consultants have been designing and which has an approved state loan application — is now estimated in the meeting transcript at about $124 million and that the city has an approved state loan in the range discussed at the meeting (an $85 million SRF loan was referenced); grant funding for recycled water of roughly $15 million was also discussed as part of project financing. The recycled-water approach would provide additional seasonal capacity by supplying treated water for irrigation during summer months, the vice mayor said.

Public Works Director Cody Bridgewater responded to technical questions. He said discharge to the Stanislaus River would require a National Pollutant Discharge Elimination System (NPDES) permit and a much broader constituent testing program (the council heard that roughly 160 constituents could be evaluated under that federal permitting process). Neil Colwell, the city’s consultant on regulatory matters, explained that the Central Valley Water Board requires a feasibility demonstration if a new discharge to surface water is proposed, and that many of the advanced treatment components (biological nutrient removal, filtration, disinfection, biosolids handling) would still be required for a surface-water permit — meaning that a surface-water discharge is not necessarily a lower-cost alternative.

Supporters of a study noted uncertainty in construction and financing: council members and speakers pointed out construction cost escalation over the past decade, the potential loss of previously identified grant funding if the project scope changes, and the city’s existing investment in design work (roughly $6 million of design expense was discussed in the public record). Several council members said they want precise cost estimates for pipeline routing, lift stations, easements and connection fees before deciding on a final path.

Residents and other speakers urged caution. Written and oral comments from multiple District 1 residents said a large rate increase (the city’s rate study projects monthly sewer bills that would rise substantially by 2027 under the current plan) would be difficult for many households. Speakers emphasized protecting farmland, local groundwater, and the city’s fiscal capacity.

Council direction and next steps: the council did not take a final vote on a capital project at the meeting. Several members signaled support for pursuing a formal feasibility study to quantify: pipeline and lift-station costs for regionalization; the cost to upgrade the city plant to meet current and future permit requirements if the recycled component were reduced or removed; and the implications for ratepayers. Staff said the study could be procured by competitive bid; Modesto might contribute toward study costs, staff added, if regionalization options were pursued. The council also emphasized continued pursuit of grants.

The meeting record shows robust public comment, multiple technical questions for staff and consultants, and no formal change to the city’s currently approved 60% design effort. The vice mayor and staff said value-engineering work between the 60% and 90% design milestone is the right time to seek cost reductions and to sharpen project scope.

Ending: The council left the item open for further analysis and directed staff to return with a scope and cost estimate for a feasibility study. A joint council/planning meeting about Riverwalk and other items was scheduled for July 9; the council also noted it will continue outreach and pursue available state grant opportunities.