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Arcata staff present sea-level rise options for wastewater plant; levee protection and full relocation cost very different
Summary
City engineers and consultants presented a long-range feasibility study that ranks levee-augmentation (protect) and full relocation (retreat) as leading options for Arcata’s wastewater treatment facility, with estimated capital costs ranging from roughly $30 million (levee approach) to about $200 million for relocation.
Arcata city engineer Netra Khatri and GHD technical director Rebecca Crow told the City Council on Jan. 21 that the city’s wastewater treatment facility long-range feasibility study evaluates how to keep the plant safe, compliant and operable as sea levels rise.
“This project was to evaluate strategies to protect, relocate or otherwise adapt the city’s wastewater facilities to maintain safety, regulatory compliance and prepare for future sea level rise,” Rebecca Crow said during the presentation, which staff said was funded by a State Water Resources Control Board grant administered through the Rural Community Assistance Corporation.
The study analyzes coastal-hazard risks at the existing facility, develops top-ranked alternatives, and provides cost and funding information to inform later council decisions. Crow said the city’s Phase 1 improvements are about 98.5% complete and that the feasibility study purposely does not select a final alternative but narrows options for council consideration.
Consultants identified two leading treatment-system strategies: a levee-augmentation protection alternative and a full relocation of the treatment plant. Crow summarized the capital-cost differences presented to the council: levee-augmentation and protection measures were characterized in the approximately $30,000,000 range, while relocating the facility—including land acquisition, permitting and new infrastructure—was described as “more in the $200,000,000 range.” She also noted relocation would add ongoing operational costs tied to pumping and energy for moving effluent to a new site.
The study evaluated disposal and discharge alternatives as well. Options ranged from levee maintenance and enhancement-marsh protection (Cit y staff referred to cost bands such as roughly $4–$10 million for certain levee maintenance scenarios) to larger new enhancement projects (presenters cited a wide cost range around tens of millions of dollars) and a potential Redwood Marine Terminal ocean outfall (preliminary estimates in the $60–$130 million range). Consultants described trade-offs between preserving the ecological and recreational benefits of the marshes and long-term resilience.
Consultants said they considered but did not further develop some alternatives, including consolidation with neighboring systems and decentralized on-site treatment, because those options did not show high-value synergies or standalone feasibility under current conditions.
Netra Khatri said the study included outreach with neighboring special districts and regulators and two public meetings (in 2024 and 2025). Staff will bring a refined recommendation and options back to the council in late March or early April and sought public feedback in the meantime; presentation slides will be posted on the city website.
The council thanked staff for the extensive work and asked for more data and local-focused briefings on enhancement-marsh strategies and potential relocation sites. No formal council direction or vote on a preferred alternative was taken at the meeting; staff said they will return for direction once the draft feasibility work is finalized.
