State Water Board contractors outline high-level method to estimate costs and solutions for inadequate wastewater facilities and on-site systems

Contractors leading the State Water Resources Control Board's wastewater needs assessment presented a methods framework for identifying technical solutions and developing statewide cost estimates for facilities judged "inadequate" by the Board's risk analysis, and for locating opportunities to replace on-site wastewater treatment systems (OTS) through sewer connections or community cluster systems.

UCLA Laskin Center project manager Ariana Hernandez opened the meeting saying the purpose was "to present, review, and seek input on methodologies for developing and selecting solutions for inadequate wastewater facilities and on-site wastewater treatment systems, OTs, as well as assessing groundwater impacts." The team emphasized that the assessment is intended as a statewide, high-level budgeting tool and not a substitute for local engineering studies.

Maureen Koerner, research engineer with Sacramento State's Office of Water Programs (OWP), and Dr. John Johnston of Sacramento State described the method the contractor team will use to translate the list of inadequate facilities into probable solutions and unit costs. Johnston said the assessment will produce a "high level estimate of the cost. This is the 30,000-foot estimate for a statewide, for statewide budgeting, actually," and that costs will combine capital and 20-year operations-and-maintenance estimates and be converted to present value.

The team proposed four broad solution categories: repair and rehabilitation (replace worn equipment, patch collection lines), upgrades (increase treatment or hydraulic capacity), administrative and managerial support (monitoring and reporting assistance, training, legal/organizational support), and connections (retiring a failing plant and conveying flow to another facility). Johnston and Koerner explained the team will build representative "problem scenarios" (for example, pond systems with algal TSS problems vs. mechanical plants with clarifier issues), map plausible solutions for each scenario, assemble unit-cost data from engineering reports and other sources, normalize costs for time and scale, and then apply unit costs to each inadequate facility to estimate a statewide total.

Multiple advisory-group members urged the team to supplement Division of Financial Assistance (DFA) engineering reports with other sources: local engineering studies, internal utility reports, RSMeans and literature values, and focused surveys of operators. Presenters said they are already exploring additional sources and would consider technical assistance and legal costs similar to those included in the drinking-water needs assessment. Panelists also discussed using clustering and spatial analyses to evaluate whether some plants are better retired and connected rather than rebuilt.

On OTS (septic) replacement, Koerner outlined two primary opportunities the team will map: septic-to-sewer connections (extend collection to parcels and convey to an existing plant) and septic-to-community-cluster systems (group parcels served by a packaged treatment-managed by a permitted responsible management entity). The team plans to use a University of Massachusetts Amherst machine-learning model to locate likely OTS parcels statewide and then apply feasibility criteria (distance to collection, topography, parcel density) to identify candidate replacement opportunities. Koerner said estimated costs will include capital, planning, engineering and technical-assistance components analogous to the plant-cost approach.

Advisory-group participants recommended the team explicitly consider lower-cost alternatives and managerial solutions before high-capital projects, including: enhanced technical assistance, maintenance/service contracts for septic systems, targeted education for owners (what not to flush, load management), decentralized non-sewered options (composting, container-based sanitation), expanded pretreatment and source-control programs, and remote monitoring or circuit-rider support for operators.

Presenters acknowledged multiple limitations: the statewide method is a blunt instrument that cannot replace site-specific engineering, violations may stem from mixed causes (operations, inflow/infiltration, industrial discharges), some DFA projects omit everyday maintenance costs, and administrative/monitoring deficiencies are difficult to generalize. The team invited advisory-group feedback on selection criteria for representative solutions and on how to handle administrative violations and non-infrastructure interventions.

The project schedule presented to the group includes delivering the Phase 1 report to the State Water Board on or about 2025-06-30 for internal review; the Board review was described as likely to take two to three months, with advisory-group access and public release expected in early fall. Presenters said the work will be iterative: Phase 2 will refine methods, incorporate additional data sources and model outputs (including the UMass OTS model), and support mapping and cost estimates for prioritized locations.

Ending: The contractors asked advisory-group members and sector representatives (operators, technical assistance providers, associations) to provide local engineering reports, cost data, and suggestions for feasibility criteria and solution-selection weights. Staff and contractors invited follow-up during scheduled office hours and in July's advisory-group meeting, which will recap Phase 1 and present further methodological detail.