Wasco council adopts wastewater master plan; consultant says plant underused, digesters undersized

The Wasco City Council voted to accept a final wastewater master plan that assesses collection and treatment systems, models future growth and sets a 25-year capital improvement schedule.

Consultant John Kular summarized the plant and collection-system findings: the wastewater treatment plant is operating at roughly 45–50% of permitted treatment capacity, average flows are about 1.5 million gallons per day with seasonal peaks, and the plant meets current discharge standards. Kular said the plant’s digesters are undersized and were identified as the only treatment equipment that is both undersized and in need of capacity attention; the plant otherwise meets standards and does not currently require a treatment-technology change.

Kular described the collection system as roughly 50 miles of gravity sewer with three lift stations. Modeling identified a persistent capacity limitation in a long segment on Seventh Street that causes surcharges at peak hours and several “trouble spots” related to flat sewer slopes and grease buildup from food-service businesses. He recommended targeted capital projects and lift-station adjustments; one near-term recommendation was to adjust pump sizing and controls in a lift station that is underused to limit sewage sitting in pipes and the formation of hydrogen sulfide, and to reduce excessive pump cycling where pumps are running frequently.

During public comment, resident Michael Dela Torre asked about treated effluent application to farmland. Kular explained that Wasco land-applies secondary-treated effluent under the city’s permit: solids are removed and wastewater undergoes biological treatment; the resulting effluent is applied to crops that are not directly consumed by people (typically animal feed or tree crops where the edible portion does not contact irrigation water). Kular pointed residents to the State Water Resources Control Board and the city for permit and monitoring documents.

Council members noted aging equipment and asked about funding. Staff said digester expansion has not yet been budgeted as a CIP project but that long-term planning (including a previously-identified $4.2 million oxidation-ditch expansion option) and ongoing rate studies factor in depreciating assets and future needs. The council adopted the plan by resolution and directed staff to incorporate recommended projects into the city’s capital program and rate planning.