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State health officials say wastewater plant outfalls drove most of 2025 shellfish downgrades
Summary
Department of Health staff told the Leadership Council that 918 acres of shellfish growing beds were downgraded in 2025—the second‑largest net loss on record—and that 63% of Puget Sound's prohibited acreage is associated with wastewater treatment plant outfalls. Officials described technical steps and funding gaps to reduce prohibited footprints.
State Department of Health (DOH) staff briefed the Leadership Council on 2025 shellfish growing‑area classification changes, saying the year saw a net loss of 909 acres (918 downgraded, 9 upgraded) concentrated around Port Blakely and Port Madison largely because of increased flow and bacteria at nearby wastewater treatment plants.
"Sixty‑three percent of our prohibited areas in Puget Sound are based on wastewater treatment plant outfalls," DOH presenter Scott said, explaining the program assumes a worst‑case failure of disinfection when setting prohibited zones and uses post‑treatment effluent sampling and modeling or dye studies to calculate protective closure footprints.
Marita, a DOH water quality specialist, walked the council through five strategies the agency encourages to shrink prohibited areas: increase initial dilution (diffusers), eliminate discharge during upset conditions (holding tanks/valving), improve treatment and disinfection, extend or remove outfalls (land application), and reduce inflow and infiltration to decrease flows at the plant. She described precedent examples where upgrades and outfall changes narrowed prohibited areas.
Council members pressed DOH on data and funding: Scott said plant sampling prior to disinfection is infrequent and more systematic data would improve closure estimates, and both DOH and staff argued that NEP/competitive grant funding for PICS programs is not a sustainable, ongoing source for local sanitary programs. DOH and council members discussed the need for technical assistance and possible legislative engagement to secure sustained resources and engineering support for small utilities.
DOH asked for partnership support to prioritize targeted technical assistance, data collection and potential legislative or budgetary approaches to help utilities implement outfall strategies and conditionally approved area management plans.
