San Francisco Bay board adopted 40% nitrogen‑load reduction permit after decade of science and regional planning

The San Francisco Bay Regional Water Board adopted a nutrient permit in July 2024 that sets aggregate nitrogen reduction goals intended to reduce the potential for harmful algal blooms and low dissolved oxygen events, a board staff presenter said at a State Water Board meeting.

Board staff explained that municipal wastewater treatment plants (about 40 POTWs in the region) historically contributed the majority of nitrogen loads to the bay and that a severe heterosigma bloom in August 2022 — followed by a similar event in 2023 — produced widespread fish kills and public concern. Staff concluded there was “reasonable potential” for effluent nitrogen to cause or contribute to basin‑plan violations of the narrative biostimulatory substances objective; federal permitting rules require effluent limits when reasonable potential exists.

Using modeling and the 2022 bloom as a critical condition, staff translated a protective dissolved‑oxygen criterion into an aggregate load target. Staff said a bay‑wide 40% reduction from the 2022 baseline (about 44,000 kg/day) would reduce nitrogen enough that, even under a severe bloom scenario, sufficient oxygen would remain to protect beneficial uses. The board adopted a bay‑wide compliance approach: if the aggregate load limit is met, dischargers are treated as in compliance; if aggregate limits are exceeded, dischargers with individual exceedances would be in violation.

The permit requires continued monitoring and an ongoing science program funded by the wastewater agencies — staff said the agencies have contributed roughly $15 million to studies over the prior decade and committed to continuing funding of $2.2 million per year. The permit includes interim and final limits, encourages regional planning and coordinated upgrades, and establishes a 10‑year compliance schedule under the state board’s compliance‑schedule policy. Staff noted the compliance schedule was a major topic of stakeholder concern; the regional board directed staff to explore options to allow more time than the maximum 10 years where multi‑benefit projects (for example, water recycling) require longer lead times.

Staff said the board conducted unusually extensive engagement over a decade: phased permits beginning in 2014 and 2019 required monitoring, regional studies and funding for science; the 2019 permit had foreshadowed a need to cap loads in the 2024 permit. Stakeholders included wastewater agencies, environmental groups (some urging deeper cuts), EPA, USGS and many scientists; staff emphasized “joint fact‑finding” and regional collaboration in preparing analyses.

At the July 2024 hearing, the regional board heard more than 50 public speakers, asked questions of staff, and voted unanimously to approve the permit, staff reported. Challenges remain: cost estimates for regional upgrades have been large in public comment (some stakeholders cited multi‑billion dollar regional costs), and agencies pressed for extended time. Staff said the permit’s combined approach — numeric limits, continued science funding and the 10‑year schedule with staff directed to pursue possibilities for additional time when justified — was the path the board adopted to balance science, cost and practicability.

Board staff said implementation is ongoing and will include monitoring, regional planning, and continuing collaboration with regulators, researchers and wastewater agencies.