The City of Seattle is updating its Stormwater Code and Manual to align with the State of Washington Department of Ecology rules and the Ecology Phase 1 Municipal Stormwater permit. A first draft addressing equivalency with Ecology will be unveiled this July. A public review period, scheduled from July 8 to August 5, invites community feedback, and a public meeting is slated for July 15. Details on the upcoming review and meeting are on the Seattle Department of Construction & Inspections website.
Post-public feedback, a second draft of the code and manual will be shared in January 2026, intending to address non-Ecology-related items. The City Council, the Mayor's Office, and Department Directors await the final drafts. For those looking to stay informed, signing up for the SDCI Stormwater Code Updates Listserv is recommended for updates on milestones, documents, and public meetings.
The mandated updates come as a condition of the Ecology Permit, which enforces the National Pollutant Discharge Elimination System (NPDES) requirements. Revisions to the existing codes aim to improve stormwater management, construction site runoff controls, pollution prevention, and enhance flow control and source control practices. The overarching goal is to manage better the impact of new developments on Seattle's unique environment.
As per the described timeline, the City Council is set to review the legislation in the spring of 2026 with an effective date of July that same year. The updated regulations will supersede existing codes and Director's Rules, which are overseen by the Seattle Department of Construction and Inspections (SDCI) and Seattle Public Utilities (SPU). Another comment period is scheduled for the winter of 2026 to ensure thorough public engagement.
