Updating Stormwater Regulations - Project Documents

A Chinook salmon spawning in the reconstructed reach of the Thornton Confluence Floodplain project site. Courtesy Chapin Pier, Seattle Public Utilities, October 2018.
  • What & Why
    We're working on our 2020 Stormwater Code and Manual Update
  • Get Involved
    We're working on our 2020 Stormwater Code and Manual Update
  • Project Documents
    We're working on our 2020 Stormwater Code and Manual Update
  • Background
    We're working on our 2020 Stormwater Code and Manual Update
  • Timeline
    We're working on our 2020 Stormwater Code and Manual Update

Project Documents

The actual Stormwater Code and Manual changes are still to be determined. However, our regulations must be equivalent to Ecology's NPDES 2019 Stormwater Permit (Ecology Permit). We will consider the following topics for our updates:

  • Construction site stormwater runoff control/concrete handling
  • Technical changes to structural stormwater controls
  • Source control
  • Clarification of drainage review for Master Use Permit (MUP) and common plans of development
  • Combined sewer flow control standard/threshold updates
  • Wetland flow control standard
  • Stormwater/combined mainline extension requirement clarification
  • Addition and clarification of definitions
  • On-site Stormwater Management (OSM) list approach