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Municipal stormwater general permits

Municipal stormwater general permits cover discharges from municipal stormwater systems. These are systems run by public entities that are separated from sanitary sewer systems.

There are four municipal stormwater general permits in Washington:

We will reissue the Phase I and both Eastern and Western Washington Phase II permits on July 1, 2019.

Find out where we are in the reissuance process for these permits.

Phase I Municipal Stormwater Permit

The Phase I Municipal Stormwater Permit regulates discharges from municipal separate storm sewer systems (MS4s) owned or operated by the state's largest cities and counties.

These include:

  • Incorporated cities with a population of over 100,000* people.
  • Unincorporated counties with populations of more than 250,000* people.
*Populations are based on the 1990 U.S. census.

Phase II Municipal Stormwater Permits for Eastern and Western Washington

The Phase II Municipal Stormwater Permits cover the next most populated parts of the state.

We issue two Phase II permits:

Secondary Permittees

The permit also applies to public separate storm sewer systems operated by other types of public entities located in a Phase I or II city or county. Examples include ports, prison complexes, park districts, universities, or diking and drainage districts.

Washington State Department of Transportation (WSDOT) Municipal Stormwater Permit

The WSDOT municipal stormwater permit regulates discharges from state highways, rest areas, park-and-ride lots, ferry terminals, and maintenance facilities within the urbanized areas of the state.

Who's covered under the municipal stormwater permits?

Phase I cities and counties
Western Washington Phase II Cities
Western Washington Phase II Counties
Eastern Washington Phase II Cities
Eastern Washington Phase II Counties


For guidance about applying, changing, or implementing and complying with your municipal stormwater permit see the municipal stormwater guidance page. Stormwater manuals provide stormwater permit implementation and management guidance. For more general stormwater permit guidance, see the stormwater guidance page.

Frequently asked questions

Have a question? Check out our frequently asked questions page.

Stormwater monitoring

Are our permits successful at preventing or reducing pollution from stormwater runoff? Check out the Stormwater Action Monitoring program and our other results on the Stormwater monitoring page.

2019 Municipal Stormwater Permit reissuance

Next steps and reissuance timeline

We anticipate releasing a formal draft with a formal comment period in the summer of 2018.

Timeline: pre-draft input due 9/30/2016, public meetings Feb-Mar 2017, prelim. draft sections for informal comment mid 2017, Formal draft released for comment mid 2018, Permits reissued Aug 2019
Western Washington

Preliminary drafts | Comment period | Public meetingsWatershed-Scale Stormwater Reports | Early input and past public meetings

The Western Washington Phase I and Phase II permits expire on July 31, 2018. After careful consideration of many factors, we have decided to extend the current (2013-2018) Western Washington permits for one year.

The permits will reissue on July 1, 2019, and become effective on Aug. 1, 2019.

  • The extension will allow us to consider information from ongoing research on effectiveness of stormwater management actions, as well as conduct a review of submittals on permit requirements that are due late in the current permit cycle.
  • The extension will allow for more time to engage with the public and stakeholders during the process of permit development.
  • Extending our permit cycle will allow us to reissue the Western and Eastern Municipal Stormwater Permits at the same time, ensuring an inclusive process for the whole state.
In accordance with WAC 173-226-220(3), the current (2013-2018) permits will remain in effect during the extension for all permittees who reapply on-time.

Here are some Frequently Asked Questions on the permit extension and continuing program implementation — primarily for Phase II — although there is applicable overlap with Phase I requirements.

Preliminary drafts available for comment

We have developed preliminary draft permit sections for the Phase I and Western Washington Phase II Municipal Stormwater Permits. Preliminary draft sections of the Stormwater Management Manual for Western Washington (SWMMWW) are also available.

Preliminary draft sections available for comment include: 

Municipal Stormwater Permit sections

NEW: Long-term municipal stormwater planning

SWMMWW (in web format)

Comment period

We are accepting comments on these preliminary draft sections until 11:59 p.m. Jan. 19, 2018, with one exception: we are accepting comments on the “long-term municipal stormwater planning document" until 11:59 p.m. Feb. 2, 2018.

This is an informal comment period; we will not respond to the comments received, but will take them into consideration in developing the formal drafts of the permits. The formal drafts are anticipated to be available for comment in summer of 2018. 

Send comments to: http://ws.ecology.commentinput.com/?id=tkx29 

Or mail hard copies to: 

Municipal Stormwater Comments 
WA Department of Ecology 
Water Quality Program 
PO Box 47696 
Olympia, WA 98504-7696

Public meeting on preliminary drafts

We held an informational meeting (with webinar option) on: 
Oct. 12, 2017 at 1 p.m. 
Department of Ecology 
300 Desmond Drive, Lacey

We held an (in-person) meeting to discuss watershed planning:

Dec. 11, 2017 from 1 - 3:30 p.m. 
Rhodes Center 
949 Market St. 
Tacoma, WA 98402 
Agenda | Document | Presentation | Q&A

Watershed-scale stormwater reports

Phase 1 County’s and participating Permittees developed watershed-scale stormwater plans during the 2013-2019 permit term, these will help to inform the next steps for the watershed effort.

King County’s watershed-scale stormwater plan is due in April 2018 and will be posted here when received.

Clark County Pierce County Snohomish County

Early input and past public meetings

Considerations for initial reissuance input

When we heard there was interest in providing early input on permit changes, we provided the following considerations to help frame the comments:
  • No backsliding permit requirements.
  • Consider status of implementation. Several requirements from the 2013 permits are just beginning to be fully implemented. Consider whether additional implementation time will provide clearer direction for potential future permit changes.
  • Provide suggestions on permit changes that will:
    • Improve understanding/clarity of the requirement
    • Improve implementation
    • Lead to better water quality results
  • Thoughts on whether (and how) to combine the Phase I and WWA Phase II permits.
  • Suggestions for requirements in the permit that do not easily roll into the next permit cycle (e.g. LID code updates, and watershed-based stormwater planning).
  • Provide rationale or justification for any proposed changes or suggestions.
    • Provide relevant data sources or literature if this supports proposals for revisions.
  • Provide input about existing permit language that you view as an impediment to implementation.
  • While always helpful, exact permit language is not necessary.
Ultimately, we are responsible for administering and issuing the permits and will make final decisions on permit language. This early and continuing input will help to inform those decisions.

Past public meetings

We held three public meetings on specific permit topics in February and March 2017. We used the early input we received in fall of 2016 as the foundation to generate further discussion and receive broader input.

Summary notes from each of the meetings are posted below. Presentation handouts:

Feb. 23, 2017 - Summary Lynnwood meeting notes
Lynnwood Convention Center

March 2, 2017 - Summary Lacey meeting notes
Lacey Community Center (also held via webinar)

March 14, 2017 - Summary Vancouver meeting notes
Clark College

In Oct. 2016, stakeholders provided early input to identify areas of the permits that need clarification or improvement. While the early input is informal and responses won't be prepared, we are reviewing input closely and greatly appreciate the time and energy involved in providing it. These early efforts demonstrate a shared commitment to protect and restore Washington's waters.

We have compiled the informal early input received on permit reissuance.

Eastern Washington

Keep in touch with us

Join our municipal stormwater permit listserv to receive updates about our permits.