Permit updates focus on cleaner stormwater for growing communities

Feedback sought for state’s municipal stormwater permits and guidance manuals

Stormwater runoff is a leading pollution threat to rivers, streams, lakes, and Puget Sound in urban areas of Washington. As rain and snowmelt runs off buildings, paved roads, and parking lots, it increases in speed and volume, and can pick up pollution such as oil, fertilizers, pesticides, tire wear, trash, and pet waste. These pollutants and higher flows are carried into local water bodies, where they can harm water quality and habitat.

To manage this stormwater, Ecology has municipal stormwater permits for the state’s most populated cities and counties. The permits are aimed at reducing stormwater pollution at its source, treating it, and controlling volume and flow, so cleaner water goes into creeks, rivers, lakes, groundwater, and Puget Sound.

view of intersection with vegetation along curbs

This Marysville intersection is a stormwater project that received Ecology funding. The green infrastructure helps reduce the pollution that reaches Ebey Slough.

The regulatory approach in these permits is programmatic and a holistic approach to stormwater management, which is different from the typical water quality permit. Municipal stormwater permittees are required to develop and implement Stormwater Management programs, rather than meet a specific limit for each pollutant at the end of a pipe.

Municipal stormwater permits are divided into three categories, based on population and geography:

  • Phase I permits include incorporated cities with a population over 100,000 people and unincorporated counties with populations over 250,000 people.

  • Western Washington Phase II and Eastern Washington Phase II permits are for smaller urban areas.

We separate the Phase II permits into East and West because of the differences in climate and rainfall patterns.

We update the permits every five years. We also have the Eastern and Western Stormwater Management Manuals available for comment — these critical documents provide the guidance necessary for local stormwater managers to implement the many parts of the permit.

For this permit cycle, we are proposing a number of important updates to address specific pollutants and ensure that as communities develop, change, and grow, work is being done to invest in proper stormwater management and protect water quality.

The investments communities make into stormwater programs and infrastructure pay off. By supporting research, implementing best practices, and planning for the future, cities and counties are truly our partners in achieving cool, clean water across the state.

- Vince McGowan, Ecology’s Water Quality program manager

Highlighting proposed changes

To review all proposed changes for the permits and manuals please view the draft materials on our municipal stormwater permit reissuance webpage. We are highlighting some of the proposed changes below. We are also proposing to add two municipalities to the Phase II permit based on population growth and meeting the criteria for coverage. The proposed new permittees are the cities of Yelm and Ridgefield.

Responding to 6PPD

While efforts are ongoing to find a safe alternative to 6PPD in tires, we are continuing the research and studies needed to learn how best to respond in the meantime. Based on what we have learned to date, we are proposing updates to the stormwater permit requirements and guidance in the manuals that will help the amount of tire wear particles that enter the stormwater system. To learn more about all of Ecology’s work to address 6PPD, visit our 6PPD webpage.

Many of the existing best management practices (BMPs) in the permits and manuals are effective at addressing tire wear particles, including 6PPD, in stormwater runoff. The following updates will help further reduce the amount of pollution in road runoff, including tire wear particles, from reaching local waters in the near term and long term:

  • Requiring more new development and redevelopment projects to incorporate stormwater management BMPs, including Runoff Treatment and Flow Control BMPs
  • Increasing the amount of stormwater retrofits for existing development
  • Adding a street sweeping requirement
  • Requiring a Stormwater Management Action Plan, which includes planning for high priority receiving waters and identifying priority stormwater management activities, including transportation-related projects

Updating requirements for new development and redevelopment statewide 

Construction site showing construction vehicles and people in a large, wide ditch

With Ecology funding, this stormwater retrofit vault project in Kirkland will treat a 49 acre basin

Including stormwater management BMPs, such as runoff treatment and flow control, in the planning for new development and redevelopment projects is the most cost effective and efficient way to manage stormwater. The updates we are proposing to these parts of the permits and SWMMs will result in more stormwater treatment.

In Western Washington, we are proposing that the amount of new plus replaced hard surfaces be considered when determining if the project is large enough to require stormwater management BMPs for the site. Currently, we only require the amount of new hard surfaces be considered when determining if stormwater management BMPs are required.

In Eastern Washington, developers are currently only required to include stormwater management BMPs if the project disturbs one acre or more. The proposed updates to the eastern permit and manual will require the developer to consider the amount of new plus replaced hard surfaces, even if the land disturbed is less than one acre, when determining if the project is large enough to require stormwater management BMPs for the site.

These proposed updates to the new and redevelopment requirements will result in more sites incorporating stormwater management BMPs, which will result in cleaner water and healthier flow rates entering the receiving waters.

The proposed changes are different for each permit, with the specific details in the draft materials.

Increase stormwater retrofits for existing development

Existing development built before stormwater management requirements were in place continues to leave a legacy of pollution that impacts the state's waters. The recent research findings about the toxicity of 6PPD to aquatic species highlights the need to take actions now to help to prevent further declines in fisheries and water quality.

Our stormwater retrofit proposal focuses on the Western Washington permittees:

For Phase I permittees, we are refining the requirements for retrofits, with a focus on flow control, runoff treatment, and low impact development (LID) stormwater projects or substantial maintenance projects.  We are also proposing to incentivize watershed collaboration, benefits to overburdened communities, and projects in high pollution generating transportation areas.

For Phase II Western Washington permittees, we are proposing a new program as part of their permit, Stormwater Management for Existing Development. We have designed a scaled level of effort for retrofits, to address the variety of Phase II permittees: five acres of land “managed” per 50,000 people. This program will lead to more stormwater retrofits.

Prevent pollution with street sweeping 

Street sweeper dumping into a dumpster in a parking lot

Street sweepers, like this one in Mukilteo, pick up trash and other pollution before it enters stormwater systems.

Recent studies show the effectiveness of street sweeping as source control to prevent pollutants from entering the stormwater system. We are proposing a street sweeping requirement for public roads and parking lots in high priority areas.

Addressing PCBs and PFAS

Significant national and statewide efforts are taking place to tackle PCBs and PFAS pollution. The proposed permit updates incorporate recent guidance on how stormwater permittees can prevent these pollutants from coming into to contact with stormwater or being discharged through municipal stormwater systems. To learn more about efforts to address these chemicals visit Ecology’s webpages: PFAS webpage and PCBs webpage.

Environmental Justice

The municipal stormwater permits currently include requirements and guidance on identifying and engaging with overburdened communities that fall within a city or county’s permit coverage area. We are continuing our efforts to ensure the state’s stormwater management program better supports overburdened communities. We are proposing updates related to environmental justice in how retrofits are prioritized, how education and outreach is performed, and how public involvement programs are implemented.

Attend our workshops

We held a series of public workshops over the past year as we developed the draft permits. Now, we are holding another round of workshops that include public hearings so you can provide formal oral testimony. We are holding four virtual workshop/hearings and two in person workshop/hearings. Full meeting details are on the permit reissuance webpage. Oral testimony provided during the hearings receives the same consideration as written comments.

Eastern WA permit and manual focus
Virtual hearings

  • Sept. 18, 9 a.m. 
  • Nov. 6, 1:30 p.m. 

In person hearing

  • Oct. 3, 9:30 a.m. - Moses Lake Civic Center

Western WA permit and manual focus
Virtual hearings

  • Sept. 18. 1:30 p.m. 

  • Nov. 6, 2023, 9 a.m. 

In person hearing

  • Oct. 17, 2023, 9:30 a.m. - Lacey Community Center

Provide comment 

close up of stormwater drain that says dump no waste storm drain to river city of Wenatchee

The draft permits and stormwater manuals are available for review and public comment from Aug. 16, 2023, through 11:59 p.m., Nov. 10, 2023. Detailed information on how to comment is on the permit reissuance webpage.

  • You can provide online comments via eComment.
  • Written comments must be postmarked by Nov. 10, 2023.
  • Please reference specific permit or manual text when possible.