Stormwater is a problem in Puget Sound—in fact, it’s the number one source of pollution. All the rain that travels over impermeable surfaces, like driveways, parking lots, roads, roofs, piers, and more, is considered stormwater. Every time it rains or snows, massive volumes of stormwater sweep across these surfaces and collect toxic chemicals and trash. By and large, stormwater empties directly down storm drains and flows, untreated, into Puget Sound.  

But that doesn’t mean stormwater pollution is unregulated. In Washington, the Department of Ecology (Ecology) is charged with protecting waterbodies and enforcing pollution limits through permits that uphold the Clean Water Act. One way Ecology does that for municipalities is through the Municipal Separate Storm Sewer System (MS4) permit.  

What is the MS4 permit? Which entities does it impact? What does it regulate? 

The MS4 permit regulates discharges from municipal stormwater systems. These drainage systems are owned or operated by cities, counties, and other public entities, and are different from sanitary sewer systems. Municipal stormwater systems flow directly into water bodies without treatment.  

Illustration of how stormwater moves across urban landscapes
Source: Lower Macungie Township

Urban areas are comprised of many impervious surfaces which disrupt infiltration and prevent groundwater recharge from precipitation. Impervious surfaces concentrate surface flow and increase the frequency and quantity of runoff entering waterbodies.  

This causes increased flooding, loss of habitat, and excessive sediment transport among other issues. Stormwater accumulates contaminates left on the ground, metals, nutrients, pesticides, organic compounds, and trash make their way into waterbodies untreated via the storm water systems. Polluted stormwater discharges negatively impact human health, drinking water, Tribal treaty rights, salmon habitat, shellfish beds, and degrades overall water quality.  

Ecology issues four types of municipal stormwater general permits. Soundkeeper focuses on the Phase I and Phase II Western Washington permits, as these are most relevant to our region. 

The Phase I MS4 Permit regulates discharges from MS4s owned or operated by the state’s largest cities and counties:  

  • Seattle and Tacoma, King, Clark, Pierce, and Snohomish counties 
  • Incorporated cities with populations over 100,000 people 
  • Unincorporated counties with population over 250,000 people (populations based on 1990 U.S. census) 
  • Public entities in a Phase I city like the Port of Seattle and Tacoma.  

The Phase II Western Washington MS4 Permit regulates discharges from “small” MS4s in Western Washington such as Bellevue, Kent, Kirkland, Fife, SeaTac and others.  

Native plantings next to a sidewalk, an example of green stormwater infrastructure that helps to filter polluted stormwater runoff.

Learn more about Phase I and Phase II Permittees by using Soundkeeper’s Nature’s Scorecard report and storymap! This report assesses local stormwater pollution controls, called Structural Stormwater Controls (SSCs), and progress toward regional implementation.

What is a permit cycle? Where are we in that cycle?  

Ecology revisits and reissues these general permits every five years. The 2019 MS4 Permits are set to expire in 2024, so Ecology is preparing for the next iteration of MS4 Permits. It released drafts of the 2024 MS4 Permits in August 2023, kicking off a three-month formal comment period. During the formal comment period anyone from the public could submit oral or written comments that addressed the proposed 2024 MS4 Permits. The formal comment period closed on November 10, 2023.  

Why does Soundkeeper submit comments?  

Soundkeeper submits comments on all types of permits. Submitting comments reflects our commitment to participate in government management and the regulation of pollution that ultimately affects the health of our waterways and communities.  

Comments are also an important way for Soundkeeper to voice our expert position on water quality protection. Comments can ultimately change or influence a project or permit. The process is also key to establishing legal standing, allowing Soundkeeper and others to bring legal challenges when the permit process is complete.  

Most recently, Soundkeeper has brought legal challenges against the MS4 permit in 2007, 2012, and 2019. 

Soundkeeper’s MS4 Comments  

Soundkeeper has a long history advocating for more protective stormwater permits. Soundkeeper commented on several issues during this permit cycle, including the Phase I and Phase II Permit’s inadequacies related to 6PPD-quinone pollution. This chemical comes from the breakdown of tires and is acutely toxic to coho salmon and other fish species. The amount of 6PPD-quinone in our waterways could be greatly reduced with the installation of green stormwater infrastructure like biofiltration, but the Permit failed to require this.  

Soundkeeper commented on the Permit’s problematic point system and how it fails to incentivize all Permittees to prioritize projects in areas that are most at risk of stormwater pollution. We also commented on improving public access to permit information and process and requiring meaningful engagement with affected communities. 

Thank you to our colleagues at Earthjustice, who drafted a comment on our behalf addressing these concerns. In addition, Soundkeeper drafted a letter oriented towards law and policy advocacy that we hold in common with our partner organizations. You can read our full comments here and here.  

What are the next steps? 

Now that the formal commenting period is closed, Ecology reviews each comment and considers it when finalizing the 2024 MS4 Permits. Ecology will publish a Response to Comments document in addition to the final permits, addressing comments submitted during the formal comment period. 

Ecology anticipates issuing the final 2024 MS4 Permits in July 2024. Once Ecology issues the final permits there is a 30-day window to appeal the final permits to the Pollution Control Hearings Board. If no one challenges the permits, they go into effect for the next five years. Stay tuned!   

(Header photo by Tom Reese)