Municipal General Stormwater Permit

The Clean Water Act is the primary environmental law that protects our communities and waterways against all types of water pollution, including stormwater pollution from various sources. The Washington Department of Ecology (Ecology) implements and enforces the Clean Water Act in the Puget Sound region. Ecology issues Clean Water Act stormwater Permits to municipalities throughout Puget Sound and works with Permittees to ensure compliance. Permittees must be held accountable to Permit requirements to control their stormwater pollution. 

Which Municipalities Are Regulated in Puget Sound?

Ecology developed two General Permits for Western Washington municipalities: a Phase I and a Phase II Permit. Phase I included the first Permittees in 1995. They had the largest population sizes and densities at that time: King County, Seattle, Tacoma, Pierce County, Snohomish County, and Clark County. The Phase II Permit came later, in 2007. The Phase II permit covers all other municipal jurisdictions that Ecology determines must regulate their stormwater discharges.

What Do Permittees Have to Do?

All permittees must implement a Stormwater Management Program and take certain steps to protect their communities from stormwater pollution. Permittees must map their stormwater infrastructure, report known pollution issues to Ecology and fix those problems, engage in stormwater planning projects, perform education and outreach to communities about stormwater, and inspect businesses to stop illicit discharges to the storm sewer system. Special protections are required for water bodies that are polluted and have a pollution plan in place. Permittees are also required to use green infrastructure to treat and control stormwater pollution.

A pipe discharges stormwater into the Puget Sound. Photo courtesy Puget Soundkeeper

Build For the Future

Puget Soundkeeper (PSK) and Washington Environmental Council (WEC) brought a legal challenge that resulted in Ecology requiring Phase I and II Permittees to update their local development laws, beginning in 2012. All permittees were required to make LID principles and practices the “preferred and commonly used approach” for new development and redevelopment by the end of 2016. This meant writing LID into local laws that govern development, redevelopment, and new construction projects. 

When we learned that Ecology would not monitor or enforce the LID code update requirement, PSK and WEC created the Nature’s Scorecard: Low Impact Development Code Update Report to track and report on whether cities and counties were complying. This work was not funded by the government. It ensures regulatory compliance with Clean Water Act requirements. As a result of our work, many municipalities improved their code to require more green stormwater infrastructure. 

Fix Mistakes of The Past

Stormwater retrofits install gray and green stormwater infrastructure to treat and control pollution from our developed areas. Municipalities throughout Puget Sound have implemented stormwater retrofits since at least the 1980s. In 1995, Ecology began requiring our largest communities, the Phase I Permittees, to do stormwater retrofits. 

“Structural Stormwater Controls” is a term of art defined by Ecology in the Phase I stormwater permit, which encompasses stormwater retrofits and other projects that benefit our waters.

Ecology defined 11 types of Structural Stormwater Controls (or SSCs) in the Phase I Permit (Appendix 12). All eleven project types (Types #1–11) serve one (or more) of four different beneficial functions: they provide flow control, reduce toxic pollution, restore natural ecosystems, or maintain and preserve existing structures.

Nature’s Scorecard 2022 combines the 11 SSC project types as defined by the Municipal General Stormwater Permit into four “function types,” for ease of public consumption.

Visit our SSC Glossary of Terms to learn more about these four different function types of local stormwater pollution controls. 

Stormwater pollution is caused when rainwater falls or washes over impervious surfaces (like streets) and picks up pollution (including pollutants from cars), washing it into our waterways. Stormwater retrofits treat and control this polluted stormwater runoff. Photo courtesy Puget Soundkeeper

Phase I Permittees generally have stronger stormwater Permit requirements than Phase IIs. A key example is the Structural Stormwater Controls requirement for Phase I Permittees. In 1995, Ecology required Phase I’s to implement a Structural Stormwater Control program. In 2007, Ecology defined a list of types of projects that qualify as Structural Stormwater Controls under the Phase I Permit. In 2019, Ecology established a minimum level of effort for Phase I’s by implementing a points system assigning point values to different Structural Stormwater Controls projects. Phase I’s were required to earn 300 points each permit cycle. To date, however, Phase II’s do not have any SSC requirements.  

The Department of Ecology has recognized that “addressing stormwater impacts from new development and redevelopment at the site and subdivision scale will not adequately address legacy impacts from previous development patterns and practices…It is clear that we cannot protect the state’s waters without also addressing degradation caused by stormwater discharges from existing developed sites. For that reason stormwater programs must include planning and developing policies that address receiving water needs, including development of policy and regulations, and [stormwater] retrofit provisions.”