Washington's stormwater permits fall under the National Pollutant Discharge Elimination System (NPDES) program, and are managed primarily by the Washington State Department of Ecology ("Ecology").

There are three primary categories of stormwater permits in Washington:

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Industrial Stormwater General Permit (ISGP)

Who?: Industrial Facility Operators
Covers: Industrial facilities where materials/activities are exposed to precipitation

From the Department of Ecology:
“Stormwater can pick up pollution from factories and businesses. Those contaminants are carried into waterways and harm fish and other aquatic life. The National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge permit helps industrial facilities comply with federal and state regulations that reduce pollution. We require most industrial sites in Washington to monitor, measure, and reduce stormwater pollution leaving their site. We use the federal Clean Water Act and state law (RCW 90.48.080) to regulate stormwater at industrial facilities. The permit went into effect on Jan. 1, 2025 and expires Dec. 31, 2029.”

Construction Stormwater General Permit (CSGP)

Who?: Developers, Contractors
Covers: Construction disturbing ≥ 1 acre (or smaller included in a larger plan)

From the Department of Ecology:
“Stormwater runoff from construction sites can carry muddy water, debris, and chemicals into local waterways. Sediments, chemicals, and debris can harm aquatic life and reduce water quality.

We require regulated construction sites to get coverage under the Construction Stormwater General Permit. Following the requirements in this permit helps control and reduce water pollution.

Operators of regulated construction sites are required to:
- Develop stormwater pollution-prevention plans.
- Implement sediment, erosion, and pollution-prevention control measures.
- Obtain coverage under this permit. ‍

‍The current permit went into effect on Jan. 1, 2021 and expires on Dec. 31, 2025.”

‍Municipal MS4 Permits (I, II, and WSDOT)

Who?: Cities, Counties, Universities, School Districts, WSDOT
Covers: Urbanized Areas, Highways, Ferry Terminals, Etc

From the Department of Ecology:
"Municipal stormwater general permits regulate discharges from municipal stormwater systems. These drainage systems are separated from sanitary sewer systems and are owned or operated by cities, counties, and other public entities.

Stormwater is rain and snow melt that runs off surfaces such as rooftops, paved streets, highways, and parking lots. As water runs off these surfaces, it can pick up pollutants that contaminate local water bodies.

There are four municipal stormwater general permits in Washington."

Permit and Reporting Information System (PARIS)

From the Department of Ecology:
“Our Permitting and Reporting Information System (PARIS) database contains information about water quality permits, inspections, enforcement actions, and discharge monitoring reports (DMRs). Both federal National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge permits are included in the database.”

Certified Erosion and Sediment Control Lead Database(CESCL)

From the Department of Ecology:
“This database contains information about individuals who have completed CESCL training, including expiration dates.”

Clear Water provides CESF Operator and CESCL training as well as CESCL inspections by qualified professionals.

Stormwater Monitoring

From the Department of Ecology:
“Stormwater runoff can flow directly into fresh or marine waters, or it may go into a storm-drain system and continue through storm pipes until discharging into the environment. Stormwater management activities include keeping rainwater clean and using best management practices at sites or regional facilities to treat or infiltrate water before it's discharged. Monitoring and tracking stormwater quality helps us understand how well these activities by permittees and/or best management practices are working. We partner with Puget Sound Partnership on the National Estuary Program and the strategic initiatives.”

How to meet CSGP Requirements‍

A PDF guide for construction sites from the Department of Ecology.

Stormwater Management Manual for Western Washington

The online, interactive 2012 Stormwater Management Manual for Western Washington, as amended in December 2014 (the 2014 SWMMWW).

For help navigating applicable permits, reach out to our team.

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