NPDES Stormwater Permit

National Pollutant Discharge Elimination System (NPDES)

The NPDES permit requires the City to take numerous actions to reduce the amount of polluted surface and stormwater runoff flowing into our creeks, streams, rivers, and groundwater. This Permit is issued to the City by the Washington State Department of Ecology and satisfies a mandate within the Federal Water Pollution Control Act of 1948. Due to growing public awareness and concern it was amended in 1972 and is now commonly known as the Clean Water Act (CWA). 

This permit requires the city to:

• Provide Outreach and Education: work with people and businesses to promote daily activities that reduce stormwater pollution.
• Inform and involve the public: give people the opportunity to weigh-in on how we meet permit requirements.
• Respond to spills and seek out cross-connection pipes: this activity is called an "illicit discharge detection and elimination program (Spill Response).
• Review development projects: ensure stormwater facilities are built to City standards, and that construction activities don't pollute stormwater.
• Inspect and maintain public facilities: inspect and clean infrastructure, and make repairs if necessary.
• Inspect and ensure private facilities are maintained: inspect private facilities and ensure property owners maintain and make repairs if necessary.

NPDES Municipal Stormwater Permit

Learn More! Water Cycle Glossary of Terms

Join your neighbors across the city to keep your local storm drains clear of debris to reduce flooding and protect waterways. The Adopt-A-Drain (AAD) Program online tool lets you adopt a storm drain in your neighborhood.

What does it mean to "adopt" a drain? By adopting a drain you will be making a commitment to monitor and maintain a drain of your choice. Volunteers dedicate around fifteen minutes, twice a month, to provide care to their drain. We ask that you make a volunteer profile so we can keep track of the amazing work you've put into building a stronger and cleaner community!

As a volunteer you will be able to create positive impact by: 

• Preventing flooding in your neighborhood by keeping drains free of debris.
• Preventing pollutants from entering our wetlands, streams, lakes, Snoqualmie River, and the Puget Sound, which impact the habitat for fish and other wildlife.
• Helping the city maintain our infrastructure, especially during fall months when rain increase and falling leaves block the drain.

Getting Started

Find Your Storm Drain

Before you clear your first drain, sign up through our partnership with Hamline University of Minnesota Adopt-a-Drain to be a part of the national movement to reduce urban flooding and protect our waterway.

We suggest that when choosing a drain, pick one that will be easy for you to access and take care of. This could mean picking one near your home, school, business, or somewhere you go frequently.

Next Steps to Clear a Storm Drain

1.  Helpful Tools for Cleaning: You might want these tools for cleaning your drain - broom, rake, trash grabber, leaf claws, work gloves, safety vest, dustpan, and a pail or yard waste bag. If you need supplies let us know, we have some grabbers and and leaf claws available - email us and we can help.

2.  Learn about your Storm Drain: there are several types of storm drains. Most drains are located next to the curb and have a metal grate to prevent debris from falling in. They can be rectangular or circular.  We ask that you never remove the grate or otherwise attempt to clean the inside. Clean only on top of the storm drain grate and the area around it.

3.  Clear your drain only if it is safe. If the drain is still clogged after you've removed the surface debris, call 425.939.8040 or send an email with location and as much detail as possible.

4.  Safety First: there are over 2,807 storm drains in the city, so we really appreciate volunteers taking care of the drain in front of their home. 

• If possible, clear the drain before it starts raining.
• Stand on the curb when clearing drains, not in the street. We only ask you to clean curbside storm drains. Please don't clear drains on major streets and arterials.
• Wear gloves and always use a broom or rake to clear the drain. Never use your hands to move debris.
• Use a dustpan, shovel, or a trash can lid to pick up debris.
• Put excess leaves from the parking strip into the yard waste container or paper lawn & leaf bags and set out for collection.
• Put polluted street leaves, trash, and other debris into the garbage.
• Avoid items that have the potential to be hazardous or cause injury, call 425.939.8040 to report a problem.

5. Separate and Dispose of Waste: To dispose of waste, separate it into three categories and place it in the appropriate receptacle - trash, recyclables, and compostables (leaves, grass clippings, and sticks). When in doubt, especially if it's grimy, throw it in the trash.

6.  Keep in Touch: Please help us track the impact of adopt-a-drain by estimating the amount of debris you collection when you clean your drain(s). Report that amount to us at least twice a year - at the start of winter and at the end of spring - by logging in to your account and clicking on "tract your impact." The wa.adopt-a-drain.org shows our collective impact. We can accomplish a lot together and it's important to see results.

If you take any great photos when you're out there cleaning you drain, share them with us and follow us on social media - Facebook, Instagram, Twitter.

7. Feedback: We want to hear from you! Please take a moment to provide us with feedback on how the program is doing. We are constantly striving to improve our program and your feedback will be greatly appreciated.

Adopt-A-Drain Feedback Form

SWMP Annual Reports

All Reports

2026 Submittal Certification

2025 Submittal Certification
2024 Submittal Certification
2023 Submittal Certification
2022 Submittal Certification
2021 Submittal Certification
2020 Submittal Certification
2018 Submittal Certification
2017 Submittal Certification
2016 Submittal Certification
2015 Submittal Certification

2026 DRAFT SWMP Plan

If additional accessibility accommodations are required, please contact stormwater@duvallwa.gov or call (425) 788-3434.

Small Actions Add Up to Big Change

Our actions within our watershed have a direct impact on our wetlands, creeks, streams, lakes, the Snoqualmie River, and the Puget Sound. The City of Duvall and local environmental groups are making a significant effort to restore the local environment and protect our remaining aquatic habitat.

Keep water safe and clean by preventing pollution at its source. Stormwater run-off carries oil and grease, fertilizers, pesticides and other toxic chemicals that collect on our roads, rooftops, and property. What we do on the land ends up in the water. You can help keep our waters healthy by planting trees, scooping up at your  pet, or stenciling a storm drain or adopting a storm drain.

Please continue reading for ways on how you, as a Duvall resident, visitor, or business owner, can make a difference where you live and where you work.

Public Participation

The city encourages public comment and participation in the development and implementation of the SWMP. We plan to utilize the following venues in an effort to keep our residents informed on the progress of the SWMP, so they can provide comments and input as the SWMP develops:

• This webpage
• Updates through the city's newsletter
• Future public meetings to let the community provide input

Stormwater Runoff Awareness, Attitudes & Behavior Survey Results (2019)

Residential Car Washing and Stormwater

When a car is washed on a paved surface, like in a driveway or in a parking lot, the soap, detergent, automotive fluids, oil, heavy metals, and roadway dirt that are rinsed from the vehicle goes straight into nearby storm drains. Storm drains convey water to the nearest river or stream without treatment. This contaminated runoff, even runoff containing biodegradable soap, can cause significant harm to aquatic plant life, fish, and other animals. You can wash your car and prevent stormwater pollution if you: Park the car on grass or an area where the water can filter into the ground and not run off to the storm drain. If the driveway drains to an area where it can infiltrate, that works too. Divert the drainage away from the storm drain. Use a hose with a shut-off valve to reduce possible runoff from the grassy area. Dump your soapy water out in the sink or on an area where it will filter into the ground. If you don’t have a good place at home to wash your car, we ask you to take it to a commercial car wash (either self-serve or machine wash) where the wash water drains to the sanitary sewer.

Car Wash Kits The City of Duvall is no longer providing Fundraising Car Wash Kits. The Car Wash Kit was intended to prevent pollution from entering our storm drainage system, which drains to our local streams and the Snoqualmie River. Studies show that fundraising car washes still may allow soap and dirty wash water to flow to storm drainage systems. Since State and Federal regulations make it illegal to dump any wastewater to the storm drainage systems, public or private, the City of Duvall asks that you check out these alternative fundraising ideas as alternatives to holding a car wash. Alternative Fundraising Ideas Contact the City of Duvall by email if you have any questions.

Stormwater Facts

• Puget Sound is the largest estuary in the continental United States by water volume. The Puget Sound coastline lies within 12 Washington State counties; a total of 14 counties are within the entire watershed.
• Did you know the biggest pollution challenge to Washington’s streams, lakes, and marine water in urban areas is stormwater? The stormwater from one outfall may collect drainage from a large area with hundreds of homes, businesses, and parking lots. The accumulation of all the pollutants that run off those areas in the rain, especially after a dry period, adds up to a lot of pollution. We all need to be mindful of how we wash cars, pick up after our pets, and take care of our yards so we can prevent pollution.
• Water that enters the storm drain in Duvall and other urban areas, goes directly through the pipes to streams, lakes, bays, and Puget Sound. In most areas, the stormwater does NOT go to a sewer treatment plant like the water that goes down the drain inside your house. Stormwater carries all the pollutants with it directly to our surface waters—soapy water and all.

Stewardship Opportunities

Help restore our natural areas to encourage native species regeneration, provide habitat for wildlife, and to provide the cool, clean water which is critical for the native fish that populate our streams and rivers. Volunteer projects such as invasive species removal, native planting and plant maintenance are available in Duvall and across the region.

Here are links to local organizations that coordinate stewardship opportunities:

• King Conservation District
• Mountains to Sound Greenway Trust
• Oxbow Farm & Conservation Center - restoration volunteer days every second Saturday of the month
• Sound Salmon Solutions
• Snoqualmie-Skykomish Watershed Opportunities

Stencil a Storm Drain

Get outside, volunteer, and do your part to help raise awareness about storm water pollution and water quality in Duvall neighborhoods. Individuals, families, and small groups are welcome to sign up and get a reusable kit to paint stencils next to storm drains in their neighborhood.

How does a stencil help? Most storm drains direct water and pollutants to a nearby stream, creek, or the Snoqualmie River, which eventually drains to the Puget Sound. A stenciled drain reminds the community that what goes into the drain will end up in local waterways directly affecting wildlife and people. When people make the storm drain connection, they are less likely to dump pollutants like soaps, paints, antifreeze, and used motor oil into storm drains.

Request a Stencil Kit

Volunteers will receive detailed instructions when you pick up a stencil kit. Kits include a stencil, paint, gloves, safety gear, and a bucket to hold it all.

Form information and to register to pick up and drop off a stencil kit contact Public Works by email

Our actions within our watershed have a direct impact on our lakes, streams, wetlands and the Puget Sound. The City of Duvall and local environmental groups are making a significant effort to restore the local streams and protect our remaining aquatic habitat. Please do your part in keeping our waterways healthy by helping us keep an eye out for illegal activity which can damage water quality. 

How can you help?

• Never dump anything down a storm drain.
• Dispose of yard and pet waste properly.
• Avoid excess use of lawn fertilizer.
• Wash your car on your lawn or at a car wash facility.
• De-chlorinate pool water before draining.
• Dispose of paint, and other household chemical according to label directions.
• Take unwanted oil, paint, gasoline, and other toxic wastes to a household hazardous waste site or recycling center.
• Make sure sanitary, laundry, car wash, and industrial wastes don't drain to the storm sewer.
• Report illicit discharges to the reporting line: 425.939.8040, emergency after hours: 425.419.3748 or email (non-emergency only).

Reporting Discharges & Spills
Please do your part in helping to protect our natural waterways. Report any spill, illicit discharges or illicit connections to our natural waterways or storm system by calling the city’s spill hotline. City staff understands the need for confidentiality, so calls can be anonymous. However, please provide as much detail as possible about the spill or illegal activity including the date, time, location, a description of the spill or illegal activity and a description of the pollutant.

All city storm drains flow into natural waterways. So it is very important to report illegal dumping or even accidental spills in our roadways, storm systems or natural waterways.

Illicit Discharges An illicit discharge to a stormwater system is the discharge of pollutants or non-stormwater materials to storm systems via overland flow or direct dumping of materials into a storm drain. Some examples of illicit discharges include run-off car washing or dumping motor oil, antifreeze or paint in or around a street or storm drain.
Illicit Connections An illicit connection to a stormwater system is the discharge of pollutants or non-stormwater materials into a storm system (pipes, catch basins, ditches, etc.) via a pipe or other direct connection. Sources of illicit connections may include sanitary sewer taps, wash water from laundromats, car washes, or restaurants and other similar sources.

Private Storm Drainage System Maintenance

The City of Duvall requires property owners to inspect and maintain stormwater systems on their private property. The City inspects private stormwater systems to ensure that they are functioning properly. It is important that property owners maintain these systems to prevent pollutants from entering the drainage system and surface waters of Duvall.

Stormwater systems are designed to collect and control runoff, prevent flooding, and keep pollutants out of surface waters. This benefits everyone by providing safe use of City streets and clean recreational waters to enjoy. Regular maintenance on storm system catch basins, ponds, and ditches is not time consuming or difficult. Contact information for the Storm Utility and the City's minimum maintenance standards are below.

City of Duvall Maintenance Guidelines

All private storm systems are required to meet the Maintenance Standards for Drainage Facilities found in Volume V of the Washington State Department of Ecology (Ecology) Stormwater Management Manual for Western Washington (SWMMWW) found here: Ecology SWMMWW Maintenance Standards for Drainage Facilities.

Questions

For more information about your private stormwater management system, state and local requirements, and the City's Storm Utility please email us.

Low Impact Development (LID)

The low impact development approach to developing land and managing stormwater is to imitate the natural movement of water through a site.

Where forests and natural open spaces have been cleared, and buildings, roads, parking areas and lawns dominate the landscape, rainfall now becomes stormwater runoff, carrying pollutants to nearby waters.

The City has developed a Homeowner's Guide to LID Best Management Practices.