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Reducing stormwater pollution, the growing threat to water quality in King County

Find out why polluted stormwater runoff is a threat to regional water quality and aquatic life and learn what King County plans to do to keep the waters clean.

Keeping our water clean is very important for the health of communities and the environment in King County. One of the biggest problems we face is polluted stormwater. When it rains, the water washes away harmful things like motor oil, pesticides, and pet waste into our rivers and Puget Sound.

This pollution is causing big trouble for our native salmon and the southern resident orcas. They are struggling to survive because of it.

The problem is getting worse because of climate change. We're having more intense rainstorms, and all that water is washing even more toxins into our waterways.

To fix this, King County scientists are working with partners to find the best ways to reduce stormwater pollution. They are part of an initiative called Clean Water Healthy Habitat, which aims to make smart investments to protect our water and wildlife.

By working together, we can make a difference and keep our water clean and safe for everyone.

Why polluted stormwater is a growing threat to water quality

Rain is naturally filtered when it falls on undeveloped land.
Landscape illustration showing rain falling on natural lands with naturally filtered stormwater flowing into Puget Sound, with its marine animals and plants
As our region continues to grow, more rain is falling on paved surfaces, pushing more pollutants directly into waterways. Landscape illustration showing rain falling on a mix of natural lands and city with some pollution sources including motor oil, metals, yard chemicals and pet waste flowing into Puget Sound, with its marine animals and plants
At one time, sewage was the biggest threat to water quality in King County. But over the past six decades, we’ve built a regional system that can treat more than 66 billion gallons of wastewater and stormwater each year. Landscape illustration showing rain falling on a mix of natural lands and city with some pollution sources including motor oil, metals, yard chemicals and pet waste flowing through wastewater treatment and out into Puget Sound, with its marine animals and plants
The far bigger threat today is the estimated 118 billion gallons of polluted stormwater that doesn’t get treated, carrying toxins into rivers, lakes, and Puget Sound, threatening survival of native salmon and southern resident orcas. Landscape illustration showing rain falling on a mix of natural lands and city with some pollution sources including motor oil, metals, yard chemicals and pet waste flowing into wastewater treatment system and sewer overflow into Puget Sound, with its marine animals and plants

How you can help

There are personal actions you can take to help keep polluted stormwater out of our waterways.

Illustration of a car and tools
Maintain your car: Fix oil leaks and reduce emissions
Illustration of a seed bag, flowers and butterfly
Practice natural yard care
Illustration of a car in a carwash
Wash your car at a commercial carwash
Illustration of a dog with her owner picking up pet waste with a bag
Pick up pet waste

Related information

Clean Water Healthy Habitat

Executive initiative to benefit people, salmon and orcas that call our region home.

Protecting Our Waters

Preventing stormwater pollution from the sewer system

30-Year Forest Plan

Priorities and goals for forests in King County

Stormwater and surface water management

Services and contact information
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