How We Manage Stormwater

Photo shows a wetland with water and plants in front of an industrial building
Portland may be the Rose City, but we’re just as well known for our rainy weather. We get an average of 37 inches of rain each year. You might wonder, “where does all that rain go?” Read on to learn how rain becomes stormwater, and how Environmental Services manages the challenges it causes.
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What Is Stormwater and Why Do We Manage It? 

A photograph of a green street planter with a tree and various other plants surrounded by rocks while rain comes down from an overcast sky at the curb of 45th Ave and Clay St, a suburban street
Green streets are one of the ways we manage stormwater more naturally in neighborhoods throughout Portland.

In a natural environment, rain is mostly absorbed by plants, soil, and trees. When it rains in the city, the water flows over hard surfaces like rooftops, parking lots, streets, sidewalks, and driveways. It picks up pollution along the way, like oil from cars on the streets. This is called “stormwater runoff.” This stormwater runoff carries that pollution into our rivers and streams. Unmanaged stormwater, which is when the rain has no place to flow safely like into a pipe, ditch, or green street planter, can cause flooding, erosion, landslides, sewer backups into homes and businesses, and sewage overflows into our rivers and streams. This can harm people, wildlife, property, and the environment. 

Important federal and state laws, such as the Clean Water Act and the Safe Drinking Water Act, are in place to protect water quality in our rivers, streams, and groundwater. These laws require us to manage the stormwater runoff created by our urban environment in order to protect both surface waters and groundwater.   

As Portland’s sewer and stormwater services provider, Environmental Services works with residents, businesses, and communities to manage stormwater in Portland to protect water quality, public health, and the environment. It’s all part of our mission: working for clean rivers.

What Does Environmental Services Do about All That Rain?

Portland manages stormwater with a complex network of engineered and natural assets. In addition to hundreds of miles of pipes and ditches (engineered assets), natural areas (natural assets) help collect and soak up a lot of our rainfall. Portland's many acres of wetlands and miles of streams are important parts of the network, along with thousands of sumps and other pollution prevention tools.

We work with nature to tackle urban challenges with green street planters, trees, and natural area restoration. This includes working with property owners and community organizations to fund community projects on private property that promote green solutions in our neighborhoods like adding native plants, building rain gardens, or removing pavement.

We build and maintain thousands of miles of pipes and nearly 100 pump stations that help move sewage and stormwater to our wastewater treatment plant. We select the right tools for managing stormwater in each area of the city based on geography and other factors. That means stormwater management in Southwest Portland may look different from East Portland. 

There are five major ways we manage stormwater.

1. Stormwater Can Soak into the Ground:

In nature, rain soaks into the ground, where it is absorbed by plants and trees. That is possible in the city, too. Environmental Services invests in green streets, tree planting, native landscapes, community projects, and restoration of natural floodplains and wetlands to help create more places where stormwater can be collected, stored, and then slowly soak into the ground. This helps prevent flooding, erosion, and pollution of our rivers and streams. It also helps restore and protect habitats for wildlife, including endangered salmon. For example, green streets are one of the ways we manage stormwater more naturally in neighborhoods throughout Portland. You may see these small rain gardens in your neighborhood. To learn more about why we build green streets, how they work, and how to adopt one in your neighborhood, visit About Green Streets.

2. Stormwater Can Flow into a River or Stream:

Some city storm drains lead directly to a river or stream. This means we need to watch what goes into storm drains! If you wouldn’t dump something in the river (like used paint or motor oil), don’t dump it into a storm drain. Learn how to report spills or pollution going into a storm drain.

Another major source of water pollution is what the rain picks up from our streets, parking lots, yards, and gardens on its way to a stream. Portlanders and property owners play an important role in helping reduce this form of water pollution. Eliminating chemical fertilizers and pesticides from our yards and gardens or regularly maintaining our cars so they don't leak fluids onto the street or driveway are activities that help reduce water pollution.

3. Stormwater Can Go to the Treatment Plant

In many areas of Portland, storm drains lead to pipes that transport that stormwater to the Columbia Boulevard Wastewater Treatment Plant to be treated. Learn more about the collection system and the treatment process.

Environmental Services has thousands of miles of pipes, many of which are 80 to 100 years old. We regularly repair and replace aging pipes and add green streets and other stormwater solutions across the city. Check out our current construction projects.

4. Stormwater Can Be Directed Underground to Replenish Groundwater

Photo looking down an underground injection control facility (UIC). Which looks like a concrete shaft with smalls holes on the side for water to seep out.
A sump is a large, concrete cylinder installed under a street. It collects runoff from streets, and the holes in the sides allow the water to slowly soak into surrounding soil.

Have you ever heard of “underground injection control” or UIC? This is a fancy name for underground structures that collect and filter pollutants out of stormwater before allowing the water to soak into the ground. The water then replenishes groundwater supplies. Environmental Services maintains about 9,000 UICs around Portland. Also called "sumps," these are basically large, cylindrical, concrete tanks with perforated sides (sides with several holes about the size of a softball) that descend generally 30 feet below the street. Storm drains direct stormwater first into a tank that separates out garbage and pollutants and then to the sump where the water soaks out of the many holes into the surrounding soil.

5.  Stormwater Can Be Managed Through Policies and Regulations

Environmental Services creates and maintains policies and regulations for stormwater management that apply to developers, property owners, businesses, and industries. This ensures that appropriate stormwater management facilities get built when properties are developed and helps control pollution to rivers, streams, and wetlands from industrial activities. To learn more about regulations and requirements for property development, refer to the City's Stormwater Management Manual and Source Control Manual.

What About the Stormwater at My Home or Business? 

In addition to the solutions used by Environmental Services, we work with businesses, developers, and homeowners to manage stormwater on private property. Learn about ways to manage rain on your property. Home and business owners can also reach out to us for help with drainage issues on their property.

And you can help prevent street flooding by keeping the neighborhood's street drains clear of leaves and debris. If a storm drain or green street planter inlet needs attention, report it to the PBOT 24/7 Maintenance Dispatch at 503-823-1700 or learn how to Adopt a Strom Drain and clear it yourself. Visit About Green Streets to learn more about the City’s green street maintenance and how you can help.