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Thurston County, Washington

The content on the Thurston County website is currently provided in English. We are providing the “Translation” for approximately 10 languages. The goal of the translation is to provide visitors with limited English proficiency to access information on the website in other languages. The translations do not translate all types of documents, and it may not give you an exact translation all the time. The translations are made through an automated process, which may not result in accurate or precise translations, particularly of technical and legal terminology.

Community Planning and Economic Development

There are many types of stormwater facilities. Common types are pictured below. They often look like natural features, but are engineered to move runoff away from homes and streets, and filter out pollution like vehicle fluids and lawn chemicals before it flows into our drinking water aquifers, streams, rivers, lakes or Puget Sound. For more information, see How to Identify and Maintain Your Neighborhood Stormwater Facility.

Wet ponds hold water year-round. Dry ponds may look like an open field until the rainy season. Many have underground pipes and catch basins, to move water and filter it. All are engineered to drain and treat stormwater in the area where they are built.  Learn more about  Wet & Dry Ponds.

Well-maintained stormwater pong with grass and cattails.
Full stormwater pond with a fountain in front of a house.
Dry, grassy stormwater pond in front of a house.

A swale is an engineered ditch with very specific slopes, bottom width and soil requirements. A ditch is a v-shaped open channel. A culvert is a drain pipe under the road.  All three are designed to quickly move rain off of roadways. Grass helps filter pollution like vehicle fluids and lawn chemicals from runoff before it gets into our drinking water aquifer or nearby water bodies. That's why we don't fill them with rocks or dirt.  Learn more about Ditches & SwalesCurb Cuts & Sidewalk UnderdrainsCompost Amended Vegetated Filter Strips (CAVFS).

Gravel ditch alongside a road with a pipe running through it to divert rainwater runoff.
Shallow grassy ditch, or swale, to collect rainwater runoff from adjacent road.
Grassy ditch to collect rainwater runoff from adjacent road.


Catch basins are access points to the stormwater drainage system. They are underground, so the part you see is the drain or grate above.  Catch basins keep heavy debris out, while letting water in. They are connected to pipes that flow to ponds or natural areas. Some catch basins have filters that use charcoal or other types of treatment media that filter polluted runoff. Learn more about Catch Basins & Dry Wells,  Storm Vaults,  Biofiltration Systems,  Oil-water Separators,  Treatment Devices.

Looking down into an in-ground stormwater vault used to capture rainwater runoff from hard surfaces.
Storm drain located in a grassy area.


Stormwater vault with cylinders used to capture and treat rainwater runoff from hard surfaces.
Roadside stormdrain blocked by pine needles.



A culvert is a pipe under the road. It simply connects one ditch to another and is open to the environment on either end. A pipe is attached to a structure (like a catch basin or pond) on at least one end. Learn more about Pipes, Culverts & Slotted Drains and Level Spreader & Diffusers.

Pipe running under grassy area and sidewalk to divert rainwater runoff from hard surfaces.
Pipe in wooded area used to diver rainwater runoff from hard surfaces.


These features tend to look more natural while still providing flood-control and filtration processes and include:

  • Permeable pavement has a dual purpose of providing flow control and treatment. It eliminates runoff by allowing water to seep through, and acts as a filter.
  • Rain gardens or bioretention helps filter pollutants and also reduces or eliminates runoff. 
  • Learn more about Permeable Pavements,  Bioretention and Constructed Wetlands.
Permeable concrete or concrete made in such a way that water can seep through it.
A rain garden next to a road. A rain garden has special soils and plants to help clean polluted rainwater runoff.