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.
Ditches, Swales & Culverts
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.
Catch Basins, Drains, Grates and Canister Filters
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.
Culverts & Pipes
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.
Low Impact Development (LID) features
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.