Stormwater Facility Credit

Photo of a bioretention system
Green roofs are living vegetation systems installed on top of buildings to slow the flow of stormwater via soil storage, evaporation and transpiration. Green roofs consist of several layers of material to achieve the desired vegetative cover and drainage requirement.

If your property has a fully functioning, well-maintained stormwater system, you may be eligible to save money on your annual drainage fee. Seattle Public Utilities (SPU) developed the Stormwater Facility Credit Program to recognize privately-owned systems that reduce stormwater flow and/or provide water quality treatment, which help lessen the impact to the City's stormwater system, creeks, lakes, or Puget Sound. If you live in a single family home you may want to consider green stormwater infrastructure for your property.

View the Stormwater Facility Credit Program Flyer (pdf) for a summary of the program. You can also browse our questions and answers, view customer examples, and learn how to apply for the credit.

  • Photo of permable pavement #1Permeable paving is a paving system which allows rainwater to percolate into the underlying soil.
  • Photo of permable pavement #2Permeable paving is designed to slow the flow of stormwater.
  • Photo of permable pavement #3Permeable paving can be used in walkways or driveways instead of soil, concrete or cement surfaces.
  • Photo of porous cement #1Porous cement can be used for sidewalks or driveways and allows water to drain to the underlying soil below.
  • Photo of porous cement #2Porous cement is an open-graded pavement system with small air pockets encased within the pavement.
  • Photo of a detention pond #1Detention ponds are surface water basins that temporarily store rainfall to help prevent flooding.
  • Photo of a detention pond #2They are typically designed to fill up during heavy rain events then drain in between storms.
  • Photo of a media filter #1Media filter systems are filtration systems that use sand or crushed granite to filter out pollutants from rainfall on impervious surfaces.
  • Photo of a media filter #2They can be designed as cartridges in a maintenance hole.
  • Photo of a media filter #3They can also be designed as cartridges in a vault underground.
  • Photo of an oil water separatorOil water separators are designed to separate oil and water. This allows the oil to stay in the system while the clean water discharges. There are two types of oil water separators; the baffle system, called American Petroleum Institute (API), and the coalescing plate system (CP) as shown here.
  • Photo of a detention system #1A detention system is a large pipe or vault that holds rainwater on the property and then allows water to flow slowly through a “flow control structure.”
  • Photo of a detention system #2The flow control structure has a small hole at the bottom of the pipe that meters the amount of water that can drain out of the detention system.
  • Photo of a detention system #3You should never enter a detention system without having had the proper training.
  • Photo of a bioretention system #1Bioretention systems are shallow depressions in the ground with designed soil mix and plants adapted to the local climate and soil conditions.
  • Photo of a bioretention system #2Bioretention systems can be designed to both detain and treat stormwater.
  • Photo of a bioretention system #3They can be used in common landscaped areas at business or residential properties.
  • Photo of a bioretention system #4They are intended to be used in small areas, with no one system larger than 800 square feet of bottom area.
  • Photo of a bioretention system #5They can be designed to take rainwater from rooftops, driveways or parking areas.
  • Photo of a bioretention system #6Green roofs are living vegetation systems installed on top of buildings to slow the flow of stormwater via soil storage, evaporation and transpiration. Green roofs consist of several layers of material to achieve the desired vegetative cover and drainage requirement.

 

Stormwater Systems and Maintenance

Stormwater systems are structures such as vaults, rain gardens, permeable pavements and infiltration systems that provide water quality treatment and/or slow down stormwater flow from impervious surfaces like rooftops, driveways or walkways.

As the owner of a stormwater system, you are responsible for ensuring that the system is operating properly in accordance to the Seattle Stormwater code. Seattle Public Utilities (SPU) may conduct on-site inspections to verify that your facility is functioning and maintained in order for you to receive or continue to receive credit.

Learn more about:

  • Photo of vehicle surfaces #1The impervious surfaces on a parcel are the hard cement or concrete surfaces that do not absorb rainfall during a rain event.
  • Photo of vehicle surfaces #2Stormwater flows off these surfaces into nearby catch basins, then into the property's stormwater structure before discharging into the City stormwater system.
  • Photo of vehicle surfaces #3Such surfaces include parking lots, driveways or parking garage entrances and exits.
  • Photo of building rooftops #1Another type of impervious surface is roof top areas of buildings.
  • Photo of building rooftops #2Rainfall drains off the roof into downspouts on the building and then into nearby catch basins or into the property's stormwater structures.
  • Photo of impervious surfaces #1Walkways, stairs and areas outside doorways are other areas where impervious surfaces can be found.
  • Photo of impervious surfaces #2Cement and/or concrete areas outside buildings are another type of impervious surface that can drain into the stormwater system.
  • Photo of impervious surfaces #3Catch basins located on walkways can also drain into the stormwater systems on the property.
  • Photo of impervious surfaces #4Stairs are another impervious surface type.

 

Single-Family Homes

Typically, single-family homes do not have stormwater systems that qualify for the Stormwater Facility Credit program. But you can still help improve water quality by installing green stormwater infrastructures. For information and technical assistance in installing green stormwater infrastructure on your property.