Green Stormwater Infrastructure

Green Stormwater Infrastructure

Green Stormwater Infrastructure was piloted in the Broadview neighborhood in northwest Seattle.


Banking on Green, a recent national report, finds that green infrastructure solutions like rain gardens save money and provide community benefits by managing stormwater where it falls. The report was released in April 2012 by the American Society of Landscape Architects (ASLA), American Rivers, the Water Environment Federation (WEF), and ECONorthwest.  

The report’s top findings:

  • Not only does green infrastructure cost less, but these practices can further reduce costs of treating large amounts of polluted runoff.
  • Green infrastructure can help cities reduce energy expenses.
  • Green infrastructure can reduce flooding and related flood damage.
  • Green infrastructure improves public health — it reduces bacteria and pollution in rivers and streams, preventing illnesses in swimmers and boaters.

Seattle has been on the leading edge of Green Stormwater Infrastructure (GSI) for more than a decade. Simply put, it’s using green solutions to help reduce overflows by allowing stormwater to infiltrate slowly into the ground and cutting the volume of stormwater entering the system.

One of the most exciting aspects of Seattle’s 2010 CSO Reduction Plan (pdf) is the chance to pilot green solutions to reduce the amount of stormwater that enters the sewer system in the first place.

In a nutshell, the goal is to use green solutions to the maximum extent feasible to reduce CSOs. Green solutions control the sources of pollution by slowing, detaining, or retaining stormwater so that it does not carry runoff into nearby waterways. This reduces the volume and timing of flows into the system.

View a presentation about GSI for CSO reduction (pdf)

Seattle has experience with this approach through previous natural drainage projects and we will learn even more from the Ballard Natural Drainage, designed to replace hard surfaces with natural drainage areas that allow stormwater to gradually seep into the ground.

Green solutions won’t work in all areas because of Seattle’s hilly topography, the width of certain streets, and soil conditions, among other factors. GSI projects are anticipated in these drainage basins (pdf):

  • Windermere
  • Fremont/Wallingford
  • North Union Bay
  • Montlake
  • Interbay
  • Genesee
  • Henderson 

Seattle has also established RainWise to inform homeowners and businesses how to install GSI on their own properties.