Bioretention hydrologic performance studies

Use of bioretention is widespread in the Puget Sound region and expected to increase as a preferred means for stormwater flow control and reducing pollution.

State and local governments are eager to evaluate and ensure that bioretention facilities constructed under Ecology’s Stormwater Management Manual for Western Washington attain the desired performance.


Studies measuring hydrologic control of stormwater

Two projects (phases) of a similar design are currently active to evaluate bioretention facilities built to two different design standards. 

  • Phase I: The early bioretention facilities in western Washington were designed prior to the 2012 stormwater management manual for Western Washington. The City of Bellingham led the first project.
  • Phase II of the project is led by the City of Olympia to evaluate facilities built using the 2012 bioretention design standard.
Both projects will assess performance of the facilities to capture, infiltrate stormwater runoff. Results will be compared to model predictions. The findings will provide feedback on design, construction, maintenance, or modeling that impact the hydrologic performance of bioretention facilities.