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.
Study question
- Are bioretention facilities being built across Western Washington as designed?
- Once built, are bioretention facilities performing hydrologically as modeled by the Western Washington Hydrology Model?
Study goal
This study led by the City of Olympia will select 10 new bioretention sites that were built to the 2012 or later manual design.
Results of the project will provide data to evaluate design and performance, and confidence in how the the 2012 (current) bioretention design performs hydrologically.
Project tasks and deliverables
Scope of work, Amendment 1
Tasks
Task 1: Project Management
- D1.1 Quarterly Progress Reports
Task 2: Site Selection and Preparation
Task 3: Develop Quality Assurance Project Plan (QAPP)
Task 4: Study Monitoring
Task 5: Data Analysis and Modeling
- D5.1 Meeting with SWG
- D5.2 Technical memo on models for each site
- D5.3 WWHM model of each site
- D5.4 Memo of interim findings for SWG
- D5.5 Meeting with SWG on interim findings
Task 6: Report & Findings Communications
- D6.1 Draft report for review
- D6.2 Presentation
- D6.3 Final report
- D6.4 Fact Sheet
- D6.5 Presentations to counties and cities (to be decided- ideas below)
- north, south, central, east or west sound locations
- southwest WA
- local conferences