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 underway

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

The City of Bellingham is leading the evaluation of older bioretention facilities, those built before the 2012 design standard.
The City of Olympia is leading the project to evaluate facilities built to 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.

Pre-2012 Bioretention Hydrology Performance Study

Study questions

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 findings

The City of Bellingham is leading this effort to evaluate 10 early design bioretention facilities against model predictions. Ten sites were monitored in the winter of 2016-2017, and represent real-world early design bioretention facilities and conditions.

The results evaluate hydrologic performance of the built facilities and provide reasons and data for observed differences. A final report is expected in late 2018.

Project tasks and deliverables

Project tasks

Project management and formation of a technical committee; quarterly progress reports (Deliverable 1.1)
- Q4 2015
- Q1 2016
- Q2 2016
- Q3 2016
- Q4 2016
- Q1 2017 – Progress Report
- Q2 2017 – Progress Report
- Q3 2017 – Progress Report
- Q4 2017 – Progress Report
- Q1 2018 – Progress Report
Site selection criteria and list of sites
- Deliverable 2.1
- Deliverables 2.2-2.3
QAPP (Quality Assurance Project Plan)
- Deliverable 3.1
- Deliverable 3.2 – Final Quality Assurance Project Plan
Monitoring implementation; equipment and initial site reviews
- Deliverable 4.1
- Deliverable 4.2
- Deliverable 4.3
- Deliverable 4.4
- Deliverable 4.5
- Deliverable 4.6
- Deliverable 4.7
Data analysis and committee review of interim results
- Deliverable 5.1 – Effectiveness study PowerPoint presentation
- Deliverable 5.2
- Deliverable 5.3
- Deliverable 5.4
Draft report, presentation, final report, and fact sheet
- Deliverable 6.1
- Deliverable 6.2
- Deliverable 6.3
- Deliverable 6.4

Current Design Bioretention Hydrology Performance Study

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

Contact information

Brandi Lubliner
Stormwater Action Monitoring Coordinator
brandi.lubliner@ecy.wa.gov
360-407-7140