Washington State University - Puyallup will be evaluating a water flow rate controlling outlet (called an orifice) which is part of a bioretention underdrain system. The project will be studying bioretention facilities with smaller orifices controlling the water flow rate and evaluating both water quality and water quantity performance improvements.
Study questions
- What is the water quality treatment performance of bioretention with the smaller outlet-control as compared to the traditional media-controlled configuration?
- How does outlet-control vs. media-control effect the residence time and residence time distribution of water in the bioretention mesocosm?
- Are any differences in plant health and vigor notable at a mesocosm scale between outlet-controlled and media-controlled designs?
- Does a small orifice pose notable operations and maintenance issues compared to standard bioretention BMPs without underdrain outlet controls?
- How are the hydraulic conditions (i.e., stage-discharge relationships) of the compared systems different? Any impacts to modeling?
- How do hydraulic conditions vary over time and between replicate mesocosms?
Study findings
This study is on-going until April 2022.
Project tasks and deliverables
Scope of Work
Task 1: Project planning and QAPP development
Task 2: Installation and startup
Task 3: Monitoring study implementation
- Progress Report #1 summarizing vegetation establishment, water quality event #1, special testing event #1, and O&M observations
- Progress Report #2 summarizing water quality event #2 and O&M observations
- Progress Report #3 summarizing water quality event #3, special testing event #2, and O&M observations
Task 4: Modeling study (to be added to scope of work via amendment)
Task 5: Reporting and communication of findings
- Interim presentation to TAC of draft findings
- Revised analysis report for TAC
Task 6: Communication (to be added to scope of work via amendment)