Orifice control of bioretention

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 ongoing until December 2022.

Project tasks and deliverables

Scope of Work, Amendment 1, Amendment 2

Task 1: Project planning and QAPP development

Task 2: Installation and startup

Installation and Startup Report

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
Progress Report #4 summarizing water quality event #4, and O&M observations
Progress Report #5 summarizing water quality event #5, special testing event #3, and O&M observations
Progress Report #6 summarizing water quality event #6, and O&M observations

Task 4: Modeling study

Modeling Study Plan
Draft modeling study report
Final modeling study report

Task 5: Reporting and communication of findings

Interim presentation, Interim presentation#2 to Stormwater Workgroup and Technical Advisory Group
Final presentation to Stormwater Workgroup
Final report
Data submittal to Ecology
Factsheet

Contact information

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

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