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 on-going until April 2022.

Project tasks and deliverables

Scope of Work

Task 1: Project planning and QAPP development

Deliverable 1.1 Technical Advisory Committee project kickoff meeting notes
Deliverable 1.2 Draft Quality Assurance Project Plan (QAPP)
Deliverable 1.3 Final QAPP

Task 2: Installation and startup

Deliverable 2.1 Table of equipment purchases, and dates received
Deliverable 2.2 Installation photolog
Deliverable 2.3 Installation and Startup Report

Task 3: Monitoring study implementation

Deliverable 3.1 Progress Report #1 summarizing vegetation establishment, water quality event #1, special testing event #1, and O&M observations
Deliverable 3.2 Progress Report #2 summarizing water quality event #2 and O&M observations
Deliverable 3.3 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

Deliverable 5.1 Interim presentation to TAC of draft findings
Deliverable 5.2 Revised analysis report for TAC

Task 6: Communication (to be added to scope of work via amendment)

Contact information

Keunyea Song
Stormwater Action Monitoring Scientist
keunyea.song@ecy.wa.gov

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