Bioretention effectiveness for 6PPD and PFAS

King County, in collaboration with Whatcom County, is testing the potential for High Performance Bioretention Soil Media (HPBSM) to reduce contaminants of emerging concern, including 6PPD-q and PFAS, and aquatic toxicity in stormwater. This research is crucial for validating how effective HPBSM is in real-world conditions. Also, this research builds on the findings from a previous laboratory-based SAM study showing that filtration through bioretention reduces stormwater toxicity and protects sensitive fish, like coho salmon (see factsheet).

This SAM study at the Geneva Bioretention Pilot Project location will leverage samples already being collected as part of an existing study to analyze additional parameters including 6PPD-q, PFAS, PAHs, metals, and DOC.

Study questions

  • Does a bioretention facility with HPBSM reduce 6PPD-q and PFAS concentrations in road runoff?
  • Does a bioretention facility with HPBSM reduce the toxicity of road runoff to aquatic organisms?

Study findings

This project will continue through November 2025.

Project tasks & key deliverables

Contract & Scope of Work

  1. Project Management
    • List of TAC members 
    • Semi-annual progress reports
  2. Study Design
    • Quality Assurance Project Plan Addendum
  3. Field Sampling and Laboratory Analysis
    • Lab results from chemical analyses and toxicity testing
    • Field sampling summary memo
  4. Summary Analysis & Report
    • Draft Report
    • Final Report
  5. Distribution of Findings
    • Data formatted for International BMP database
    • Stormwater Work Group Presentation
    • SAM Fact Sheet