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Regional stormwater facility study in Federal Way

King County is evaluating how effectively a large improvement project treats stormwater at a regional water detention facility in Federal Way. The retrofit includes the addition of two large bioretention cells and an enhanced wet pond.

Study focus

Each individual best management practice (BMP) and combination of BMPs are evaluated for how well it controls water flows and reduces pollution from stormwater. This study also evaluates the instream water quality and benthic macro-invertebrates in North Fork West Hylebos Creek before and after the retrofit.

Study question

The study’s sampling quality assurance project plan provides information on the study design.

  • How well does each individual practice treat stormwater in this large retrofit?
  • What about combinations of treatments?
  • What is the overall flow control and pollutant reduction to the stream?

Study findings

The sampling phase was completed ahead of schedule, in early 2017. The final report is expected in early 2018.

Project tasks and deliverables

  1. Draft and final Quality Assurance Project Plan
  2. Field sampling and analysis and quarterly progress reports
  3. Data analysis progress reports, draft, and final project report
    • Deliverable 3.1
    • Deliverable 3.2
    • Deliverable 3.3
  4. Distribution of findings: EIM, Presentation, BMP database
    • Deliverable 4.1
    • Deliverable 4.2
    • Deliverable 4.3
    • Deliverable 4.4
  5. Project Management: semi-annual overview progress reports
  6. (Conditional) Long detention time sampling; progress reports
    • Deliverable 6.1
    • Deliverable 6.2
    • Deliverable 6.3
    • Deliverable 6.4
    • Deliverable 6.5