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?
  • Scope of Work and Amendment 1

Key Study Deliverables