The goal of this study is to develop recommendations for a statewide, high-performance bioretention soil media (BSM) specification that: 1) reduces contaminant flushing; 2) meets Ecology treatment objectives for total suspended solids, dissolved copper and zinc, and phosphorus; 3) grows plants; 4) is affordable and available; and 5) minimizes toxicity to aquatic organisms. This study tests individual media components for potential contaminant export and sorption capability, and media blends for hydraulic conductivity and plant fecundity.