Expert testifies bioretention likely removes 6PPD-derived toxin but long-term efficacy uncertain

At a Feb. 10 hearing before Kitsap County Hearing Examiner Phil Albrecht, consultant witness Mr. Kindred said laboratory and field studies indicate that bioretention soils and engineered media can remove 6PPD-quinone — the tire-derived oxidation product tied to salmon mortality — from stormwater effluent.

The comment matters because the Meadowview preliminary plat will discharge treated runoff to a buffer and Barker Creek; opponents had cited Ecology guidance urging further study of 6PPD and road runoff.

Kindred, who described a career studying fate and transport of chemicals in the subsurface, told the examiner that early experiments exposing coho salmon to untreated freeway runoff showed nearly 100% pre-spawn mortality and that treating that runoff through bioretention media produced…