Notes
This document outlines the Washington State Department of Ecology’s presumed position on stormwater mixing zones, covering when stormwater becomes water of the state, design storm approaches for acute and chronic zones, critical receiving water conditions, and background concentration considerations. It also addresses circumstances under which mixing zone size criteria exceedances may be allowed, referencing WAC 173-201A-100. Handwritten notes at the bottom raise questions about approximating storm events and receiving water flows.
