Notes
Exhibit AR024606, filed in PCHB Third Runway EIS proceedings, discusses points of compliance for stormwater discharges to surface waters under Washington State water quality standards (Chapter 173-201A WAC) and AKART requirements. Document identifies four problems: defining the discharge location as the point of compliance, the absence of an Ecology-approved design storm for mixing zone sizing, lack of formalized criteria for expanded mixing zones for storms exceeding the approved design storm, and unestablished critical receiving water conditions for stormwater discharges. Provides four example situations covering urban storm sewers, private-property ditches, mixed closed-pipe and natural-channel systems, and roadside drainage ditches discharging to naturally-occurring or man-altered streams, impoundments, estuaries, or marine waters. Discusses prerequisites for mixing zone establishment including habitat loss, ecosystem damage, and public health under WAC 173-201A, and addresses beneficial use classifications including drainage uses.