Notes
This SEPA environmental checklist prepared by the Port of Seattle describes the IWTP Enhancement Project at Seattle-Tacoma International Airport, which involves upgrading the existing Industrial Wastewater Treatment Plant and constructing a new aerated gravel bed (AGB) treatment facility to handle high-BOD wastewater from aircraft deicing operations. The project is driven by tightening permit conditions from King County and Ecology, which are reducing the allowable daily BOD discharge limits from 60,000 to 12,000 pounds per day. Construction is scheduled to begin in Q2 2026 and be completed by Q2 2030.