A 1993 Port of Seattle letter to Des Moines resident Barbara Stuhring explains that airplane deicing at Sea-Tac uses only FAA-approved ethylene or propylene glycol, and that wastewater from deicing drains to the airport's treatment system before being discharged to Puget Sound — not to Miller or Des Moines Creeks. A 1996 Final Environmental Impact Statement (EIS) later addressed public concerns about deicing fluid effects on local waterways, concluding that glycol quantities in stormwater runoff were too small and too diluted to cause lethal impacts on aquatic life in those creeks. Stuhring subsequently wrote to the Port challenging what she saw as a contradictory response in the Final EIS compared to the original 1993 letter.Open full document
Notes
A December 1993 letter from the Port of Seattle to Des Moines resident Barbara Stuhring explains that the FAA requires airlines to use only ethylene or propylene glycol for deicing, that deicing areas drain to the airfield wastewater treatment system and discharge to Puget Sound (not Des Moines or Miller’s Creeks), and that the Port’s treatment plant is not designed to treat glycols. The document also includes a follow-up letter from Stuhring to the Port dated March 1996 challenging statements in the Final EIS that she believed contradicted the 1993 letter, as well as an excerpt from the Sea-Tac Airport Master Plan Update Final EIS addressing comments about deicing fluid impacts on Miller and Des Moines Creeks.