Notes
WSP USA memorandum dated June 10, 2025, from Dan Roscoe (WSP) to Adele Pozzuto (Port of Seattle) verifying the 2022 wetland delineation for the Seattle-Tacoma International Airport (SEA) Industrial Wastewater Treatment Plant (IWTP) Expansion Project. The verification covers two study areas — AGB Study Area and Lagoon 3 Study Area — and confirms three previously delineated wetlands (IWS-A, IWS-B, WL28) located within the Lagoon 3 Study Area. Methods follow the Corps of Engineers Wetlands Delineation Manual (1987) and the USACE WMVC Regional Supplement (2010). Wetlands include Palustrine Forested (PFO) and Palustrine Scrub-Shrub (PSS) depressional types rated Category I and III under Washington State Ecology and City of SeaTac criteria, with buffer widths of 60–165 feet. The 2022 delineation was originally conducted by Anchor QEA for the Snow Storage Expansion Project. City of SeaTac Critical Areas Code revisions anticipated 2025–2026 may affect buffer requirements.