This document summarizes the environmental wetland impacts associated with airport expansion projects near Sea-Tac Airport, detailing acreage affected across four creek basins — Miller Creek, Walker Creek, Des Moines Creek, and Green River. It breaks down impacts by wetland vegetation type (forested, shrub, emergent, and open water) and hydrological classification (depressional, riverine, and slope), with total impacts ranging from 4% of the Walker Creek project area to 100% of the Green River area. The tables also distinguish between temporary and permanent wetland impacts as determined by the U.S. Army Corps of Engineers, covering features such as the Third Runway and Runway Safety Area extensions.Open full document
Notes
This document presents three tables summarizing wetland impacts associated with an airport project across four creek basins: Miller Creek, Walker Creek, Des Moines Creek, and Green River. Table 1 details acreage impacted by Cowardin and HGM classification for each basin, Table 2 describes the Corps’ determination of on-site temporary impacts by vegetation type and duration, and Table 3 provides detailed permanent and temporary impact data by wetland, watershed basin, and Cowardin classification.