Several sites in the Seattle area of Washington incorporated ground improvement as liquefaction mitigation or to increase bearing capacity prior to the 2001 Nisqually earthquake. Facilities with improved ground include an earthen dam, a waste repository embankment, lightweight and large plan structures, and bridge columns and approaches. The sites were improved using vibro-replacement stone columns, vibroflotation, or deep dynamic compaction. All sites performed extremely well, despite evidence of liquefaction and minor structural damage nearby. In this paper, 10 sites are summarized, and the performance of three sites located near liquefied or damaged areas will be described in detail. The detailed sites include a large plan commercial property on liquefiable fill improved to a limited lateral extent, a lightweight tilt-up structure located near evidence of liquefaction at King County International Airport, and an earthen dam with its toe retrofitted using vibro-replacement stone columns
