Seattle Seawall Historic, Seismic, and Operational Challenges in Concert with Habitat Improvements

Built in the 1930s to improve shipping transportation, the Seattle seawall had deteriorated and needed reconstruction in many places. The city of Seattle Department of Transportation’s (SDOT) Elliott Bay Seawall Project (EBSP) replaced the south half of the seawall adjacent to State Route 99. This required extensive ground improvement to achieve seismic performance requirements and maintain current functions (active piers, utilities, adjacent roadway). The north seawall end is far from SR-99, but still required seismic upgrades to achieve city seismic performance requirements and protect Olympic Sculpture Park (OSP) and the railroad near the seawall. A rock buttress was used at OSP to replace the earth retaining function of the deteriorated seawall, since there are no active piers. This paper provides helpful lessons learned for waterfront planning and design related to historic seawall condition challenges, seismic requirements, and habitat improvements.