Rainier Square in downtown Seattle spans nearly an entire city block and currently houses the iconic Rainier Tower, designed by Minoru Yamasaki, the architect of the World Trade Center. To complete Rainier Square, a 58-story mixed-use skyscraper is under construction, right next to the 40-year-old Rainier Tower. At a towering height of 850 feet, this new structure will become the second tallest building in Seattle.
Foundation excavation will reach 87 feet below the Rainier Tower’s foundation, and it will entail 85,000 square feet of soldier beam shoring along with tie-backs that extend over 135 feet. The soil conditions encompass 15 feet of fill atop 30 feet of silty sand and 50 to 60 feet of clay with slickenside features, which result from the nearby Seattle fault zone and glacial till. In the areas of deepest excavation, a secant pile shoring wall with tie-backs has been selected to address potential settlement concerns near Rainier Tower.