1001 Office Towers, Seattle, WA (2022)

Shoring System: Temporary Soil Nailing

Client: TC Northwest Development, Inc.

General Contractor: Howard S. Wright

Shoring Contractor: Malcolm Drilling Company, Inc 

Shoring Face Area: 96,500 Square Feet

Wall Depth Range: 80 to 96 feet

Status: Completed 2022

The muti-story office tower included 8-9 levels of underground parking with excavation depths extending to 96 feet. Soil conditions consisted of limited depths of fill over glacially overridden till and Advance Outwash sands and gravels, with limited exposures of hard silts near the base of the excavation. Conventional soil nail shoring was used, with limited depth vertical elements as required in specific areas to address underground utilities and potentially unstable fill. Up to 17 rows of nails were installed and maximum deformations of the shoring wall did not exceed 1 inch. This is deepest vertical soil nail wall in the world in an urban environment.