Excavation as defined in Ch 19.122 Revised Code of Washington (RCW), whether by open cut or trenchless technology method, shall not damage underground installations, surface improvements, or adjacent structures. Excavations that are classified as trenches are required to have a safety system (refer to the requirements defined in the Washington State Administrative Code (WAC) 296-155 Part N. Additional requirements for safety systems apply to underground construction refer to the requirements defined in WAC 296-155 Part Q.
Shoring is a means of supporting the earth in a trench or vertical cut for building and roadway construction or other underground installation activities. There are many types of shoring and ground support techniques for earth reinforcement or support of excavations. Properly installed shoring system for excavations is critical for maintaining the structural integrity of the adjacent roadway structures and underground utility infrastructure. The WAC has a number of regulations addressing shoring and excavations that depend on site specific site and subsurface conditions. Refer to the City of Seattle Standard Specification 2-04 for more specific information on general trench shoring requirements, and for trench shoring regarding water mains.
Shoring review, approval and inspection of Utility and Street Improvement Permits are performed by SDOT through the permitting process. During building permit applications, DPD reviews the stability of the adjacent private property while SDOT reviews the plans to ensure stability of the right-of-way. For more information, refer to the Street Use Shoring Review website.