1101 Dexter Ave N, Seattle, WA (2008)

Shoring System: Temporary Passive and Prestressed Soil Nails with Vertical Elements

Client: Malcolm Drilling Company Inc.

General Contractor: JTM Construction Inc.

Shoring Contractor: Malcolm Drilling Company Inc.

Shoring Face Area: 34,760 Square Feet

Wall Depth Range: 27 to 68 feet

Status: Completed 2008

The project involved the construction of a new 68-ft deep parking garage for a new mixed-use tower, with a three-sided excavation immediately adjacent to SR 99 Aurora Avenue to the west, a highly critical arterial for commute into Seattle from the north. Soils included stiff to hard clays throughout most of the depth, that are prone to raveling and blocky fallout at the face, so that full-height vertical elements were employed. A new condominium tower 10-ft behind the south wall of the project led the team to utilize prestressed soil nails along the south wall. Movements of the south wall were less than a 1/4 of an inch, while the remainder of the walls moved less than 3/4 of an inch. Construction proceeded rapidly and at a much reduced shoring cost compared to conventional shoring due to the design-build solution implemented by the construction team of JTM Construction and Malcolm Drilling, with Ground Support as shoring engineer.