Seattle— DBM Contactors Inc. is completing a $4.2-million excavation support system for the West 8th Office Building located between Westlake Avenue and Virginia Street on 8th Avenue in Seattle.

The 5.5-month project required installing 111 soldier piles to depths up to 105 feet and 668 tiebacks to depths up to 90 feet. To avoid conflict with deep utilities and subsequent rows of tiebacks, 69 tiebacks were installed at a steep declination angle on waler beams. The entire shoring area is 57,000 square feet with excavation depth of 77 feet in the deepest corner.

West 8th is a 500,000-square-foot, 28-story, Class A office building in the Denny Triangle neighborhood. The building sits atop five levels of underground tenant parking and features two levels of visitor parking as well as street-level retail.

Project team members include owner/developer Touchstone Corporation, architect Callison Architecture, general contractor Lease Crutcher Lewis, and earth retention system designer Ground Support PLLC. The project is scheduled for completion in early 2009.

DBM also recently completed temporary excavation support for the addition of Swedish Orthopedic Institute at 747 Broadway Avenue in Seattle for general contractor Sellen Construction, drilled shaft foundations at the 48th and Pacific section of I-5 with Kiewit Pacific Construction in Tacoma, and two projects in California.