Support for Excavation

Staff | September 28, 2010

DBM Contractors Inc. has recently completed the excavation support for the 1918 Eighth office tower on the corner of 8th Avenue and Virginia Street in Seattle.

The $4.2-million project involved 10,055 lineal feet of drilling to install 124 soldier piles up to 89 feet long. The team also drilled 479 tiebacks up to 100 feet long, totaling 31,500 lineal feet, and installed treated wood lagging to provide 46,000 square feet of shored area.

The site was challenging as crews could only access it from 8th Avenue. In addition, without an easement from the neighboring property, an inner and an outer shoring wall on the east side had to be connected with 10 each 18-inch-diameter pipe rakers and associated walers, further limiting the small footprint of this deep excavation. Fabricated tie-rod walers were also used to connect to previously installed tie-rods from an adjacent shoring project.

Shoring was finished in March 2008, and the building is slated to open in 2009. When complete, the 36-story 1918 Eighth Avenue office building will provide 650,000 square feet of office space, as well as ground floor retail, six levels of underground parking and an outdoor plaza. The building is owned by Schnitzer West LLC and designed by NBBJ. DCI Engineers provided structural engineering, and MKA is the civil engineer. Excavation support system was designed by Ground Support PLLC. The general contractor on the project is Sellen Construction.

DBM also recently completed a sculpted retaining wall at the Bonney Lake (WA) Marketplace. The project involved furnishing and installing 786 soil nails ranging in length from 10 feet to 29 feet; 29,568 square feet of 4-inch temporary reinforced shotcrete facing; and coordinating installation of permanent 8-inch reinforced shotcrete facing with a sculpted architectural finish.

The $1.3-million sculpted wall is designed to resemble natural granite formations and serves as both an aesthetically pleasing design feature, as well as an expansive retaining wall to facilitate the construction of a new Lowes and other retail outlets at the intersection of Highway 410 and South Prairie Road. Construction of the retaining wall ran from October 2007 to December 2007, with the construction of the retail portion of the project scheduled for late this spring. The general contractor on the project is Sierra Construction Company, excavation was done by Donovan Excavating, and the permanent carved shotcrete was completed by Johnson Western Gunite and Turnstone Construction.

Founded in 1949, DBM Contractors Inc. concentrates in specialty geotechnical construction and design/build heavy civil construction, emphasizing drilled foundation support, earth retention, slope stabilization, ground improvement and dewatering. DBM is headquartered in Federal Way, WA, with regional offices in California. The company works on projects throughout the western United States, including Hawaii and Alaska.