Federal Way-based DBM Contractors, Inc. has completed temporary excavation support for the JCM U-Link Joint Venture at the Sound Transit Link U230 Capitol Hill Station in Seattle. The deep excavation measures 550 feet long by up to 80 feet wide and extends to over 70 feet deep below the adjacent city streets.

The earth retention system required DBM to install 141 each anchored steel temporary soldier piles averaging nearly 100 feet deep, 1,118 each temporary tieback anchors, 363 Double Corrosion Protection (DCP) soil nails plus 11,840 square feet of 8-inch temporary shotcrete facing, 81,270 square feet of treated timber lagging and one row of 6 each 36-inch diameter pipe struts and double wide flange (WF) beam walers for "cross-lot" excavation support and to support the streets and sidewalks of the surrounding city blocks.


Site dewatering was required to facilitate the excavation and was complicated by the fact that the bottom of aquifer on the North end was above the bottom of the excavation. To accomplish the dewatering, DBM installed nine each deep wells and approximately 150 each vacuum wellpoints.

When completed, the deep excavation will provide access for launching the tunnel boring machine (TBM) scheduled to bore twin tunnels to the Pine Street Stub Tunnel, as well as receive a second TBM boring twin tunnels from the University Station. The project is part of the Sound Transit alignment extending to the University of Washington. 

About DBM

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 with regional offices in Capitola and Escondido, California. The company works on projects throughout the western United States including Hawaii and Alaska.