Blair Waterway Horizontal Directional Drilling Project

As part of infrastructure improvements to accommodate the next generation of shipping container vessels, the Port of Tacoma, Washington, developed plans to widen and deepen the Blair Waterway shipping channel, situated within the Port’s Industrial Development District. First, however, the Port had to relocate several conflicting utility lines running under the waterway as well as high-voltage transmission power lines running overhead. All of these needed to lie underground beyond the limits of the future channel. The geology consisted of loose sands and silts, making utility excavation a challenge.

Jacobs Associates provided comprehensive engineering services, including detailed design, preparation of plans and specifications, construction scheduling, and cost estimating. We also assisted the Port during bidding and provided engineering assistance during construction.
During preliminary design, we evaluated several methods of tunnel construction. Horizontal directional drilling (HDD) was chosen to install utilities beneath the waterway in four parallel 2,200-foot-long (671 m) crossings. These crossings consisted of a bundle of HDPE conduits installed within a 24-inch (61-cm) HDPE casing pipeline for fiber optic and copper cable communication lines; a 12-inch (30.5-cm) HDPE waterline; a bundle of five 8-inch (20.3-cm) HDPE conduits for 15 kV distribution lines; and a bundle of four 8-inch (20.3-m) HDPE conduits for a 115 kV transmission line. The utilities terminated in vault structures and special termination trenches. 

The project, completed in 2005, involved many challenges, including a fast-track schedule and limited construction space at the Port due to ongoing operations within existing container terminals. The project also involved close coordination with multiple utility owners.