Portland UG Network Willamette River Junction
Portland, Ore.
BEST PROJECT
Presented by Michels Corp.
owner PacificCorp
Leading design company AECOM
General Contractor Michels Pacific Energy Inc.
Subcontractor without trenches Michels Corp.
As part of the EPA Harbor Superfund Mile 11 cleanup initiative, the project team installed two parallel horizontal directional drills under Portland’s Willamette River. The scope called for replacing electrical circuits originally laid in the river bed and drilling to depths of 253 feet below the river’s water level while navigating extreme urban constraints and complex geology.
Both drills crossed an existing 14-foot combined sewer tunnel, with HDD-2 maintaining only 10.9 feet of clearance. Although industry standards specify 15-foot spacing for parallel drills, the team stacked holes vertically on the east side and spaced them just 5 feet to the west, passing through a narrow 29-foot easement between deep foundation piles.
Photo courtesy of Michels Corp.
Geologic challenges include contaminated fill, alluvium, cobbles, and boulders that extend 194 feet deep. The team employed innovative telescopic surface casing systems, which combined pneumatic pipe impact with retractable Direct Pipe technology to advance through unstable formations.
Photo courtesy of Michels Corp.
During the installation of the electrical conduit, which required a 500-foot bend radius, the entry point would exceed it, so the team developed an alternative that mitigated the challenges. The 48 inch one. The casing was cut prior to pipe pulling operations and a 500-foot-radius bend was welded to the end of the pipe string. This overbend was then stretched 24 linear feet below the surface, which accommodated the conduit radius requirements and reduced the excavation depth.
