Confidential Transmission Line Rebuild Program

A large utility owner is replacing ten miles of transmission structures along a 100-year-old service line. The transmission line alignment parallels the James River and crosses very rugged terrain for five miles before crossing the river and continuing to the south. Much of the alignment is located within United States Forest Service (USFS) land with mountainous terrain, making it difficult to mobilize large, drilled shaft rigs and concrete trucks to the structure locations.

Schnabel evaluated the site conditions, developed and executed a subsurface exploration program to gather subsurface information along the transmission line alignment, and prepared a geotechnical engineering report with our recommendations regarding foundations for the proposed transmission and substation structures. Schnabel continuously consulted with the owner throughout the life of the project to inform them of progress, discuss site conditions, consider multiple foundation types, and determine the appropriate foundation system at each structure location. The result was a combination of drilled shafts and prefabricated steel grillages supported on micropiles. The micropile equipment was much smaller and on tracks, so the equipment could access the remote structure locations on narrow paths through the woods. Schnabel performed the subsurface exploration and geotechnical engineering study for the transmission and substation structures, performed micropile load testing, designed the micropile foundation system for the structures, designed the retaining walls for the substation, and designed the gabion embankment for access across a ravine.