The project involved swapping transmission line positions between the Eldorado-Mohave and the Eldorado-Moenkopi 500 kV transmission lines, located outside Boulder City, NV. This included installation of two replacement structures on the Mohave line and one on the Moenkopi line.
Southern California Edison, Wilson Construction, Crux Subsurface
Three of the four replacement structures featured difficult access and shallow hard rock, requiring a foundation alternative to drilled shafts. Crux designed and constructed concrete cap micropile foundations at these locations. A combination of forklift and low-pressure carriers were used to access the steep, rugged terrain, and Crux’s patented micropile drills were set on drill platforms at each tower leg. In total, 48 piles and over 1500 feet of drilling were successfully completed under in-service overhead lines.
Excavation in shallow rock and on steep slopes was highly challenging. Top of concrete elevations were fixed by the owner, requiring crews to work through the challenges without the option to redesign. Excavation work was successfully completed using compact, remote excavators, followed by foundation drilling and concrete placement.
Additional project challenges included working within the protected Desert Tortoise habitat. Associated environmental restrictions required biological escorts for all crews working on the right-of-way or onsite.