SRP commissioned the project to accommodate the growing mining customer load in the Eastern Mining Area, located east of Phoenix, AZ. New structures and an upgraded line were installed to replace existing infrastructure, originally constructed in the early 1900’s.

Crux provided micropile foundation design-build services to support 63 lattice tower structures and 4 tubular steel poles for the alignment, traversing the rugged terrain of Arizona’s Superstition Mountains. Access varied from highly challenging to completely inaccessible by conventional equipment, and ultimately required helicopter support. Crux utilized custom, lightweight micropile drills placed on adjustable construction platforms to accommodate the steep ground slopes and substantial vertical differentials encountered along the alignment.

Crux completed a geotechnical desktop study using project-specific and publicly available data to develop foundation designs for a range of anticipated geotechnical conditions at each site. Site-specific conditions were confirmed during construction through real-time, on-site geotechnical characterization. In total, 273 piles were installed to depths of up to 60 feet. A minimum of one pile was proof tested at each structure location.

Pre-construction challenges included concerns with the proposed structure to pile connection. Crux and SRP worked to develop a structural steel pile cap that would support the entire structure footprint, providing a robust and secure connection between the superstructure and foundation elements. Additional challenges included effective communication through the mountains and canyons. Repeaters were frequently unreliable, and helicopter was the only method of relaying information. In addition, a landslide cut off access to a portion of the sites, requiring the use of side-by-side vehicles and implementation of additional safety precautions.