Remote Access Micropile Design-Build
The Columbus/Rapelje-Nye Transmission Line is a new, 53-mile, 115 kV transmission line located in Stillwater County, Montana. The line will connect the existing Columbus-Rapelje Substation to a new substation near Nye, Montana. The line is intended to increase capacity, addressing involuntary load shedding and subsequent outages affecting Stillwater Mine.
Crux was selected to provide foundation design-build services for a three-mile portion of the new line. Due to this portion’s remote location and rugged terrain, conventional access was not permitted, requiring all materials and equipment to be transported using medium and light-lift helicopters. Several options were considered before micropiles were selected as the most efficient option. Micropiles have a high capacity for their size and allowed fewer, but larger structures to be placed compared to other foundation options. Crux completed 20 foundations for 10 H-Frame structures, drilling a total of 74 piles to depths ranging from 23-45 feet.
Prior to beginning construction, a project schedule was developed to work around environmental and weather concerns. The project window was set to avoid fire season, requiring construction to take place while grounds were still frozen. To mitigate the risks associated with this, crews received specialized training for anticipated weather changes and slipping hazards. To avoid temperature-related malfunctions or delays, equipment was properly maintained and stored at the end of each day.
Challenges included working in difficult access locations at high elevations with extreme winds. Due to the rugged and remote terrain, materials and crews were transported by helicopter from a nearby staging yard. To accommodate the high elevation, helicopter weights were reduced for external longline loads. Facing windstorms up to 30 miles per hour, crews took careful consideration to minimize helicopter hours. Working closely with helicopter pilots and taking additional precautions, all foundation work was completed safely and within the project schedule window.