When Crux first began installing micro-piles in 2002, the company was already known for providing difficult-access geotechnical exploration services throughout the western United States for tunnel, dam, highway and slope stabilization projects, including the Hoover Dam Bypass. Crux initially utilized micropiles for structure foundation support and slope stabilization before adapting the technology as a foundation alternative in the electrical transmission market. Micropiles provide the ability to install a high capacity deep foundation system in remote or environmentally sensitive locations, says Scott Tunison, Crux’s vice president of operations. “Micropiles are replacement piles constructed using high-strength grout and steel, and can be installed using lightweight equipment,” he explained. In 2004, Crux began construction on the 57-mile-long Swan Lake-Lake Tyee Intertie between two hydroelectric projects in Southeast Alaska. This was the first project of its magnitude to use helicopter-supported micropile foundations exclusively for its whole alignment, relying on Crux’s customized drills, skilled helicopter support and specially trained drillers.
“There was no road access and no development for miles, so custom barge camps were used as mobile living quarters, machine shops, helicopter landing zones and whatever else was needed,” Tunison recalled. “Between access restrictions and the tight window we had to complete foundation work, this was an extremely challenging project. It’s what really launched us into the transmission market.” Crux grew steadily within this market, and now provides design-build foundation solutions for lattice, self-supporting single shaft and guyed transmission tower foundations located in remote areas, or where geotechnical conditions present a challenge to conventional foundation construction. Landmark projects include installing the first micropile foundations for lattice towers on Southern California Edison’s Tehachapi Renewable Transmission Project in 2007, and implementing Crux’s patented steel micropile cap design on San Diego Gas & Electric’s Sunrise Powerlink Project in 2012. Depending on site conditions, micro-pile foundations might be beneficial for an entire alignment, or for just a handful of structures located in particularly challenging terrain. Their lightweight elements and the smaller, lighter equipment required for installation can be transported by helicopter, allowing for construction in areas where road access is not permitted or feasible. Micropiles can also be beneficial when subsurface conditions are challenging or unknown. The threaded sections of casing and high-strength rebar can be adjusted onsite quickly and easily, so the length of the micropiles can be increased in softer-than-expected soils to achieve higher capacity without having to redesign or bring in different equipment. They can also be tested to validate designs, improving efficiency while maintaining safety.
“The projects we go after involve limited-access or challenging sub-surface conditions, and there isn’t typically equipment available on the open market that can do the work exactly as we’d like to do it,” said Tunison. “Ever since Crux was founded, we’ve taken an active role in being innovative, building almost all of our equipment in-house or taking existing technology and evolving it to support our needs.” Crux’s in-house fabrication shop maintains the company’s equipment fleet and designs, and its manufacturing division, Inland Pacific Drill Supply, fabricates and provides threaded tubular steel products.
– Scott Tunison, Vice President of Operations, Crux Subsurface, Inc.