Stabilizing a quarry where rockfalls threatened to crush critical infrastructure under construction demanded a meticulous approach and required workers to rappel slopes to remove loose material. At a cost of less than $500,000, the design-build project involved an outer highwall corner stabilization for a primary crusher station, mitigating rockfall along the conveyor near the highwall and the installation of six micropile caps to structurally support the dump ramp deck.

In the highwall corner, a bench collapse led to a significant slab breakdown and smaller block failures. A combination of the rock mass jointing and the ripple effect of heavy joint structures created poor conditions that required the team to use rock bolts and a reinforced layer of shotcrete to reinforce the area. In the second area, where rockfalls had occurred over the last year on a 900-ft slope near the future conveyor, crews used scaling techniques to remove loose debris and install rock anchors for additional support, a particular challenge considering work in the upper crest area was constrained. Crews successfully coordinated to stay safe.

Building a technically complex retaining wall with a mid-hill foundation on budget and on schedule in two months with zero lost time incidents and no OSHA recordable accidents impressed the judges. “The safety record was perfect for something that had a potential to go wrong in safety,” one judge noted. “This is where the risk is.”

Jeff Segar, chief geostructural engineer at GeoStabilization International, says his firm’s role went beyond the structural design solution for their cantilever deck footing. “We crafted interventions that not only enhanced the project success but preserved a design that could not have been implemented without our expertise and limited access crews,” he says.