Engineers assess the slope daily to determine how deep to excavate and which rock layers to remove. They also track slope movement multiple times each day, relying on new monitoring prisms that have been installed near the rocky outcropping. 

According to Caltrans, it is difficult to define a single representative rate of movement. “Of the 115 prisms onsite, ground surface movements since June have varied daily from 0.005 inch a day to over an inch per day,” a Caltrans spokesperson says. Drone mapping occurs every day when fog and weather conditions allow, and measurement of slope inclinometers is performed several times per week. All monitoring is dependent on cooperative weather, the agency states.  

In late October, crews with Papich Construction—recently acquired by Granite Construction—began installing the permanent cable-net drapery system that is designed to extend from the upper stabilization zone and drape down the face of the slope toward the roadside. It is anchored by steel bars grounded in place or flexible cable anchors along the top of the slope. When the approximately 160,000-sq-ft of high-tensile wire mesh netting is fully installed, it will cover the primary slide area and provide long-term surface protection. The total coverage area may change as engineers confirm final dimensions as the installation progresses and slope contours are finalized. 

Workers continued excavation throughout the summer and fall in phased sections. As the slope was exposed, Caltrans refined the depth and areas of rock removal based on ongoing geotechnical evaluations. The agency said those efforts ensured that crews could reach competent, stable rock before final stabilization measures were installed. In certain areas, Caltrans continued to use Caterpillar Inc. remote-controlled equipment to maintain worker safety where slope stability or access was limited. 

A key component of that slope stabilization is installation of shear dowels that began early this year. By mid-June, 750 shear dowels had been installed but that number grew to a total of 4,691 by early November. That phase is deemed complete, according to the agency.

Caltrans remains optimistic the slide area can reopen by late March but acknowledges that long-range weather issues could impact the opening date.