C+S April 2020 Vol. 6 Issue 4 (web)

well.” The real-time processing of the GNSS data is done by Leica Spider software, and these data are then displayed by GeoMoS Now!, a cloud-based analysis tool. MacIsaac defined the displacement thresh- olds used to automatically generate alert messages that are relied upon by BC MOT and other entities that must safely interact with the slide area and provide guidance to the local homeowners and to the traveling public. The Leica Geosystems monitoring system has been in place for more than a year and has provided an uninterrupted record of displacements from the slide (and at the low millimeter level), supporting the min- istry’s decision to use Leica Geosystems’s expertise, equipment, and software for this demanding task. “System uptime is very important to us and is a big differentiator for our monitoring solutions,” says Rutledge. “Our GM30s have internal memory that can be partitioned so that part of it operates on a first- in first-out basis. That means that even if there is a communication failure, or if the ministry’s server goes down, all of the data collected at that site is available from this partition for a year or so. We automati- cally retrieve it and process it once the system is back online.” A month after the monitoring system was in place, MacIsaac and the MOT geotechnical team concluded that the landslide had stabilized, based upon the GNSS data, and gave the go-ahead to rebuild the Old Fort Road, restore utility service, and end the evacuation order. A Stressful System Test On November 29, 2018, just a few days after residents began to return home, a 4.5 magnitude earthquake was felt over the Peace River region and was particularly noticeable in Old Fort—the earthquake’s epicenter was less than 20 kilometers from the still-recovering town. Residents across Northeast B.C. reported strong tremors that rattled homes and businesses for several seconds. That kind of seismic activity worries

anyone who feels it, but Old Fort residents were understandably more alarmed than most. Had the earthquake triggered a new, massive land- slide event? One that could easily destroy the newly restored access to their little community, forcing another evacuation? “It was a surprise, for sure,” says MacIsaac. “We don’t have a lot of earthquake activity around here. Of course, my first thought was to check on the landslide.” Rutledge, who was in the area, was also concerned. Since the Leica Geosystems monitoring system had been collecting data for some time now, he and MacIsaac were able to log into the GeoMoS Now! website and see what if any displacements it might have triggered. “We looked at it and could verify right away that there was no displacement at all, which was pretty amazing,” says Design was crucial to the success of the system. The monitoring solution had to track the landslide in three dimensions at the millimeter level around the clock and measure the precise displacements in real-time. The innovative monument design is likely to be influential in landslide monitoring projects for years to come.


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