Unpiloted Systems
A Slippery Slope of Opportunity: Bulson Surveying Puts Remote Monitoring to the Test in Telluride
By Rowland Chen
The Telluride–Mountain Village Gondola is a free public, wind- powered transportation system that stretches between the mountain communities of Telluride and Mountain Village, Colorado. Managed by the Telluride Mountain Village Owners Association (TMVOA), this impressive four-station transport system provides some thousands of visitors and residents access to mountain hiking and biking trails in the summer and ski slopes in the winter. Heavy 2023 spring rains caused a significant release of soils from the hillside around Gondola Station 4 in Village Center. An assessment by geotechnical engineers indicated the slope instability was due to subsurface soil movement atop bedrock, a consequence of warming temperatures, melting snow and rain. The area of concern is roughly 2,500 square feet with an average depth of 5 feet [Figure 1]. According to TMVOA, crews removed around 1,270 cubic yards of dirt from the hillside as a precautionary measure to prevent soil from sloughing off the bedrock layer underneath and potentially sliding into the gondola station or the path of the gondola operating line. Of note, the integrity of the gondola station and gondola towers were not threatened by the incident. However, at the recommendation of geotechnical experts, TMVOA contracted Telluride-based firm Bulson Surveying to set up a monitoring regime to scientifically track soil movements in the area over the course of six months. For Dave Bulson, owner of the survey firm, this project was a unique opportunity to demonstrate the power of today’s latest monitoring technology. Remote Reliance The goal of the monitoring campaign around Gondola Station 4 was to track ground movement across the entire area, with particular emphasis
Figure 1 | Soil movement following spring rains around Gondola Station 4
on the hillside retaining wall and around the gondola towers. Per the geotechnical consultant’s requirements, Bulson would need to track and check slope changes daily. “We already had the equipment to effectively monitor a site this size. Our second Trimble S7 total station along with prisms are purpose-built for this kind of activity. Further, I had seen the Trimble 4D Control software at Trimble Dimensions and thought it would be ideal for this monitoring effort.” He called his Trimble dealer, invested in Trimble 4D Control (T4D), and after some training from the Trimble team, was ready to set up the monitoring system at the gondola station. The Bulson team mounted the S7 total station on the gondola station’s steel platform about 10 feet off the ground. The total station was connected to a Settop M1 monitoring controller that relays measurement data to the office. Then, they set 23 prisms along the slope, the retaining wall and the gondola towers (Figure 2). The S7 was set to collect data in 10-minute intervals (6 minutes to scan the prisms, 4 minute rest), 24 hours a day.
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csengineermag.com
Summer 2024
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