CLIENT: MoTT C/o: Wyssen Avalanche Control Inc.
OVERVIEW:
Eight permanent Wyssen avalanche towers set on steep, rocky terrain above the Trans-Canada Highway at Three Valley Gap. Each tower stands 8 or 10 m tall and leans out over the avalanche initiation zone. A deployment box on each tower holds 12 explosive charges, which are lowered on a cord one at a time and detonated to trigger avalanches remotely.
Four towers were installed in fall 2016, with the remaining four scheduled for 2017.
CHALLENGE:
MoTT needed to run avalanche control on this stretch of highway at any hour and in any weather, so that closures last only as long as the control work itself. That meant permanent structures placed directly in the initiation zone: steep rock that field crews could reach only by rope, with rock fall hazard to manage during construction and over the life of the towers. Each foundation had to carry a tall tower inclined out over the slope.
APPROACH:
PRI carried the work from investigation through construction:
- Site investigations carried out by rope access, providing the ground information for both foundation design and rock fall mitigation.
- Recommendations for rock fall hazard mitigation.
- Geotechnical and structural design of the tower foundations.
- Construction drawings and specifications for the tower foundations and the permanent rock fall protection works.
- The construction environmental plan.
- Coordinating professional services.
- Witnessing of anchor verification testing.
- Sampling and testing of the grout and concrete used in foundation construction.
OUTCOME:
The tower system lets MoTT complete avalanche control in all weather conditions, day or night, rather than waiting for conditions that allow conventional control. The result is a more reliable highway and shorter closures. Every foundation was built against verified anchor tests and tested grout and concrete.