By Steve Brushey and Scott Garvin
This article was first published in The Avalanche Journal, Volume 124, Summer 2020
FIFTY-SIX KILOMETRES WEST OF TERRACE along Highway 16, a 400-metre-high granite monolith rises from the banks of the Skeena River amongst a vast expanse of large coastal mountains. The area is home to goats, bats, and various species of birds and frogs. It has shared interests with three First Nations groups and is also one of several locations along the corridor where the highway is located within the CN Rail right of way.
Despite the abundance of precipitation and potential for significant snowfalls in winter, the terrain at 35 Mile doesn’t have the capacity to produce large avalanches (greater than size 2.5) capable of taking out hectares of timber or burying the highway metres deep in dense snow. Instead, 35 Mile is a good example where highway location, type of overhead terrain, avalanche frequency, avalanche terminus, and terrain trap all merge to create a very tight operational risk band that can quickly transition from low to high risk as defined by the Ministry of Transportation and Infrastructure (MoTI) Snow Avalanche Threshold Guidelines.
In 2014, a trial section of avalanche fencing was installed at one of the three avalanche paths at 35 Mile to determine its viability for avalanche mitigation at this location and to ensure the fencing would not create additional hazards, mainly icefall, that could affect the highway. Over the following winters, the MoTI’s Northwest Avalanche Program determined the fencing project was not suitable for the location given the abundance of steep terrain below where the fences could be installed, and the steepness of the terrain in the remaining areas to be mitigated. The search for funds for the completion of the remaining 85% of the fencing project ceased, and research and discussions for more viable options, such as remote avalanche control (RAC) devices, quickly ensued.
PROJECT AND TIMELINE
With the advances in RAC technology and the determination that avalanche fencing was not a suitable mitigation strategy for the terrain at 35 Mile, MoTI hired the engineering firm Stantec to lead the project in the spring of 2018. Their job was to determine a RAC device that would be best suited for the complexity of 35 Mile and the operational challenges of a regional highway forecasting program.
Stantec worked closely with the Northwest Avalanche Program to develop a table of requirements for a RAC system, which was advertised by the provincial government through a request for proposal. The RFP highlighted a need and desire to move away from explosives avalanche control. We did not want a RAC that used explosives as we were too close to the highway, and as a regional program with such a large coverage area, we wouldn’t have the manpower to pre-assemble all the individual charges. We also did not want to have to deal with any sort of explosives-related delays from a misfire. In the end, the TAS’s O’Bellx was chosen as the optimal system.
By August of 2018, all the pieces of the project began to come together. MoTI purchased five O’Bellx units from TAS (through Avatek Mountain Systems Inc), appointed a local MoTI project manager, and retained 6 Point Engineering to assist with specific engineering aspects of the installation. In September of 2018, Axis Mountain Technical Ltd. was awarded the contract to install the O’Bellx units. The units and towers arrived in Terrace in February of 2019 after a long journey from France and were stored for the remainder of the winter, awaiting their planned installation date in May.
The initial set up for the installation process began in late April and site work began in early May. The work progressed relatively quickly, with the tower installation phase of the project wrapped up by mid-June. The final phase, flying the O’Bellx units into place and commissioning each device, was deferred until the fall as commissioning in June would have meant the units would have to be taken down for the rest of the summer and re-deployed in the fall prior to winter start-up. The goal was to deploy the O’Bellx units, test them, and have them remain in place and ready to go for the winter.
After several unavoidable delays in September, commissioning finally took place in early October. Fortunately, the weather cooperated and the O’Bellx deployment went as well as planned. All the units were commissioned and ready for the coming avalanche season by mid October.
FIRST SEASON’S DATA
With our changing climate, winters are seemingly becoming harder to predict and this is even more evident for avalanche areas that exist at lower elevations. As mentioned earlier, 35 Mile rises from near sea level to approximately 400m elevation. The area is subject to heavy precipitation and snowfall rates can exceed four centimetres per hour quite regularly. The weather can often transition from snow to rain during typical southwesterly storm events.
With a new RAC system at our fingertips, we entered the season wondering what winter would bring us. Would we have a mild winter with mostly rain at low elevations, or would snowfall begin in November and seemingly never end until March? The following is a synopsis of the first winter with the O’Bellx units in place:
- Snowfall for the 35 Mile area as a percentage of average:
o December – 100%
o January – 205%
o February – 172% - Avalanche control:
o Six control missions (four nighttime, two daytime)
o 22 O’Bellx shots fired
o 14 avalanches affecting the highway produced - Highway closures
o Six closures for control (the long-term average is three per season)
o A 73% reduction in closure times, with short control missions and no prolonged closures due to high avalanche risk.
HIGHLIGHTS AND IMPROVEMENTS
A direct enhancement from the O’Bellx units was evident from the initial control mission. Previously, avalanche program and maintenance personnel would spend long periods of up to 36 hours monitoring, assessing, and implementing specific safety measures on site until helicopter control work could be completed at daylight, when weather conditions permitted. Or, the highway was closed due to high risk when conditions exceeded the operational risk band.
With the O’Bellx units in place, the crews could set up quickly and return the highway to a safe standard much more efficiently, day or night. Completed control missions by 2 a.m. also meant additional sleep.
Anyone who has deployed explosives charges from a helicopter in confined low elevation terrain and in less than desirable weather conditions will understand our enthusiasm for the O’Bellx system. Eliminating this aspect of the previous avalanche control method at 35 Mile through was overwhelmingly welcomed.
CHALLENGES
The addition of the O’Bellx RAC system has not come without a few challenges. The biggest has been learning how to adapt to the new system’s capabilities and how to change the approach to mitigation when you have been doing it differently for roughly 20 years.
The “grabber” device supplied by TAS for deploying and retrieving the O’Bellx units from the towers by helicopter had some intermittent mechanical issues that were originally identified by other TAS clients in the United States. The units can be deployed by standard long line process and this was the method we used while TAS sorted out the grabber issue.
It was resolved by the end of the winter and the necessary upgrade were made to our device. It was used for retrieving the O’Bellx units off their towers in the spring for summer maintenance and storage with no significant issues. There were several times during the multi-sync firing sequence (multiple O’Bbellx units firing simultaneously) that one of the units dropped communication and did not fire. TAS updated the UHF radio antennas with the hardware for our vehicles, along with a software update, which appears to have remedied the communication problem.
There were two occasions where there was some discrepancy in the software data outputs for the O’Bellx units during the firing sequence as compared with the acoustic confirmations. Again, this appears to have been remedied by the recent software update from TAS, but we will have to confirm next season.
LEARNING OUTCOMES
2019-20 was the first winter of use for the O’Bellx. Given this was the first installation of its kind in Canada and a first for using a RAC system for our program, which was 100% dependant on the limitations of helicopter bombing, we were excited to push the button on our new units and mitigate avalanche risk in any kind of weather and at any time of day.
We quickly realize the operational risk band (ORB) is indeed dynamic. Typically, we would ride the curve upwards as the risk trended higher, until we reached a point near the top when numerous natural avalanches would begin to affect the highway and it would be closed. We would continue forecasting until daylight, before flying to do avalanche control. In other words, we applied explosives (heli-bombed) well after the risk peaked, on the downward side of the curve of our ORB.
We quickly figured out the efficient use of any RAC is to flatten the curve* well before reaching the top of the ORB. Firing of a RAC is very much a forecasting tool, but it also creates a bias that you have full control of at that moment. We recall telling our managers that preventative closures would now be unlikely at 35 Mile with 24/7 avalanche control capability.
What we didn’t realize is there are other factors at play that restrict the ability to actually fire the O’Bellx units when you want to. Our Northwest Avalanche Program has site-specific safety measures we put into action that increase safety to highway users while maintaining an open highway.
These measures will remain in our toolbox, allowing us additional time to forecast to specific conditions when firing is delayed.
OVERALL IMPRESSION
The O’Bellx is very well suited to this site. Mobilisation and demobilisation has been accomplished in a few hours, which included transport back to Terrace, and is the clear win. As the units function on gas, there are no explosive charges to prime and load. No special licensing is required and there are no explosive misfires to deal with. Finally, avalanche control from the safety and comfort of a warm dry truck can not be overstated.
*“Flatten the curve”: We had no idea just how powerful the term would be in the months to come.
