As part of the Mt. Currie Safety Risk Assessment, licensed blasters will be conducting Seismic Refraction Surveys commencing on July 26th. The work is expected to continue for a maximum of a week.
These surveys are conducted by laying a survey line and cable, then a corresponding line of small holes are hand dug with small explosive charges laid in each hole. When these are detonated, it creates seismic energy that is then measured by the sensors. The process is repeated across the prescribed survey area, building up detailed information that is used to calculate the density of earth and bedrock.
These charges are small and set away from where rock falls on Mt. Currie have originated. All work will be conducted in compliance with the BC Wildfire Act and corresponding Wildfire Regulation, which regulates high risk activities including the use of spark-producing tools and the preparation or use of explosives. The fire danger rating for the Pemberton Area is currently Level 4 and the survey team is liaising with the Pemberton Fire Service to ensure all precautions are taken. Should the fire danger rating increase to Level 5 and remain there for three days, all work must cease until the fire danger rating has been downgraded.
FAQ re Seismic Refraction Surveys
One aspect of the Mt Currie Landslide Hazard Assessment and Risk Analysis study that is underway is studying the density and volume of previous landslides from Mt Currie as part of assessing the potential for future landslides of a similar or greater volume. Seismic Refraction Surveys are the method used to gather this data.
Q: What is the process for Seismic Refraction Surveys?
A: A survey line of cable and sensors is laid, then a corresponding line of small holes are hand dug with small explosive charges laid in each hole. When these are detonated, it creates seismic energy that is then measured by the sensors. The process is repeated across the prescribed survey area, building up detailed information that is used to calculate the density of earth and bedrock.
Q: Are these people qualified to be handling explosives?
A: A licensed holder of a WCB Blasters certificate will supervise the handling and detonation of the explosives.
Q: What is this doing to the environment?
A: The smallest feasible charge size is used to record the required information, and there is strict observance of setback distances from waterways, as laid out in the Guidelines for the Use of Explosives in or Near Canadian Fisheries Waters.
Q: So, rockfall from Mt Currie may be increasing, and you are proposing to set off explosives near the base of it. Won’t that potentially make the problem worse!?
A: The short answer is that the charges are small and set well away from where the rockfalls have originated. The longer answer: the smallest feasible charge size is used to record the required information, and the seismic energy created by each set of charges is equivalent to an excavator working on a construction site. The survey area is where historical landslides have settled, not on the mountain itself and not anywhere near where rockfalls are originating.
Q: How long will the work continue?
A: It is anticipated that the process would take a maximum of one week.
Q: What company will be carrying out the work?
A: Frontier Geosciences. To learn more: https://lilwat.ca/wp-content/uploads/2017/07/Seismic_Refraction_Surveys_using_explosives.pdf
Background
Observed rock fall from Mt Currie has increased in the past few years, and was confirmed by an initial Information Note, “2016 Mount Currie Rock Fall and Local Instabilities,” from the Ministry of Forests, Lands and Natural Resource Operations (MFLNRO) in October 2016. MFLNRO also recommended that a detailed assessment be completed to fully understand the risks posed by this increased movement and the potential for future landslides.
This assessment work is now underway, thanks to a funding commitment from Emergency Management BC (EMBC).
A review of existing data on Mt Currie has been conducted, and field survey work (which can only be conducted in the summer) will begin on July 26, 2017 and is expected to take no more than one week. The work will include aerial, ground and seismic surveys.
One aspect of this work is studying the density and volume of previous landslides from Mt Currie as part of assessing the potential for future landslides of a similar or greater volume. Seismic Refraction Surveys are the method used to gather this data.
A survey line of cable and sensors will be laid, and then a corresponding line of small holes will be hand dug and small explosive charges will be laid in each hole. When the charges are detonated, a seismic energy will be created that will then be measured by the sensors. The process will be repeated across the prescribed survey area, building up detailed information that will then be used to calculate the density of earth and bedrock.
Please be aware that the sound of these subterreanean explosions may be audible over the next week – particularly near the golf course.
More information about this project, including the planned field work, is available on the Mt Currie Landslide Hazard Assessment and Risk Analysis project page.
Photo courtesy Arriya Kuiper from her instagram.com/thewellnessalmanac takeover.
The Wellness Almanac 
WOW Lisa I just have to take you on that geology walk soon because it is so currently topical.
I’m away next week but after that ……hu
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