On August 5, 2020 we conducted a scheduled blast inside the South East Ridgeline of the quarry. The blast was scheduled for 2:30 p.m., however, the blast was slightly delayed. The blast siren was activated at approximately 2:50 p.m. and the blast was fired at 2:51 p.m. All holes fired as expected and the resulting vibrations were felt in the Exshaw community.

The location of today’s blast was in a corner of the Quarry that has not been mined for many years. As shared in a previous community session, we have come to a point in the development of the quarry that this material needs to be removed. We have taken close consideration to the proximity of the community and have designed the blasting to mitigate as much of the risk as possible.

All blasts that are conducted at the quarry have vibration (mm/s) and airblast (dB) recorded on the monitor located at the Exshaw Water Treatment Plant. We have blasted the adjacent shots on this level previously this year on the July 23, July 3, and June 10. All had very low readings that were not felt widely in the plant or community. The vibrations from today’s blast were predicted to be in line with these. What we experienced was higher than predicted.

When planning a blast, we plan for our blasting vibration to be 10 times lower than our threshold values. We target this outcome so that if we do get an unexpected result, we are still well within safe limits. Please be rest assured that despite having felt the blast more strongly than usual, we were still well within safe limits for structural and personal safety.

For a recent update, click here.

Any further questions can be directed to me via Janet Brygger at: janet.brygger@lafargeholcim.com

Kind regards,
Dylan Treadwell
Quarry Manager