Blasting Information on Ajax Mine

Posted by Stop Ajax Mine on August 5th, 2013 12:55am

Due to all the talk and discussion of blasting around the mine, the following was created as a primer for more information for those who are looking to get more informed about the mine and the impact of blasting on the Ajax proposal.

If you are going to do more stories about Ajax blasting concerns in the future, you should review the attached documents. 

The first one is the Orica test blast report, which was done for KGHM Ajax.

The second document is the review of this report by Dr. Katsabanis. 

The Katsabanis review concluded that the model Ajax proposed to use to estimate ground vibrations is capable of predicting blast vibrations.  However, there are two impacts from blasting: ground vibrations and air blasts (or shock waves).  Dr. Katsabanis did not review the Orica report for air blast modeling, as you will find out if you read the report.

Even though Dr. Katsabanis accepted the model Ajax is using for predicting ground vibrations, he was critical of the Orica report for not providing sufficient data for the test blasts.  As Dr. Katsabanis states:

The report provides scant information on the experimental procedures that were followed. The characteristics of the signature holes would be of interest to the reader. Such information is at minimum the diameter, burden, loading, priming and location.

If you read the Orica report, you will find, as Dr. Katsabanis concluded, no information on "loading".  This I take to mean the "powder factor" or the "blast ratio".  This is the amount of explosive material used to displace the rock, often expressed in the tonnage of rock per kilogram of explosive used.  In other words, we really don't know how big the February 2011 test blasts were.

Without the data Dr. Katsabanis describes as scant, I can't see how one can extrapolate the effects of a full size production blast based on smaller blasts of unknown size.  If Ajax has VERIFIABLE information on the size of the 2011 test blasts, this data should be released. 

A third document of interest is a report from the University of Leeds: Full Scale Investigation into the Origins and Prediction of Air Overpressure from Quarry Blasting.  I will send this report separately because of its length.  Although this report is concerned with smaller-scale rock quarry blasts, as opposed to large-scale open pit mine blasts, the issues examined in the report apply to Ajax.

Of particular interest are the sections on meteorological conditions (pages 41 and 46).  These sections suggest that air overpressure could be "reinforced" as much as 4-5 km from the blast zone (page 41) and that blasting should be avoided during such conditions as: temperature inversions; moderate to strong winds towards sensitive areas; foggy, hazy or smoky conditions with little or no wind; and still, cloudy days with a low cloud ceiling (page 47).  These conditions describe the often stagnant winter inversions Kamloops experiences from October to March.

A fourth report of interest is a Draft Blast Management Plan prepared by BHP Billiton, the world's largest mining company, revenue wise, for a coal mine in Australia.  Of particular interest is the right of property owners to have a structural inspection done before any blasting occurs within 3 km of the blasting zone for this mine, as stated in Section 3.3:

Residents within 3km of blasting have been sent letters to inform them that they are entitled to request structural inspections on their property.

I believe a similar zone needs to be established for the Ajax mine before any blasting occurs, including test blasts. Whether 3 km is adequate for Ajax needs to be addressed.  Geological conditions in the Aberdeen area may warrant a larger zone, given unstable slopes in this area.  The Plura Hills United Church and Aberdeen Elementary School are approximately 3 km. from the Ajax pit.

Related Links:

Orica Test Blast Report

Orica Katsabanis Review

BHP Billiton Draft Blast Management Plan


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