This blasting hazard alert pertains to Orica Unitronic 500electronic detonators date coded before Nov. 15, 2009.

Orica has issued a recall of these detonators. The Orica recall notice is included as part of this blasting alert.

Since 2006, there have been six unplanned detonations involving the use of the Orica Uni tronic electronic detonator blasting system. Four of the unplanneddetonations occurred at surface mines in the United States and two occurred at surface mines in Australia. Four of the unplanned detonations occurred upon the act of aborting the programming sequence and two occurred during programming of the detonators.

The last unplanned detonation was in December 2009 at a surface coal mine in Alabama. The mines were using the Orica Uni tronic™ blasting system to set-up the blasts, check the circuitry, program and arm the electronic detonators for blasting, and to detonate the round.

In each instance, once all personnel were off the blast area and at a point of safety (blast area secured), the blaster connected the circuit to the Orica Blast Box and then began the detection and programming process. While the detonators were being programmed or if an abort command was issued, one of the blast holes unexpectedly detonated.

No injuries or property damage were reported.

The investigations of these incidents have determined the unplanned detonations occurred most likely because of faulty or damaged electronic devices on the electronic detonator boards used as an internal component of the Uni tronic 500 electronic detonator. Orica upgraded all Blast Boxes with a controlled abort procedure in July 2008 and with more than five million electronic detonators sold since then, there has not been an unplanned detonation during an abort.

To address the unplanned detonations during programming, Orica implemented an enhanced test protocol in August 2009to detect circuit boards in its manufacturing process that may have a faulty or damaged electronic device. Since implementing this new testing protocol, there has not been an unplanned detonation during the programming sequence using the tested electronic detonators in more than 1 million that were sold.

Means of identification to determine Uni tronic 500 electronic detonators date coded before Nov. 15, 2009.