Since 1986, Coeur has mined at Rochester by conventional open pit, drill and blast, truck, and loader methods.
Operations at Rochester consist of mining from in situ and stockpiled open pit sources that is fed directly into the primary crusher dump pocket and crushed product is placed directly onto a heap leach pad for processing.
Blasting services are contracted at the Rochester Mine. The contractor is responsible for obtaining, securing explosive agents, loading blast holes, and initiating the blasts.
Blast patterns and locations are laid out by Coeur Rochester engineers and surveyors. Three blast hole drills are used to drill the typical square blast pattern of 15 × 15 ft. on a 30 ft.-high bench, with 3 ft. of sub drill. Shots typically consist of 350 to 450 holes. Three row trim shots are used near highwalls to protect the highwall from blast damage. Trim shots are laid out on a 15 × 15 ft. pattern.
Current blasting practices at Rochester employ the use of Ammonium Nitrate and Fuel Oil (ANFO). Emulsion blends are used where necessary. Non-electric detonators are used for initiating and timing the blast. Stemming depth with crushed rock varies but is typically 11 ft. deep
All waste rock is placed either inside the pit perimeter as backfill, or outside the pit in the approved RDSs. Waste rock is defined as material below cut-off; however, it could still contain some mineralization. It is then further evaluated to deter ........
