The San Dimas mine includes five main underground gold and silver mining areas: West Block (San Antonio mine), Sinaloa Graben Block (Graben Block), Central Block, Tayoltita Block, and the Arana Hanging-wall Block (Santa Rita mine). In 2020, 68% of ROM production came from the Central Block, 29% from the Sinaloa Graben and 3% from the Tayoltita Block and other areas.
Access to the mining areas is achieved by adits and internal ramps. The Central Block and Sinaloa Graben rely solely on truck haulage, whereas Tayoltita ROM material is transported to the surface stockpile via rail. Main accesses are typically driven at 5 m wide by 5 m high, with accesses to the stopes at 3 m wide by 3 m high. Typical rail haulageway dimensions are 3.5 m wide by 3.5 m high.
Internal ramps connect stopes from both the hanging wall and foot wall, and often, when two or more veins are in close proximity, single ramps can provide access to multiple veins.
The predominant mining methods at the San Dimas mine are mechanized cut-and-fill and longhole mining. Longhole mining was introduced in 2012 and is becoming increasingly important.
Cut-and-fill mining is carried out using jumbo or jackleg drills and load-haul-dump (LHD) machines. Minimum mining widths of 2.5 m and 0.8 m for jumbo and jackleg mining, respectively, may be attainable. Waste rock is used as fill material and provides both wall support and a working base from which to take subsequent cuts afte ........
