SAN GREGORIO OPERATION

Overview

OMI's San Gregorio gold mining and processing operations are located approximately 450 kilometers north of Montevideo. The principal towns in the region are Minas de Corrales, Tacuarembó and Rivera. Sealed roads link the towns and mine to Montevideo.

This region is generally flat-lying with undulating hills; vegetation is restricted to river courses. The climate is temperate with consistent rainfall throughout the year. The land surrounding the mine is predominantly used for agriculture.

Mining is by conventional drill and blast, load and haul open pit methods using 6m benches excavated in two 3-meter flitches. The company owned mining equipment currently includes;

PC1250 6.7m3 capacity excavator (2)
50t payload dump trucks (8)
50,000L water dump truck (1)
4.7 m3 capacity front end loader (1)
35 t wheel dozer (1)
70 t bull dozer (1)
Graders (2)
6 x 6 Oshkosh service fuel truck (1)
Pantera 1500 drill rigs (3)

Mining of satellite pits and pre-strip is performed using contractors with smaller equipment. Ore from satellite pits is trucked to the process plant using road trucks

The ore treatment plant is a conventional carbon in leach (CIL) plant built by Minproc in 1996 and commissioned in January 1997. The plant, with a nominal throughput of 1.1Mtpa, comprises a single stage primary crushing circuit using a 500mm aperture grizzly and a jaw crusher fed using a Front End Loader (FEL). The nominal crushed ore size is 100% passing 150mm. The crushed ore is conveyed to a surge stockpile with a nominal live capacity of 1,200t. Up to 2,000t of crushed ore are maintained on an adjacent stockpile to cater for extended primary crusher stoppage. The crushed ore is reclaimed from the main stockpile using ore feeders and fed into a SAG/ball mill circuit using a conveyor. SAG mill scats are crushed in a 2-stage secondary crushing circuit using cone crushers, to prevent build-up of critical size material in the SAG mill. The ball mill runs in closed circuit, utilizing cyclones for product size control. The grinding circuit nominal product size is 80% passing 150μm.

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Power for the site is supplied from the national grid, and some 3,400,000kW/hr of power are purchased from the grid each month to supply overall power to the project of 4,800kW per operating hour. A backup power plant sufficient to run the leach plant is available.

Water is supplied from a raw water dam upstream from the tailings store facility. The dam captures the local catchments and has provided sufficient capacity to date. A causeway has been constructed across the Arroyo Corrales to haul ore directly to the ore treatment plant at San Gregorio. At times flooding will prevent the causeway from being used, however flood durations are low, and not expected to be a significant issue.

Gold, silver and base metal samples for exploration, mine and the process plant are analyzed at the Company's onsite Laboratory. The laboratory processes around 12,000 samples per month which translates to approximately 21,000 analyses. Of the total 31% are for the plant, 27 % for exploration and 42% for the mine.