2012-02-28_REVISION - M1980244 (77)

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i paSmiurH 1 of the gold bearing ore to the bubble surfaces. The flotation feed conditioning tank feeds the rougher flotation cells via a flotation feed box. Five rougher flotation cells (approximately 13,000 gallons each) in series will receive flotation feed from the flotation feed box. The gold bearing ore that is floated (flotation concentrate) from the rougher flotation circuit will flow to the Regrind Cyclone Feed Sump. The flotation processed ore will exit the last flotation cell to the Flotation Processed Ore Sump. 2.4. Regrind Circuit Design Summary Squaw Gulch High Grade Mill Facilities 1/24/2012 Page 3 of 6 The flotation concentrate is further reduced in size to approximately 25 microns in diameter in the Regrind Circuit to allow more gold liberation in the Leach Circuit. The flotation concentrate from the regrind cyclone feed sump is pumped to the Regrind Cyclones. The concentrate will be classified by the cyclone into fine and coarse materials like the Primary Cyclone Cluster operation in the comminution circuit. The underflow (coarse particles) of the regrind cyclones will flow by gravity to the Regrind Mill Feed Pump Box. From the Regrind Mill Feed Pump Box, the underflow will be introduced into the Regrind Mill. The Regrind Mill will further reduce the flotation concentrate particle size to approximately 25 microns. From the Regrind Mill, the fine slurry transfers to the Regrind Discharge Sump. The overflow (fine particles) from the Regrind Cyclones will by -pass the Regrind Mill and will gravity flow to the Regrind Discharge Sump. The fine concentrate slurry in the Regrind Discharge Sump is pumped to the Concentrate Thickener. The thickener allows the particles in the slurry to settle and allows clear water to be captured and re -used in the High Grade Mill facilities. This decreases the amount of fresh water needed to operate the mill, which is anticipated at a rate of 290 gpm. The clear water from the thickener is pumped to the Neutral pH Process Water Tank. The de- watered concentrate from the thickener is pumped to the pH Adjustment Tank in the Leach Circuit. 2.5. Leach Circuit The Leach Circuit dissolves the gold in the fine concentrate slurry from the Regrind Circuit by the addition of a lime (transferred from a single 50 ton lime silo) and cyanide solution (transferred from two 25,000 gallon storage silos). Leach reagents in the form of lime slurry and cyanide solution will be added to the gold concentrate leach feed in the pH adjustment tank. The overflow from the Carbon -In -Pulp (CIP) processed ore thickener, containing recycled cyanide and loaded carbon screen underflow will also flow into the pH Adjustment Tank to reduce the slurry density to approximately 40% solids