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1292). In excess of one billion tons of pyrite are estimated to exist in rocks in the vicinity of <br /> the Sunnyside Mine (assuming 5 cubic miles of propylitzed rocks with 1.0% pyrite). The <br /> weathering of this dispersed pyrite as well as other mineralization has resulted in the pervasive <br /> staining which is common in rocks throughout the area (e.g. Red Mountains 1, 2, and 3). <br /> 3.1.2 Bedrock Permeability <br /> Permeability is the measure of the ability of a rock or soil to transmit a fluid (usually water) <br /> under a hydraulic gradient (Lohman, 1979). Much can be inferred about the permeability in the <br /> vicinity of the Sunnyside Mine based on site geology and hydrogeologic observations. <br /> The intergranular permeability of pyroclastic sediments is typically very low and the <br /> intergranular permeability of volcanic flows and tuffs is insignificant. Freeze and Cherry (1979, <br /> p. 29) estimate the range of intergranular permeability of igneous rocks as varying from <br /> approximately 10-R cm/sec to less than 10" cm/sec. In such rocks the vast majority of water <br /> is transmitted via secondary fracture permeability. The permeability of fractured igneous rocks <br /> ranges from 10-6 cm/sec to greater than 10-Z cm/sec. The location, extent, openness, and <br /> orientation of fracturing controls the hydraulics of the bedrock flow system. <br /> Fracture permeability in the vicinity of the Sunnyside Mine is anisotropic. Permeability is <br /> greater in a northeast/southwest direction due to the dominant fracture orientation within the <br /> Eureka graben (see section 3.1. 1). In addition, fracture permeability is greater in the welded <br /> tuffs and flows than in the unwelded units. The southwest dip in the vicinity of the mine results <br /> sanjuan\sunny\110361\oct91.Rpt 12 <br /> a simon [H,\UPnu=nnmun <br />