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Dissolved Metals <br />Historic Averages <br />Q4 2011 <br />Q1 2012 <br />Q2 2012 <br />Q3 2012 <br />Lead <br />0.008 <br />0.0003 <br />0.0001 <br />0.0008 <br />0.00111 mg/L <br />0.29 mg /L <br />Zinc <br />0.302 <br />0.37 <br />0.41 <br />0.31 <br />The Yellow Rose Drift also contributed approximately 10 gallons per minute to the flow, and as is <br />seen from the results in Tables G -2 and G -3, this water is of excellent quality. Table G -5 calculates <br />the mass balance of zinc as it moves through the mine and also in the surface water system <br />(discussed in the next section). It is calculated in grams per hour. The results show that the amount <br />of zinc drops dramatically from the Atlas drift to the mine exit. For example, the Q1 2012 results <br />show that the Atlas drift contributes 42.7 grams per hour of zinc, and the Revenue Tunnel water <br />upstream of Atlas only has 0.45 grams per hour, yet the water measured in the Revenue Tunnel just <br />prior to the connection with the Yellow Rose Drift (UG -2), shows only 6.98 grams per hour. <br />Therefore, the majority of the zinc is being removed from the system in the Revenue Tunnel. <br />Research has shown that a large amount of zinc in a neutral pH water does tend to drop out over <br />time. Also, organics can precipitate out zinc if present. There were at least 10 minor blockages of <br />the Revenue Ditch (in the Tunnel) underground between the Atlas Drift and the Yellow Rose Drift <br />at the time of the Q1 2012 sampling. These blockages contain old timber with some likely fungus <br />and bacteria which may be removing some zinc. Also, magnesium minerals are known to replace <br />zinc in the water, and these are also present in the andesite rocks which make up the base of the <br />mine water ditch. Zinc is also known to precipitate out as zinc hydroxide by a variety of chemical <br />and physical means. It is believed that a combination of these items is occurring to reduce the zinc <br />levels These possibilities may provide some benefits to mitigation of zinc in the discharge once <br />CDPHE establishes the actual permit standards. <br />It is important to point out that the flows in the mine can vary significantly with the seasons and <br />with particular years, so additional data from other quarters will be evaluated as they are sampled. <br />Table G -4 shows the historic averages for these dissolved metals, compared to recent sampling. The <br />recent sampling shows slightly higher zinc levels than the historical average, but are close. The lead <br />levels are slightly lower, but also still close to the averages. <br />Table G -4 - Mine Discharge Water Quality Comparison <br />Revenue Mine August 2012 <br />G -9 <br />