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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 -4 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 large <br />amounts over distance and time. Also, organics can precipitate out zinc if present. There are at least <br />10 minor blockages of the Revenue Ditch (in the Tunnel) underground between the Atlas Drift and <br />the Yellow Rose Drift. These blockages contain old timber with some likely fungus and bacteria <br />which may be removing some zinc. Also, magnesium minerals are known to replace zinc in the <br />water, and these are also present in the andesite rocks which make up the base of the Ditch. Zinc is <br />also known to precipitate out as zinc hydroxide by a variety of chemical and physical means. It is <br />believed that a combination of these items is occurring to reduce the zinc levels These possibilities <br />may provide some benefits to mitigation of zinc in the discharge once CDPHE establishes the <br />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. <br />While the values from recent sampling are higher than the historical averages for zinc, the recent <br />samples are from low -flow times of the year. Q2 2012 and Q3 2012 data is expected to show lower <br />concentration since the spring and summer flows are typically much higher than the fall and winter <br />flows. <br />Revenue Mine August 2012 G -9 <br />