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<br /> <br />3. Determine the means by which Zn and other metals are removed from the <br />groundwater as they exit the Carlton tunnel. Verify whether Zn is adsorbed by Ferrihydrite. <br />The precipitation of calcite in the stream outside the Carlton tunnel can be explained <br />as follows. Ca-HCO, groundwater, which occurs in the diatreme, is supersaturated <br />with COZ. Upon exposure to the atmosphere, COi volatalizes, and calcite precipitates <br />at the mouth of the adit. (There may be other means of precipitation as well; in fact, <br />we have no documented evidence that the white precipitate outside the tunnel is <br />indeed calcite.) This precipitation phenomenon occurs rapidly enough to either adsorb <br />or otherwise incorporate stray ions such as Zn. If Zn is removed by this method, and <br />this is the only method for Zn removal, then the quality of the discharge water will be <br />sensitive to changes in all the parameters that lead to the production of the calcite. <br />Slight changes in pH, a loss of COZ within the diatreme, or an excess loss of calcite <br />from the diatreme rocks, all could affect the saturation state of calcite in the <br />groundwater and thereby its ability to precipitate outside ground and adsorb Zn. <br />4. Quantify the water quality that will result as rain/snowmelt water flows through <br />waste rock in pits and piles. Are previous tests, which were based on humidity cell data, <br />appropriate to determine the water quality or should it be assessed from sequential batch tests? <br />5. Adjust the hydrologic and hydrochemical model to account for the abundance of waste <br />rock on the surface, and the excess surface area generated from the crushed rock. <br />Previous models accounted only for acid generation in the footprint of the Cresson pit <br />area. However, acid will be generated not only in the upper surface of the waste but <br />all through the waste. Also, the Iron Clad pit, Globe Hill pit, Arequa Gulch waste <br />rock, Squaw Gulch waste rock, and the unreclaimed waste rock piles elsewhere in the <br />area all will contribute to acid in the pit. <br />6. Adjust the hydrologic and hydrochemical models to account for the abundance of acid <br />neutralizing water in the ground. <br />Previous modeling treats the acid neutralizing source as an effectively infinite reservoir. <br />However, assuming the mechanism by which neutralizing water is generated is as it <br />was modeled by HCI, the acid neutralizing water reservoir would be depleted in part <br />because acid would form in waste rock areas that previously were occupied either by <br />nothing or by pyrite free rock. <br />Adjust the models to account for the smaller size of the diatreme with depth. <br />Previous models assumed that the diatreme outcrop area was continuous to depth, and <br />