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February 4, 2009 <br />Pg. 5 <br />• Table A-7: There are large discrepancies between the data reported for 2007 and 2008 for <br />antimony, cobalt, copper, iron, manganese, nickel, zinc, sulfate, and others. Can these be <br />explained? <br />• Piper Diagrams: The toe seep is shown to have a relative proportion of carbonate + <br />bicarbonate equal to approximately 20%. However, Table A-3 shows the pH of the seep as <br />below 4.0, which means the activity of carbonate + bicarbonate should be below 105, <br />equivalent to a combined concentration of less than 1 mg/L. Please explain. <br />• Pg. 19 states that pH levels in the underground sump differ significantly from the waste rock toe <br />seep, yet Table A-3 shows the UG sump pH = 3.7 and the toe seep = 3.87. Please explain. <br />• Pg. 20: Dilution is offered as an explanation for the `loss' of Al, Cd, Mn, and Zn along flow <br />pathways #1 and #2, yet As, Cu, Pb, and Se increase along these pathways. Would not <br />dilution cause a `loss' of these elements as well? Would Eh-pH dependency of As, Cu, Mn, and <br />Se be a more plausible explanation for the observed concentration variations? <br />• Pg. 23: Please explain how "physical disturbance/ environmental stabilization" causes reduced <br />mineral solubility. <br />• Pg. 23: Please explain how the handling of the waste rock, and what types of handling, lends to <br />oxidation and loss of sulfur. <br />• Pg. 23: In reference to the statement "...the chemical signature of the waste rock indicates the <br />metals have not been leached, and that there has been minimal water contact and transport <br />over time", please provide the geochemical or hydrologic lines of evidence for these <br />conclusions. <br />• Pg. 24: Please describe how the sampling effort created dilution in Well C. <br />• Pg. 24: Please explain the statement "recharge occurred as a result of forced water flow through <br />the un-washed alluvium formation." Is this referring to a different process than advection- <br />dispersion? <br />• Pg. 26: Please elaborate on the studies that indicate that water within Deadman Gulch is not <br />reaching residential well water systems. <br />• Pg. 26: Please elaborate on the mixing-zone studies in the Lake Fork that indicated "no <br />material impact" from Deadman Gulch.