2008-08-25_REVISION - M1980244 (3)

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J. Given the lack of adequate ground water monitoring well data in Poverty Gulch (North Cresson Mine), with the exception of PGMW-2 which has been dry since construction in 2001, the Division requests at least two more additional wells be drilled and completed prior to initiating impacts in the area. The Division allowed the current monitoring with limited data to be in place, since the plugging of the two monitoring wells (PGMW-1A &1B), because there are no current active Cresson Project disturbances in the area and none were proposed under AM-08. The current mining plan proposes to disturb a considerable amount of acres as part of the mine life extension. Even though there is a lack of measurable drainage, except in association with a heavy precipitation event, and a few wet areas down gradient, which may or may not get shallow ground water flow from upgardient areas, there is still the potential for some adverse effect to the overall hydrologic balance. That is why the Division recommended to CC&V, in the reclamation and mining portions to completely backfill the mine pits in the area to original contour, instead of the current partial backfill proposal. Please provide a location for the additional ground water monitoring wells for these areas as part of your response to the adequacy. The DRMS would like CC&V to collect as much quarterly data as possible prior to affecting acres in the area. K. The Grassy Valley water balance modeling utilized the Gold Sim (version 9.60), the same program used to model the water balance for the valley leach facility. This is a graphical program that is supposed to determine the dynamic deterministic or stochastic simulations. The Division is not even certain this modeling program can accurately predict when a solution placed in a portions of a lined pad will report to the pregnant solution let alone predict long term water balance for an open natural system with changing mining and backfilling activities. What the Division would like to see are the modules for the program so we can understand the inputs used to get the water balance and if it indeed mimics site specific conditions. L. The long term characterization of the water quality devotes great detail to the impact of sulfide oxidation. What about sulfate salts that may exist on surfaces of already oxidized material and are more readily flushed and mobilized than are the products of more refectory sulfides that are present in the un-oxidized material? Please comment on this in terms of how much of this material might be present and what effect it might have on water quality? M. Vol. II PG. 15 states that sulfate and zinc releases will not result in loading increases as calculated, because of factors such as the slow transport of the constituents and water sequestration. This reasoning is not entirely clear and requires further explanation. Additionally, this analysis begs the question that after the plug of newly released sulfate and zinc have been migrating downward for some years, is it reasonable to assume that the condition of chemical steady state can be attained through the vertical section of the diaterem in which those calculated concentrations (22,000 mg/1 for sulfate, and 159 mg/1 for zinc) may actually be sustained? N. A statement is made that the alkalinity has leveled off in the Carlton Tunnel Discharge. In fact, the three highest alkalinity values ever measured have been collected in the past 5 sampling events shown on Figure 18, suggesting the alkalinity values are on the rise again. It may be beneficial from a modeling standpoint to quantify why alkalinity has been increasing in recent years. If future overburden leachate turns out not to be as predicted, 11