2008-09-17_REVISION - M1980244 (28)

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precipitation is lowest, and lowest when the precipitation is highest. This apparent paradox • has to be the result of some process other than the normal infiltration process, where the well- accepted observation is that the higher the rainfall, the higher the percentage of that precipitation that infiltrates and appears as regional ground water flow as intercepted by the Carlton Tunnel (see for example the Maxey and Eakin results). The reason for the paradoxical infiltration rate is that the large water storage in the diatreme dominates and greatly attenuates the flow variation of the regional ground water table from the Carlton Tunnel. In dry years, the diatreme gradually drains to the regional ground water table, maintaining the flow rate in the Carlton Tunnel at a level that is considerably higher than would be observed under steady-state conditions at that low precipitation rate. Thus, when the flow of the regional ground water from the Tunnel is divided by the total incident precipitation for that low precipitation year, a high apparent infiltration is computed. Conversely, in wet years the storage in the diatreme is partially refilled, and the flow of the regional ground water from the Carlton Tunnel is less than it would occur under steady state conditions at that high precipitation rate. When the wet year flow of the regional ground water from the Tunnel is divided by the higher precipitation, a low apparent infiltration is computed. This process is indeed driven by infiltration as stated in the report, and this statement is not in conflict with the observations about the process by which this infiltration reports as flow of the regional ground water at the Carlton Tunnel. However, the infiltration rate cannot be reliably considered on an annual basis, because the storage of the system attenuates the flow so • much between input (infiltration) and output (flow at the Carlton Tunnel portal). The model that has been developed for the hydrologic system in the diatreme includes the very significant storage effect, and calibrates quite closely with the observed flow for the period 1993 to the present. CC&V is not making any claim that other unknown contributors are impacting flow of the regional ground water at the Carlton Tunnel. There is no evidence that this is the case. However, it does appear that the Cripple Creek diatreme acts as a powerful drain, and collects ground water from a small distance (but significant area) beyond the physical boundaries of the diatreme and of the mining district. E. CC&V'S consultants stated, "during development of the proposed MLE, project activities, the net effect of the WHEX portion of the East Cresson Mine and the ECOSA is expected to reduce flows to Grassy Creek. The current average annual flow rate is about 40 gpm. Modeling results, including sensitivity analyses, suggests that during development the average annual flow rate at GV-03 may range from 25 to 31inches. Please provide a detailed flow rate measuring plan for Grassy Creek and piezometer water level measuring plan for the riparian areas for approval by the DRMS. Is the shallow alluvium aquifer that currently feeds the wetlands in these areas disconnected from the bed rock aquifer? Has CC&V conducted a well draw down pump test, to show these two aquifers are not connected? What about existing fracture zones in the bed rock, what impact will additional mining have on the transmissivity of water from the alluvial aquifer to the bed rock aquifer? With • out well draw down pumping tests to show the disconnection of the alluvial aquifer from the deep bed rock aquifer, how can CC&V assure the Division that the wetlands will not be permanently affected when mining extends beyond the elevation of the alluvial aquifer? CC&V's hydrologic consultants recommended that the operator supplement additional 29