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irrelevant. This is supported by the fact that before mining the Cripple Creek diatreme <br />• was naturally drained to an elevation of 9,600 ft, up to 1,000 feet below the ground <br />surface of the diatremal area. Additional drainage by underground workings and/or <br />tunnels will not change the infiltration rate at the surface under these conditions. <br />• The elevation of the Nevada mountain basins is in general similar to the Cripple Creek <br />diatreme, particularly the higher elevations where the precipitation is also higher. <br />• The precipitation rate is a variable in the evaluation, so this can be made comparable <br />in both cases. Seasonal precipitation patterns are also similar. <br />DRMS proposes to require CC&V to utilize the higher infiltration rate (6.99 inches per year). <br />The use of this infiltration rate would reduce to zero the amount of infiltration water captured <br />by the diatreme from the surrounding granitic materials. While the contribution from this <br />source is expected to be smaller than direct infiltration to the diatreme, due to the lower <br />hydraulic conductivity of the Precambrian materials, it is not expected or observed to be zero. <br />Accordingly the DRMS requirement would appear to be unreasonable. Other than this effect, <br />the change to the higher infiltration will have no impact on the analysis results: the water <br />balance analysis in the diatreme is calibrated against the measured flow at the Carlton Tunnel <br />of the intercepted regional ground water, and is not dependent on, or sensitive to, the area <br />from which the infiltration is collected, or the rate of that infiltration. <br />d) The operator states, "The Carlton Tunnel today captures essentially all the ground <br />• water in the district. The flow from the Carlton Tunnel represents the collection of <br />ground water infiltration to the diatremal materials as described". Under the <br />infiltration section, the operator states, "Evaluation of the data indicates that the <br />infiltration rate is not in fact representative of the ground water system in the <br />district. On an annual basis the infiltration rate has been computed in the same <br />way and the results are presented in Figure 5. This figure shows that the ground <br />water yield decreases with precipitation, indicating that some process other than <br />precipitation and infiltration is influencing the flow rates at the Carlton Tunnel." <br />Under "Impacts of Mining", the operator states, "The infiltration to the regional <br />groundwater system is driven by precipitation". The Division is a bit confused by <br />the conflicting statement. Is CC&V saying the discharge from the Carlton Tunnel <br />could be impacted by other unknown contributors, other than the rate of <br />infiltration from the mining district expressing itself as ground water flow at the <br />tunnel? Please explain. <br />Response. <br />The statement in the report is that "Evaluation of the data indicates that this infiltration rate <br />is not in fact representative of the groundwater system in the District" to show difference <br />with the DBMS quote). "This" refers to the normal way to compute infiltration rate, by <br />dividing the observed ground water infiltration flow by the observed precipitation incident on <br />the catchment for each year. It is an observation that this relationship doesn't work in the case <br />of the Cripple Creek diatreme. <br />• The evaluation of the hydrology of the diatreme that is presented in the report was developed <br />to explain the observed facts. Those include the fact that the percentage of the precipitation <br />incident on the diatremal surface that flows out of the Carlton Tunnel is highest when the <br />27