Laserfiche WebLink
<br />watersheds other than those draining the Cripple Creek Mining District. (You also probably <br />know that water has always been scarce in the area.) <br />The ground water that CC&V is monitoring, at most, contributes a small fraction to the <br />downgradient waters where it is thoroughly mixed so as to be indistinguishable from other <br />waters. In most likely fact, the water draining from the Carlton Tunnel is representative of a <br />good part of the ground water from the District, but even it is affected by deeper sources. <br />As one result, a meaningful use classification is essentially impossible to assign to ground water, <br />if for no other reason than because there is little agreement on exactly what existing and <br />reasonably-potential future uses are, and no way to clearly extrapolate from current uses because <br />there are no current uses. <br />Quite likely, the most appropriate approach in this site-specific case is to employ the "practice <br />based permit conditions" authorized by the Mined Land Reclamation Board's Regulations <br />(§3.1.7). CC&V employs numerous practice-based controls to protect ground water. These <br />include the design and construction of the Valley Leach Facility itself, management of <br />overburden, monitoring of the underdrain system, monitoring of the Leak Detection System, <br />monitoring of the Low Volume Solution Collection System, monitoring of surface water, <br />monitoring of ground water, and reclamation. <br />Threshold criteria might be established to enable CC&V to pay particular attention to substantive <br />rises in ground-water quality parameters and to assess any relationships to CC&V's operations. <br />Threshold criteria, if added to practice-based conditions should be founded on the ambient water- <br />quality data collected to date for parameters that are pertinent to CC&V's operations. Provided <br />the data for the pertinent criteria do not change in a manner that is attributable to CC&V's <br />operations, the data base available to compute ambient water quality will increase with time. <br />The expansion will allow for continuous improvement of the definition of ambient ground water. <br />With specific reference to the proposed numeric criteria of your letter of October 7, 1996, <br />CC&V notes that, when all data are combined for the ground-water wells, one parameter would <br />exceed the proposed criteria on the average and all criteria would be exceeded using the <br />maximum value measured during the period of record. On these bases alone, the proposed <br />criteria would not be practical because exceedences would occur under ambient conditions. <br />When the log-normal distribution of the entire set of measurements is taken into account, in this <br />case by using 5 sigma, every proposed criterion is exceeded. Therefore, there would be a high <br />probability, perhaps greater than 10 percent, that essentially all criteria would be exceeded ig ven <br />the current distributions of concentrations. This would be particularly problematic because it <br />would signify that ambient baseline concentrations were unacceptable -which, of course, is an <br />approach in direct conflict with both the Mined Land Reclamation Board's rules and the Water <br />Quality Control Commission's regulations. <br />The use of practice-based conditions seems most appropriate and they are already in place. <br />2 <br />