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<br /> of the standard value of 12 for irrigation water. Both of these values <br /> would be reduced as a result of mixture with water from the North Fork of <br /> the Purgatoire River before reaching the adjacent Golden Eagle Mine. <br /> Using the apparent additional Q7-10 low flow value of the North fork, <br />~// i.e. 10.9-1.6 or 9.3 cfs, the Purgatoire River below the confluence of <br />(jlrlc the North and Middle Forks would have a TDS value of 236 mg/1 and a SAR <br />,1 <br />~~ value of 4. The downstream use of this water for either domestic or <br />~ <br />~ <br />1~ irrigation purposes should not be affected. <br />~ <br />`~ <br />d <br />~\` At the New Elk Mine site, several historic and existing coal refuse piles <br /> are located on the alluvial flood plain of the Middle Fork of the <br /> Purgatoire River. None of these is now being used by the mine. As a <br /> result of Permit Revision 1, a new refuse disposal area was established <br /> north of the mine across Highway 12. Processing waste is carried to this <br /> facility by means of a conveyor system from the prep plant. This is the <br /> only coal waste disposal facility currently in use at the New Elk Mine. <br /> Runoff and seepage from the new refuse disposal facility is contained by <br /> Pond 8. This pond has never discharged since its construction. <br /> Consequently, except in a rare case of pond discharge, no impact on water <br /> quality in the Middle Purgatoire should be made by runoff and seepage <br /> from this facility. <br />Seepage from the refuse piles located in the alluvial flood plain, <br />however, does enter the stream-alluvial aquifer system where it can <br />affect water quality. An analysis of leachate from the estimated 16.6 <br />acres of this refuse shows the water tom sodium sulfate-bicarbonate <br />type with a total dissolved solids concentration of 2599 mg/1 and a pH of <br />8.0 (Exhibit 6, Table 13). Trace metal concentrations are low. <br />A water balance study was conducted for the New Elk Mine development <br />waste pile site and is contained in Exhibit 6 of the New Elk permit <br />application. In this study, the applicant has calculated the average <br />annual precipitation at the New Elk Mine to be 16.92 inches. Sublimation <br />of snow during winter, and evaporative losses were calculated to be 3.77 <br />inches. During a normal year, runoff from the refuse piles is calculated <br />to account for all of the remaining available precipitation. Based on <br />the calculations <br />included in the application, deep percolation in most years will be <br />essentially zero; that is, all precipitation will evaporate or runoff <br />from the soil. During wet years, as much as .72 inches of water may be <br />attributed to subsurface runoff (See Exhibit 6, pages 44-50 of the permit <br />application). <br />Infiltration of this runoff, based on an estimated 16.6 acres of refuse <br />being present, suggests that a mean flow of 0.001 cfs could issue from <br />the pile. Amass balance calculation using a Q7-10 low flow value of <br />1.6 cfs for the tdiddle Purgatoire and a total TDS value of 204 indicates <br />TDS values in the river would only increase about 2.0 mq/1 as a result of <br />this seepage. Calculation of SAR values for the Middle Purgatoire once <br />this seepage is included also show no appreciable increase. Use of the <br />water for either drinking or irrigation purposes is therefore, not likely <br />to be affected. <br />-24- <br />